Nuclear scanning - the next stage in diagnosing lameness

Nuclear scintigraphy or 'bone scanning' attempts to take lameness diagnosis one stage further by predicting rather than just diagnosing fractures. It is an imaging technique that searches for an increase in bone production and thus can often pinpoint the cuase of minor lameness problems before they become catastrophic injuries.

Nuclear scintigraphy works via the highly ingenious idea of linking a mildly radioactive substance to bone turnover so that it can be measured.  A radioactive substance called technetium is joined together with a phosphorous compound and then injected intravenously into the horse. The bones of the horse use this phosphorous compound to make more bone cells at different rates depending on what is going on in each individual bone. A ‘normal' bone in an adult horse will therefore only take up a small amount of the phosphorous compound and thus only emit a small amount of radiation.  However, a bone with a stress fracture in it will take up lots of the phosphorous compound and therefore emit a large amount of radiation as it attempts to make lots of new bone cells to try and ‘fix' itself.  As a result, the amount of bony remodeling taking place in the equine skeleton can be measured by the amount of radiation emitted from a particular site using a sophisticated radioactivity measurement device called a gamma camera.
After the intravenous injection, providing that the horse is not too lame, it is exercised gently to distribute the compound evenly before its radiation is measured.  Thirty minutes later, the injection leaves the blood and soft tissue and heads for bone, therefore radioactivity readings are taken two to five hours after administration.  Horses must stand still long enough to obtain good readings and so they receive a standing sedation but no general anesthetic is required.  Although simple handheld ‘point' radioactivity scanners can be used to measure the radioactivity, large expensive gamma cameras are much better as they are situated on a steady crane, move all around the horse smoothly and take more accurate readings in a shorter period of time, thus reducing the risk of movement errors.  Bone scans can easily be carried out and analyzed in a day, although horses must remain in controlled areas overnight as they remain slightly radioactive until the next day. This does lead to slight practical disadvantages of nuclear scintigraphy – the safety precautions required when working with radiation and the necessity to stop the horse's work whilst it resides at a nuclear facility.
Nuclear scintigraphy allows for the evaluation of the entire equine skeleton, although specific regions can be imaged as required.  A computer then processes the information from the gamma camera and generates an image of the horse's bones.  Areas of increased radioactivity, which reflect increased bony remodeling, are represented as ‘hot spots.' Although these can simply reflect a normal area of increased bone turnover such as a growth plate in a young horse, a large uptake in a certain place may signify a ‘stress fracture.' A stress fracture is simply a very early fracture that is not displaced in any way.  The bone turnover is high because the bone is trying to ‘fix' itself.  Once a ‘hot spot' has identified where the problem is, x-rays and ultrasound scans can be brought in to further investigate the specific area.
Due to the expense of the equipment and the practical safety issues associated with bone scanning, it is not the sort of equipment that is found at every training center or racetrack.  Even though the radioactivity of the substance is very short-lived, many safety precautions have to be taken. The syringe containing the radioactive injection is protected from the veterinarian administering it by way of a lead shield.  All those coming into contact with the horse from that point onwards wear protective clothing, and the horse's dirty bedding is stored and then disposed of in accordance with strict radiation regulations.
Although many veterinary centers may own a handheld point scanner, the superior gamma cameras are generally found at universities and large veterinary hospitals.  The result is that bone scans are not carried out as routinely as some other less expensive, more readily available imaging techniques.  However, when ‘conventional' imaging techniques such as x-rays and ultrasound scans either fail to find abnormalities or more serious fractures are feared but not seen, then horses should undergo a bone scan.  They are most useful in young horses with severe, acute lameness and they have a number of important uses.
Firstly, their most common use is in the case of a lame horse whose specific problem has not been found by conventional veterinary medicine.  For example, ‘nerve blocks,' which ‘freeze' the leg in specific locations, may have found the area of pain but x-rays and ultrasound scans have not revealed a specific problem. If the bone scan reveals a hot spot in, for example, the lower cannon bone, then the horse is likely to have a stress fracture here. Stress fractures can be so small that in the initial stages they are not visible on x-ray and it is only when the bone has remodeled around the small fracture line that some changes can be seen.  In fact, sometimes a fracture line is never seen at all on x-ray and so nuclear scintigraphy really is the only method by which it can be diagnosed.
Nuclear scintigraphy is also useful in horses with suspected spinal or pelvic pain where x-rays and ultrasound images are inconclusive.  A bone scan can reveal a hot spot that proves the activity of the bone at the suspected location, thus confirming it as the source of pain.  The horse's back is a very difficult area to assess both clinically and using x-rays and ultrasound scans, hence the gap in the market for an influx of miraculous ‘back manipulators' and chiropractors, many of whom have very little scientific basis behind their technique.  A bone scan can prove whether there really is any bony problem behind the horse's pain, for example, a ‘kissing spine' where a horse's back vertebrae ‘rub' together or a pelvic stress fracture.
Trainers also send horses that are moving and performing poorly for full body bone scans as these animals can have multiple sites of pain.  Rather than freezing joints one by one with nerve blocks to try and ascertain which joints hurt most, the bone scan can highlight several mild hot spots, which might be troubling that particular horse.  Following assessment of these areas either clinically or using x-rays and ultrasound scans, some trainers may then choose to have several joints ‘medicated' with anti-inflammatories, lubricants and substances to increase joint health in an attempt to make the horse move more fluently and win more races.
The only drawback with using scintigraphy in this way is that bone turnover does not necessarily correlate perfectly with painful joints. Nuclear scintigraphy has a tendency to over-diagnose problems and label ‘normal' bony remodeling as injuries.  Some joints have lots of bony changes in them but actually cause very little pain or reduction in performance, whilst some very painful joints are actually caused by inflammation of the joint capsule, joint fluid and joint ligaments and thus bony turnover may not actually be increased. Therefore, proving the site of pain by nerve blocking may have in fact been more effective.  When a horse is diagnosed with two sore knees and a sore hind fetlock, we will probably believe it.  However, when horses are diagnosed with three sore joints and four stress fractures, I personally find it hard to believe.
The final important asset of nuclear scintigraphy is the speed with which it can diagnose a fracture.  Sometimes it is urgent to find out immediately whether or not a horse has a fracture. The veterinarian dealing with the horse suspects a fracture but cannot see one on x-ray. Whilst it would be possible to wait and re-x-ray the horse in a few days or weeks, the bone scan gives an instant answer and thus connections know what the problem is with their horse and how it should be treated – as a mild lameness or a fracture that must be rested in order to prevent a catastrophic injury.
At this point, readers are probably wondering why there are not more bone scanning facilities and why they are not used more regularly. This again brings us back to the fact that nuclear scintigraphy measures bone turnover and unfortunately this does not always correlate with fractures.  Whilst a bone scan is highly unlikely to miss a fracture, it may diagnose one when there is not one there. Examples of this include areas of ‘normally' high bone turnover such as growth plates in young horses (bone remodeling associated with growing), ‘bucked' shins that are remodeling but should not be treated as fractures, and some changes associated with large bones such as the radius and the tibia.  The tibia is the equivalent of the human shinbone and in the same way as we can get sore shins, horses can get sore tibias.  When horses begin training, tibias may be remodeling at quite a high rate (and thus will be picked up by a bone scan) but they should not always be treated as fractures. If I were to start road running tomorrow, my shins might become slightly sore after a few days and start to remodel to the increased work. However, rather than stopping, it would actually be better for me to carry on with my running until my shins adapt to their new work. Similarly, bone scans can make us stop training some horses fearing a fracture when they are actually at no higher a risk of fracturing than the horse in the next stall, and in fact, we are just making their bones ‘softer' for when we recommence their training.
In summary, nuclear scintigraphy may be hard for many of us to pronounce but by measuring bone turnover in the equine skeleton, it has become a very useful tool in equine lameness diagnosis. As legendary Breeders' Cup winning trainer Michael Dickinson (my uncle) says: "the phrase that sums up bone scanning is ‘peace of mind.'" There are numerous examples of horses that have had potentially fatal fractures prevented by undergoing a bone scan, which revealed that a minor lameness was actually being caused by a potentially catastrophic fracture.
Thanks to the late Dolly Green, the Southern California Equine Foundation was able to build a nuclear scintigraphy facility at Santa Anita racetrack.  It was this facility that enabled 2007 Kentucky Derby hopeful Ravel to be diagnosed with a stress fracture that could not be found on x-ray.  As trainer Todd Pletcher said, "…it would have turned into a condylar fracture if we had breezed him." Similarly, Halfbridled, the Champion two-year-old filly of 2003, was diagnosed with a stress fracture in a cannon bone and is now safely undertaking her new role as a broodmare.  Nevertheless, bone scans are not perfect.  They can over-diagnose stress fractures, they do come with certain practical safety disadvantages and they are perhaps not one hundred percent accurate at diagnosing joint pain. However, despite these limitations, they have been a great addition to veterinary medicine. They may prevent one or two horses from being trained when they are actually fit to work, but they also prevent great horses like Johar, Ouija Board, Ravel and Halfbridled from fracturing on the racetrack and for this we should be grateful. 


James Tate (26 June 2008 - Issue 6)

Pelvic asymmetry in racehorses - increased risk of injury?

By Nicole Rossa

Steeplechase racing in particular is a high risk sport for the horse. There is currently some fairly extensive research into racehorse injuries and fatalities on the racecourse, with previously published scientific reports on the subject being widely available. The racing industry is aware of the need for such reports, as the industry itself is very much in the public eye with regard to injury rates on the racecourse. 

Lameness is one of the main reasons for wastage in the racehorse industry, and was the reported cause of 68% of total horse days lost to training in a study of racehorses in England (Rossdale et al. 1985). This study also suggested that 10% of all diagnosed lameness cases were caused by tendon injury.  Overstrain injuries to the superficial digital flexor tendon (SDFT) are amongst the most common injuries observed in the athletic horse (Goodship, 1993).  It is therefore important to determine all possible causative factors of SDFT injury so that methods for preventing injury can be implemented as part of a training programme.

Hindquarter Asymmetry


The hindquarters of the horse provide the propulsion, and the forelimbs support 60% of the horse's weight.  Problems affecting the pelvic structure in the horse can lead not only to poor performance, but also to an unlevel gait and to lameness of the hindlimb.  There are to date very few scientific reports on the frequency of hindquarter asymmetries in the horse, although Bathe (2002) found that most hard working horses were likely to have some degree of pelvic asymmetry.   This factor may not always affect performance, as many successful horses have been found to have asymmetry of the pelvis.

Dalin et al. (1985) investigated the hindquarter asymmetry in Standardbred Trotters for any correlation with poor performance. He measured differences in height between the left and right tuber sacrale when the horse was standing square.  Of the 500 horses measured 39 of them showed marked hindquarter asymmetry.  In 30 horses the tuber sacrale was lower on the left, and in 9 horses it was lower on the right.  The asymmetric horses had significantly inferior performance (measured by total earnings) compared to the symmetrical horses.  All the horses were trained and raced in Sweden on a left handed track. The asymmetrical horses were also of significantly larger body size than the symmetrical horses.

In a recent study undertaken by Stubbs et al. (2006) in conjunction with the Hong Kong Jockey Club, a number of racehorses were presented for euthanasia (for injury and/or lameness).  Racing and training details were examined in detail, and a clinical examination was carried out before the horses were euthanased. Following post mortem the thoracolumbar spine and pelvis were dissected out and examined.  Although not part of the study it was noted that asymmetry of the pelvis was prevalent in many of the horses that had been dissected, the reason probably being due to a natural torsion of the pelvis as a result of training and racing on right handed tracks only.

It is suggested that asymmetrical loads on the pelvic structure caused by external factors (such as racetrack), and by internal factors (such as locomotor apparatus pain) may lead to a higher stress being placed on one hindlimb, and as a result lead to the development of pelvic asymmetry which may be apparent as pelvic rotation.  Improper movement patterns of the hindquarters, due to pain caused by overuse or from fatigue, may also result in abnormal alignment of the pelvic structure.  This in turn may then cause overloading on the forelimbs (by off loading the hindquarters) and therefore predisposing the forelimbs to injury.  If this can be proved then surely this would emphasise the importance of correcting pelvic misalignments using manipulation techniques such as chiropractic, osteopathic and myofascial release approaches.  There is some unpublished material available to support the use of McTimoney manipulation methods and other soft tissue manipulation in the correction of pelvic rotation.

Hindquarter asymmetry is often associated with sacroiliac joint lesions or with chronic hindlimb lameness.  The tuber sacrale can appear asymmetrical in clinically normal horses as well as in horses with misalignment of the sacroiliac joint (Dyson, 2004). Horses with longstanding poor performance attributed to chronic sacroiliac damage were investigated by Jeffcott et al. (1985).  The majority of these horses showed some asymmetry of the hindquarters with the tuber coxae and tuber sacrale lower on the same side that the animal was lame on. Hindquarter asymmetry may be due to some tilting or rotation of the pelvis in addition to muscle wastage of one quarter, usually the side the horse is lame on.

Abnormal Alignment 
of the Pelvis


Pelvic rotation or abnormal alignment of the pelvis to the thoracolumbar spine can be measured by the level of the tuber coxae to the ground.  If the horse is unable to produce the propulsion from its hindquarters due to discomfort in the pelvic region, then the forelimbs may be required to provide more horizontal propulsion.  The horse will in effect be pulling himself forward with his forelimbs, rather than pushing from his hindquarters.  This may result in over development of the shoulder muscles, thereby reducing the efficiency of the forelimb movement by adding unnecessary weight.

Unpublished data has suggested a positive relationship between injury to the forelimb stay apparatus and pelvic asymmetry, particularly where the presence of functional asymmetry in the hindquarters was found to be due to pelvic rotation, and not as a result of differences in individual bone lengths of the hindlimb.

Lameness and Compensatory Movement Patterns


The compensatory mechanisms of horses with lameness have been extensively researched and reported.  The potential for secondary injuries resulting from a horse's attempt to compensate for lameness by altering its gait pattern are still unclear.  Clayton (2001) found that when a lame limb is supporting body weight, the horse minimises pain by decreasing the load on that limb, resulting in a compensatory increase in the vertical forces in other limbs.  The compensating limbs are therefore subjected to abnormally high forces, and these may lead to lameness in the compensating limbs.

Uhlir et al. (1997) found that in all cases of diagnosed hindlimb lameness that true lameness of the left hind caused a compensatory lameness of the left fore, and that true stance phase lameness of the left fore caused a compensatory lameness in the right hind.

Tendon Injury
The SDFT is the most frequently injured tendon in horses. 

 In a recent study of steeplechase horses diagnosed with tendon and ligament injuries sustained during training, 89% occurred in the SDFT (Ely et al. 2005).  It has been suggested that an optimum level of exercise is required at an early age for tendon adaptation to training, but with increasing age accumulation of microdamage and localised fatigue, failure to the tendon will occur with increasing exercise (Smith et al. 1999).

The induction of injury to the SDFT occurs when loading overcomes the resistive strength of the tendon. Factors which increase the peak loading of the SDFT, such as weight of rider, ground surface, shoeing, conformation, incoordination, jumping, and speed will act not only to increase the rate of degeneration, but will also increase the risk of the onset of SDFT strain (Smith, 2006).  Therefore the prevention of tendon strain-induced injuries by reducing some of the risk factors that increase loading on the tendon may provide the most satisfactory answer.
Animal Manipulation Techniques
McTimoney Animal Manipulation aims to improve asymmetries through manipulation.  There has been much anecdotal evidence for the benefits of McTimoney Manipulation Techniques on animals (Andrews and Courtney, 1999).  There is anecdotal evidence to suggest that McTimoney and other manipulative therapies can make a difference where veterinary medication has failed (Green, 2006), although the application of manipulation techniques in veterinary medicine may be dependent of further research into the clinical effects of manipulation.

Manipulation techniques are thought to cause muscle relaxation and to correct abnormal motor patterns which may be the result of muscular imbalances and restricted joint motion or altered joint mobility (Haussler, 1999).  There is some unpublished material to support that there are significant changes in the symmetry of the pelvis after the application of McTimoney manipulation techniques, and that there is continued improvement one month after initial treatment.

Current Research into Pelvic Alignment


In a recent unpublished study a group of 40 steeplechase horses in training, all using the same gallop, were measured for pelvic asymmetry. The measurement technique used was a somewhat simple (but reliable) method.  Each horse was measured on flat, level concrete while standing completely square and weight bearing on all four limbs.  Measurements were taken vertically using a horse measuring stick with a spirit level, from the most dorsal aspect of the lateral wing on the ilium (the tuber coxae) to the ground, on the left and right sides.
Various data was collected on each horse, regarding race history, how many races run, whether "bumper" (flat races for steeplechase bred horses), hurdle or steeplechase, prize money earnings, handicap rating, and also brief veterinary history.

The aim of the study was to compare pelvic rotation in 20 sound horses to the incidence and degree of pelvic rotation in a group of 20 horses with SDFT strain in either one or both forelimbs. Both the sound horses and the injured horses were in training with the same trainer, and therefore had used the same gallops, and underwent the same training regime.

Although no significant difference was found in the number of horses with pelvic rotation in sound horses compared with the number of horses with tendon strain, there was a high incidence of pelvic rotation in the group as a whole, with a predominance towards pelvic rotation on the right. This could have been due to training methods or gallops used, and certainly warrants further research.

There was no significant association between side of pelvic rotation and side of forelimb tendon strain, but again warrants further investigation using a larger number of horses.  Due to the prevalence of right side pelvic rotation it would not have been possible to show any significant associations anyway between left and right forelimb injury.

The study did present some trends for age of horse, sex, and race history; showing that the number of horses with pelvic rotation and tendon injury increased with age.  Geldings tended towards a higher incidence of tendon injury, and mares tended towards a higher incidence of pelvic rotation. There were equal numbers of sound and injured horses for each race type, but the degree of pelvic rotation in horses that had fallen was notably larger than in the horses that had not fallen.

Future Studies into Pelvic Asymmetry


The preliminary investigation as described above has formed the basis for further research into abnormal pelvic alignment in racehorses, and whether or not there is any association between side of misalignment and side of forelimb injury.  Further research is due to be carried out with a larger sample of horses, and from different yards, to investigate whether there is any prevalence as to the side of misalignment, or if pelvic alignment is affected by training methods and the use of different gallops and that there is continued improvement one month after initial treatment.

Current Research into Pelvic Alignment


In a recent unpublished study a group of 40 steeplechase horses in training, all using the same gallop, were measured for pelvic asymmetry. The measurement technique used was a somewhat simple (but reliable) method.  Each horse was measured on flat, level concrete while standing completely square and weight bearing on all four limbs.  Measurements were taken vertically using a horse measuring stick with a spirit level, from the most dorsal aspect of the lateral wing on the ilium (the tuber coxae) to the ground, on the left and right sides. Various data was collected on each horse, regarding race history, how many races run, whether "bumper" (flat races for steeplechase bred horses), hurdle or steeplechase, prize money earnings, handicap rating, and also brief veterinary history. The aim of the study was to compare pelvic rotation in 20 sound horses to the incidence and degree of pelvic rotation in a group of 20 horses with SDFT strain in either one or both forelimbs. Both the sound horses and the injured horses were in training with the same trainer, and therefore had used the same gallops, and underwent the same training regime.
Although no significant difference was found in the number of horses with pelvic rotation in sound horses compared with the number of horses with tendon strain, there was a high incidence of pelvic rotation in the group as a whole, with a predominance towards pelvic rotation on the right. This could have been due to training methods or gallops used, and certainly warrants further research.

There was no significant association between side of pelvic rotation and side of forelimb tendon strain, but again warrants further investigation using a larger number of horses.  Due to the prevalence of right side pelvic rotation it would not have been possible to show any significant associations anyway between left and right forelimb injury.

The study did present some trends for age of horse, sex, and race history; showing that the number of horses with pelvic rotation and tendon injury increased with age.  Geldings tended towards a higher incidence of tendon injury, and mares tended towards a higher incidence of pelvic rotation. There were equal numbers of sound and injured horses for each race type, but the degree of pelvic rotation in horses that had fallen was notably larger than in the horses that had not fallen.

Increasing Oxygen Concentration in the Blood of the Racehorse

Oxygen is the fuel of life and its efficient use is the key to athletic fitness. The respiratory system of the racehorse must work hard to harvest the 20 percent of oxygen present in the air we all breathe. Observing a horse after his work on a cold morning provides a visual reminder of this, as the breath surges from his nostrils.

The respiratory process
Glucose and oxygen interact via a process called aerobic respiration, resulting in the production of energy. This cellular process powers all of our bodily functions, from breathing and digesting food to sprinting for the winning line. Carbon dioxide and water are by-products of this reaction.

Cells can also produce energy in the absence of oxygen (anaerobic respiration). In this case, glucose is also broken down to release energy. However, the lactic acid formed by this reaction is a more noxious compound than the carbon dioxide and water created by aerobic respiration. Its presence in cells results in muscle cramps and fatigue.  This lactic acid must be broken down into carbon dioxide and water, but this reaction again requires oxygen. Essentially, anaerobic respiration allows muscles and other cells to function for a short time in the absence of oxygen, building up an ‘oxygen debt.' This must be repaid later to allow the lactic acid to be broken down.
A good measure of a horse's fitness is how quickly breathing and pulse return to normal after exercise. This is because aerobic respiration is more efficient in fit horses, so they build up less of an oxygen debt while exercising. Less oxygen is required to breakdown lactic acid once the work has been completed.
Oxygen is delivered to the body tissues via the respiratory and cardiovascular systems. The respiratory system of the horse includes everything from the nostrils to the lungs. Air is delivered to the lungs, where oxygen diffuses into the bloodstream and is taken up by red blood cells. These cells are the body's carriers for molecules of oxygen and they are pumped around the body by the heart through arteries, capillaries and veins.
Physical causes of inefficient oxygen delivery
Trainers and veterinary surgeons must make sure that all of the components of the respiratory and cardiovascular systems are working to their full potential. This ensures that the body delivers oxygen as efficiently as possible to the muscles, in order that they have the energy necessary to win races!
The following may all be considered surgical conditions of the upper respiratory tract, in that a surgical procedure is often necessary to effect a cure:
Some of the main clinical problems that affect the upper respiratory tract (nostrils, larynx and pharynx) are related to physical obstruction of these ‘tubes.' Anything which reduces the diameter of these tubes will reduce the amount of air, and thus oxygen, which is delivered to the lungs. Physical obstructions of the upper respiratory tract are generally diagnosed by endoscopic examination carried out by a vet. Some conditions, e.g. profound cases of laryngeal hemiplegia, can be seen and thus diagnosed when the horses are at rest. Other conditions only occur when the horse is exercising. In these cases dynamic endoscopy, i.e. endoscopy whilst the horse is actually exercising on a treadmill, may be needed to fully elucidate the problem (Figure 1).
Horses are obliged to breathe through their noses, and cannot breathe through their mouths as many other species can. Sometimes the alar folds (skin folds above the nostrils) are incriminated as the cause of abnormal respiratory noise. Nasal strips are marketed as a means of stopping the soft outer nasal passages collapsing during exercise, thus increasing airflow into the lungs. Relatively common causes of reduced airflow through the nasal passages are space-occupying lesions such as cysts within the sinuses, or vascular growths (ethmoid hematomas). Surgical removal is often necessary.
The pharynx and larynx are other areas which may be affected by conditions which physically restrict the amount of air pulled into the lungs. Probably the best known of these is laryngeal hemiplegia. The larynx is a dynamic structure, which closes to prevent food entering the windpipe and opens to allow air to enter the lungs. Provided that the muscles controlling the larynx are functioning properly, the larynx can be opened to form a diamond-shaped structure. However, it is relatively common for the left side of the larynx to become paralyzed (Figure 2).  This results in only half of the larynx opening, reducing airflow into the lungs. Horses that suffer from this condition often make a characteristic ‘roaring' sound. Surgery is usually indicated to correct this. A laryngeal tieback, whereby a suture is placed through the left side of the larynx to permanently hold it open is often the treatment of choice for roarers. Normal procedure combines this with a ‘hobday' operation, which removes the vocal folds from the larynx and further opens the airway. Treatment for dorsal displacement of the soft palate, another relatively common condition affecting the upper respiratory tract, is more controversial. Some horses respond to conservative management, including the use of drop-over nosebands or tongue ties. Others need more invasive treatment. This may involve producing scar tissue on the soft palate so that it is ‘less floppy,' and thus less likely to displace. Thermocautery of the soft palate under general anaesthetic is an option, but perhaps a more elegant means of achieving this is the use of a laser. This may be performed in the standing, sedated horse. More recently, an operation which mobilizes the larynx to prevent dorsal displacement of the soft palate (‘Tie Forward') has been developed. Other physical conditions that may impede airflow through the pharynx include entrapment of the epiglottis by the folds of soft tissue (aryepiglottic folds) which lie alongside it, and chondritis or inflammation of the cartilages which form the larynx.
Medical causes of inefficient oxygen delivery
A number of medical conditions may also affect the amount of oxygen available to the horse.
Exercise-induced pulmonary hemorrhage (EIPH, or ‘bleeder') is a relatively common condition in which a blood vessel within the lungs bursts, and bleeds into the airways. The severity and amount of blood associated with such an incident can vary markedly. Sometimes relatively large volumes of blood are seen escaping from the horse's nostrils. In other cases, the volume of blood is relatively small and remains confined to the distal airways. This can only be detected after the event by endoscopy and examination of the cell types within the horse's respiratory secretions. Either way, blood takes the place of air within the airways and less oxygen is available to diffuse into the bloodstream. In addition, blood within the airways is a good medium to support bacterial growth and this may predispose horses to bacterial respiratory infections.
The exact cause of EIPH has yet to be elucidated. It may be due to increased blood pressure within the lungs during exercise, concussive damage to the blood vessels as the horse gallops, or a combination of both. Some horses appear to be more prone to this condition than others, and it appears that concurrent respiratory tract infections may also predispose horses to a pulmonary bleed. A variety of treatments have been tried. Furosemide is a diuretic drug, which essentially makes horses urinate more and this in turn dehydrates the horses slightly. It is postulated that this results in less fluid within their circulation and reduced blood pressure within the lung's small capillaries. Its use is permitted on race days by state racing authorities, but this may not be the case forever. However, as a prohibited substance likely to influence performance, it is banned in European racing. In spite of this it retains its place as a drug for training, as when given on work mornings, the chances of a bleed are said to be reduced. Some studies have also suggested that the use of nasal strips may reduce the chance of a bleed occurring, without any untoward side effects. These too are currently banned in European racing but can be used for training purposes. In England, known bleeders often have their water intake restricted before a race in an attempt to reduce blood pressure and thus the chances of a bleed. Clearly, to strike the correct balance between giving the horse sufficient hydration to perform well on the track and lessening the chances of a bleed, the eye of an experienced horseman is required.
Respiratory tract infections may also interfere with optimal oxygenation of the blood. Firstly, infections are associated with an increase in the amount of mucus within the respiratory tract, which may form a physical barrier to airflow and diffusion of oxygen. It is possible to vaccinate against the well-known respiratory viruses, such as influenza and herpes, and some racing authorities require proof of vaccination before a horse can race. However, every horseman will be aware of the non-specific ‘virus,' which results in coughing horses performing at levels below their potential. Viruses may also sensitize the airways, leaving horses more prone to secondary bacterial infections, or post-viral coughs. In addition, it is not uncommon for horses to become anemic following a viral infection. The reduced numbers of circulating red blood cells will lead to sub-optimal oxygen delivery. A number of supplements are available which aim to enable the horses to manufacture more red blood cells.
The importance of good stable hygiene and maintenance of a dust-free environment should not be understated in hastening recovery from airway infections. Even a healthy racehorse should only be exposed to quality roughage feed (good hay or haylage, etc.) and dust-free bedding material.
The cardiovascular system
The heart, which pumps oxygenated blood around the horse's body, must also be in excellent condition to ensure effective oxygen delivery. It should come as no surprise that research has shown that horses which have bigger hearts, as measured by ultrasound, are more likely to perform at the top level. An excellent example of this is the 1973 American Triple Crown winner, Secretariat, whose heart was recorded as weighing 21 lbs. at post mortem. It is clear that horses which have problems with their heart function are likely to perform poorly. The heart must beat in a rhythmic manner to allow coordinated filling of its chambers, followed by a coordinated contraction so that blood is pushed around the body in an efficient manner. Arrhythmias, such as atrial fibrillation, prevent this synchronization and are reflected in disappointing efforts on the racecourse. Diseases of the heart muscle itself (cardiomyopathy), alongside problems with the heart valves and abnormal openings in the walls of the heart are further causes of poor performance. Diagnosis of cardiac conditions may require echocardiography (ultrasonic examination of the heart) to assess the structure of the heart and blood flow within it. Electrocardiographic (ECG) evaluation will identify problems with the heart's rhythm and the electrical activity responsible for setting it.
The act of breathing is fundamental to animal life and so optimal uptake and use of oxygen is the foundation upon which equine training regimes are based. The horse's respiratory system must be fine-tuned to perform to its full potential and the skilled trainer must make himself aware of any problem which may be impeding this.

Barry Sangster 
(14 February 2008 - Issue 7)

Strengthening Young Thoroughbreds' Limbs

One of the major challenges in training racehorses is keeping them sound. Not unlike a human athlete, a racehorse's ligaments, tendons, bones and joints are susceptible to injury throughout its career and, at times, it seems impossible to avoid some sort of musculoskeletal mishap.

A vast number of components can comprise any musculoskeletal injury but many believe the economics of the Thoroughbred industry - namely the preparation of young horses for 2-year-old sales and racing 2-year-olds - are the main culprits for these sorts of injuries.
Training for most race horses commences when they are 18 to 20 months old. The skeleton of a horse often does not reach full maturity until they are four years old so training at a young age might predispose horses to a multitude of career-limiting or -ending injuries.
Shin soreness or bucked shins is an extremely common condition in young racing Thoroughbreds and Quarter Horses (and occasionally Standardbreds.) It involves the front portion of the cannon or metacarpal bone and is the result of rapid bone modeling.
Before a horse begins training, its cannon bones have the same thickness all the way around. When horses start galloping, there is a considerable increase in stress on the front of the cannon bone.  To contend with the stress, the equine body responds by adding new bone to the area in duress. Ultimately, this creates stronger bones but early on this new bone is prone to microfractures similar to the stress fractures that human athletes endure during training.
The severity of bucked shins can vary greatly, but most horses will exhibit pain when the cannon bone area is massaged, will be lame while trotting, and have a short, choppy stride. Another symptom is swelling in this area of the leg.
The condition is usually diagnosed by recognizing the clinical indicators in a horse when it begins its first training and/or racing campaign. Horses suffering from shin soreness must be rested until all signs of lameness have disappeared, which can take several days or many months.
For example, New York-based trainer Barclay Tagg's then 2-year-old colt, Tale of Ekati, had sore shins and returned after a month of light training to triumph in the Grade 2, $250,000 Belmont Futurity on September 15th of last year.
"One shin was very sore, but he got over it very quickly," Tagg said. "I got two real good works into him."
While Maimonides, a 2-year-old, owned by Ahmed Zayat, exited the Grade 1 Hopeful Stakes held at Saratoga Race Course on September 3 with the same affliction, his recovery was expected to take a bit longer. Sonny Sonbol, Zayat's racing manager, said he needed "three to four weeks to get over his shins and start back training and get ready for the winter."
Estimates vary, but it is believed between 65 and 90 percent of all Thoroughbreds in the United States and more than 40 percent of all Thoroughbreds in Australia buck their shins early in training.
About only 12 percent of young English racehorses buck their shins. Unlike the United States and Australia, much less emphasis is placed on 2-year-old racing in England and English horses are trained on straight tracks, so less strain would be placed on the cannon bone.
However, the English are not immune to their young horses being injured. In a study of 314 young Thoroughbreds in Newmarket more than 50 percent experienced some period of lameness, and in roughly 20 percent of those horses, the lameness prevented them from racing.
Also, bucked shins are not exclusively relegated to 2-year-olds but to all horses which are just beginning intense training. Some horses can suffer recurrences of shin soreness after a period of stall of paddock rest. Therefore, bucked shins do not discriminate based on the age of a horse, but depend on how intense the training is and if the horse is undertaking the action for the first time.
Dr. David Nunamaker, VMD, PhD, is an orthopedic surgeon and chair of the research department at the University of Pennsylvania's New Bolton Center who had conducted extensive research on bone development from 1982 to the present. Dr. Nunamaker, Dr. William Moyer, DVM, chair of the Large Animal and Surgery Department at Texas A&M University and Dr. John Fisher, DVM, an equine veterinarian and Maryland horse trainer, analyzed their research results and established a training system created to reduce the severity of bucked shins or erase them.
"We found that a horse's bone shape alters in response to its training," Dr. Nunamaker said. "The way most conventional training is conducted, a bone changes in a way it should not and that is why you get into trouble with bucked shins. Also saucer fractures seem to occur only in horses that have previously bucked their shins. This could lead to catastrophic fracture."
Dr. Nunamaker concluded a problem will become evident after 50,000 cycles of trotting and galloping. A cycle is equal to one swift stride.
"The Standardbred doesn't have issues with bucked shins because you never see a pacer do anything but pace while Thoroughbreds train with a variety of gaits, such as walking, trotting and galloping," Dr. Nunamaker said. "Thoroughbreds do not run while they are training and when they do run it's only every 10 to 14 days. The bone remodels to what it experiences - which is not racing."
Speed work is very important because when a horse runs at speed, the angle of strain is much greater. So horses that breeze more often remodel their bones for racing.
Utilizing the research results, Dr. John Fisher adheres to a training program that stresses and stimulates the cannon gradually.
"When a horse is breezed, the bone sees it as an emergency and immediately begins laying down new bone," Dr. Fisher said. "This new bone is weak and needs to be strengthened through later remodeling, which would be triggered by further breezes spaced closer together. If remodeling is not allowed to take place and the horse is asked to do too much before he is ready, the new bone will be weak and prone to injury. The bone-strengthening is entirely based on stress and recovery to gradually increase bone density and strength."
In Dr. Fisher's program, horses transition from a one furlong work at 15 seconds to a half-mile or more in 13 seconds over a 16-week period.
If there are more than four days between short distance works, Drs. Nunamaker and Fisher have discovered the new bone will stop rebuilding and actually weaken, with no additional stress after five days.
Once the program has been finished, a horse is prepared to begin conventional training because he should have accumulated enough bone strength that he will not buck shins. However, if a horse is subjected to different track conditions or circumferences, such as a European horse racing on American dirt, the threat of shin soreness resurfaces.
Even though Dr. Fisher has modified the program throughout the years, he is still quite pleased with its performance.
"We just don't have many injuries at all," Dr Fisher said. "No more tendons, no more suspensories, no more fractures."
How much high-speed work and distance are required to signal the bone to remodel itself correctly and not form weaker bone? Research is still being conducted but Dr. Nunamaker claims the goal is to correctly change the bone at the slowest possible speed over the shortest possible distance.
 
"Maybe two furlongs, maybe one furlong," Dr. Nunamaker said. "Maybe it won't even have to be that far. We just don't know but there is a fine line during a crucial time period as to what is too much and what is not enough."
Once the bone has attained maximum strength by becoming thicker at its stress points, it should stay that way.
"When we looked at the timing of the injuries that occurred in horses that have shin injuries, we found that when the horse reached four years old, it no longer had shin injuries," Dr. Nunamaker said. "It may develop injuries to other parts of its body, but not to the shins. It is in the first two years of its training program, if it starts at two years of age, that it is going to have shin injury problems. After that no more shin injuries."
It is important to note the bones are the slowest part of the body to train. In most cases, the cardiovascular system and soft tissues are prepared for the stress of racing before the bones.
Study results presented at the 2005 Australian Veterinary Association depict shin soreness or bucked shins can be avoided. Certain training techniques place horses at risk for this condition.
The most significant factor was how far the horse trained and how quickly he went. If a horse trained at a speed greater than 33 mph during its first ten weeks of training, he tended to have some shin pain.
"A gradual increase in the weekly distances at these speeds is the key to reducing the number of cases," Dr. David Evans, BVSc, PhD and associate professor of veterinary science at the University of Sydney and one of the researchers on the project, said.
The study also revealed that using short gallops of 200-300 meters at 33 mph or greater can decrease shin soreness; training horses to induce shin soreness will not reduce the risk of contracting the condition during subsequent training; and shin pain occurred much less often in horses that began training at an average age of 30 months.
Dr. Evans acknowledged that much more research was necessary before any authoritative program could be implemented.
K.L.P. Verheyen, DVM, MSc, PhD, MRCVS, of the Royal Veterinary College (RVC) in London, agrees with Drs. Nunamaker and Evans that training methods are associated with injury risk.
"Stress injuries are repetitive loading injuries," Dr. Verheyen said. "Compare it to a paper clip and if you keep bending it, it will break. Interval training (alternate periods of hard exertion and rest) is a better option because high-speed exercise is as not bad as previously thought. It actually stimulates bone to respond, because bone is a living tissue and is constantly remodeling. If the same exercise is repeated again and again, the bone will stop responding, which is what we think is happening with the low-speed exercise and stress fractures."
While more research must be conducted to provide greater insight into how equine bones adapt and grow, even less is known about how tendons and ligaments respond to training. In a series of recent studies, Allan Goodrich, a professor at the Royal Veterinary College and the University College of London, discovered that the tendons of young horses (less than two years) strengthen in response to training. These results raise the possibility that early training enhances the development of the limb's support structures and could diminish injuries during training and racing.
After reviewing training methods and treatments, it is obvious much more research must be completed before any sound strength management program can be introduced.
"We just don't have all the answers yet," Dr. Nunamaker said.

Kimberly French 
(14 February 2008 - Issue 7)

Tooth Trouble - why regular dentist visits are essential for racehorses

By Kimberley French

The mouth of a Thoroughbred is the principle means of communication between the horse and his rider. Other aids are used as well, but for many, the bit is what determines direction, rate of speed and position or frame in which the horse moves.

The design and function of the horse’s mouth is such that it provides a perfect vehicle for use as a “steering device.” The interdental space allows a bit to lie comfortably without interfering with the normal position of the jaws when they close. Horses are the only domestic animals that have their mouths used in this fashion.

 Dr. Jack Easley, DVM, MS, Diplomat ABVP, who specializes in equine dentistry and resides in Shelbyville, Kentucky, insists the domestication of horses is the prime reason they require dental care.

 “Typically, horses keep their heads on the ground and eat grass 16 hours a day,” Dr. Easley said. “But we keep them in a stall with their heads up and feed them hay, oats and sweet feed. Stabled horses tend to have more problems with periodontal disease and abnormal wear because their teeth have not adapted from their natural forage diet.”
 Dr. Easley recommends preventative dental care long before a young horse is introduced to a bit. “An oral examination should be performed the day a foal is born,” Dr. Easley said. “You want to make sure the jaws match and there is no deformity in the head.”

A foal's deciduous premolars are all in use within the first few weeks of life and can soon start to wear abnormally if they do not mesh properly. While there are orthodontic devices and surgical remedies to correct truly severe over- and under-bites, they are expensive, difficult to maintain and have variable rates of success.

A foal should be examined again when it is weaned to make sure no teeth are missing from trauma, such as a kick in the mouth, and that all teeth are still properly aligned.

Unless there is an obvious problem, such as holding the head to the side, loss of feed while eating, nasal discharge or swelling of the face, jaw or mouth, a horse does not need to be examined again until it is ready to be bitted, which for a Thoroughbred is usually when the horse is a yearling or a 2-year-old.

When a horse is nine months old, all 24 baby teeth are in place. At this age, most horses will also erupt two wolf teeth and the first permanent molar set erupts behind the baby premolars. By the time the foal is a yearling, he has erupted 24 to 30 teeth and all of the deciduous teeth have been “in wear” long enough that their edges are likely very sharp. Deciduous teeth are softer than permanent teeth and wear sharp edges much faster. It is not uncommon for yearlings to have ulcers or lacerations on their cheeks and tongues from these razor-sharp points.
The first consideration prior to placing a bit in a horse’s mouth is to be sure there are no abnormalities within the mouth that may cause discomfort.

“Trainers should have their veterinarians do a performance float of their horse’s teeth before he is broken,” Dr. Mary DeLorey, DVM of Kettle Falls, Washington, said. “They will remove all sharp edges and round the front corners of the first cheek teeth, both upper and lower. This allows more room for mouth tissues and reduces discomfort when the reins are tightened and bit pressure is increased.”

A wolf tooth is a pointy little tooth located in the bit seat of a horse’s mouth. Much like a human appendix, the wolf teeth are evolutionary holdover, with no real function. The crown and root of the tooth are usually quite small.
A horse can get up to four wolf teeth, which are almost always removed during a performance float because they can interfere with bit placement. They often become “blind” or unerupted and can be felt as little bumps in the gums.
A horse's mouth undergoes the largest turnover of deciduous to permanent teeth between the ages of 2 and 3 1/2 years. He will lose two sets of deciduous incisors and shed two sets of premolars, all to be replaced by permanent teeth. He will have already erupted his second set of permanent molars, and the third set may be getting ready to erupt by 3 1/2 years of age.

According to Dr. Jon W. Gieche, DVM, the shedding of baby deciduous teeth is a complex process that can be hastened by normal chewing forces and delayed or accelerated by abnormal chewing forces. If chewing forces are reduced, breakdown might be slowed. If the adult tooth is not present, breakdown occurs anyway, but at a reduced rate. In some teeth without adult counterparts, the deciduous tooth might remain functional for years beyond its normal life.

Premature loss of a deciduous tooth results in abnormal development of the adult tooth and should only be removed if the adult tooth is present or a loose deciduous tooth can easily be wiggled.

If chewing forces are abnormal, tooth attrition is abnormal. In such a situation, eruption is uneven, with some teeth erupting faster than others. The faster erupting teeth become longer than others, resulting in hooks, ramps, steps, and waves. Without outside intervention, these conditions become progressively worse. They can result in many other complications such as cavities, periodontal disease, and pulpitis (inflammation of the dental pulp, which is located in the central cavity of a tooth). This can lead to premature loss of teeth.  

Dr. Easley compares this scenario to human babies cutting their teeth and thinks it’s essential that young Thoroughbreds receive oral exams every six months. “Oftentimes, we are asking horses to perform while they are experiencing the pain and headaches that are similar to a baby’s teething,” Dr. Easley said. “Babies are cranky and can’t sleep at night when their teeth come in. A horse is going through the same thing; it just can’t cry to let us know it’s in pain.”

These signs could indicate a young horse in dental distress:

∙ Loss of feed from the mouth while eating, difficulty chewing or excessive salivation.
∙ Weight loss or loss of body condition.
∙ Large or undigested feed particles (long stem or whole grain) in the manure.
∙ Head tossing, bit chewing, tongue lolling, fighting the bit, resisting the bridle. 
∙ Poor performance, such as lugging in, failure to stop or turn, even bucking.
∙ Foul odor from the mouth and nostrils or traces of blood in the mouth.
∙ Nasal discharge or swelling of the face, jaw or mouth.

While cheek teeth fractures are an unusual occurrence, they can be responsible for many dilemmas for a horse, from difficulty chewing to bad breath and can cause behavioral problems when pressure is placed on the sides of a horse’s face from the reins.

In an attempt to gather more knowledge on the treatment, management and frequency of this condition, the University of Edinburgh, in Scotland, sent a questionnaire to veterinarians and equine dental technicians. The survey results concluded that 147 horses suffered 182 total fractures. More than 70 percent of the fractures occurred in the upper mandible or jaw and where discovered in roughly .07 to 5.9 percent of all horses examined.

Weight loss and food impaction in the inner cheek are acute complications linked to cheek teeth fractures. Thirty-three percent of the horses examined during the study were unable to eat properly, 29 percent experienced biting and other various behavioral problems and 12 percent had halitosis. However, 39 percent of horses that had sustained a cheek tooth fracture presented no symptoms and were discovered through routine dental care.

The most common method of treatment was extraction of the small dental fragment. Other methods of treatment included extraction of the entire tooth; eradicating sharp edges on the fractured tooth; reducing the height of the opposing tooth; referring the case for other treatment; or not treating the tooth in any way.

After treatment, 81 percent of the diagnosed cases had no further symptoms, 13 percent had no clear-cut outcome and only 6 percent still had continuing complications.

In order for horses in training and racing to remain happy and healthy, it is critical to ensure they are able to work and perform in comfort. Comprehensive dental care delivered regularly by an experienced veterinary professional may be one of the easiest ways to maximize a horse’s performance and optimize his health for a lifetime.

Hoof Matters - concentrating on the foot rather than the shoe

In 1889, for the fourth edition of his book “The Racehorse in Training with Hints on Racing and Racing Reforms”, the English jockey turned horse trainer William Day added a chapter on shoeing, his preface stating “…one topic, highly important to all owners of horses, ‘Shoeing’…might advantageously be added…the aim to deal with facts and to avoid speculation.” Day wraps up by adding that he hopes “it will be found…that the best method of shoeing and of the treatment of the foot has been not only discussed but actually verified… that the prevention which, in the diseases of the feet…is better than cure and has been placed nearer the reach of all.”

If only. Nearly 120 years after Day and his book, the “cure” for many horsemen plagued regularly by a variety of hoof ailments and issues seems as far out of reach as ever. With quarter cracks as common as quarter poles, horsemen particularly in North America continue to play out a modern day version of Cinderella, looking for the shoe that leads to happily ever after, or at the very least, to happy and sound on the racetrack.

Among farriers, veterinarians and trainers there appears to be little agreement and much speculation when it comes to the shoeing of Thoroughbreds. With no “best method” at hand, everyone can, in theory, agree with the familiar adage “no foot, no horse”. But there is great controversy surrounding how to go about improving horse hooves and preventing injury, or even why horses have so many hoof-related problems in the first place. When it comes down to the sole of the matter, at the end of the day, hoof care may well turn out to be the Achilles Heel of the Thoroughbred racing industry.

Most recently, the break-down and subsequent death of Kentucky Derby winner Barbaro brought the topic of equine injuries, and, more specifically, laminitis, to the forefront. Since Barbaro, American racetracks have spent millions installing synthetic surfaces, all espoused to be safer and more cushioned for horses. A record $1.1 million distributed this year by the Grayson-Jockey Club Research Foundation to numerous equine research projects may also be a direct result of the late champion’s demise. Last autumn, the foundation designated a Hoof Care and Shoeing Task Force, another possible throw-back to Barbaro and the subsequent focus on equine injuries.

In the task force’s first official report this past April, prominent owner and breeder Bill Casner outlined one possible cause of injuries in “The Detrimental Effects of Toe Grabs: Thoroughbred Racehorses at Risk”. Endorsed by the Jockey Club, the Grayson Foundation and the Kentucky Horseshoeing School, the report placed the lion’s share of the blame for catastrophic injuries - and hoof-related issues - on the use of toe grabs in horse shoeing. Thoroughbred anatomy plays a role, according to the report: the fact that bone structure and hoof walls aren’t matured in the average racehorse; also the length of pastern or the type of hoof.

The report also briefly mentions harder racetrack surfaces. But the overwhelming research revolved around the link between injuries and toe grabs. Such thinking, according to at least one long-time farrier, may be what’s keeping the industry from finding Cinderella’s shoe. A self-proclaimed maverick, “as far out there as I can be,” North Carolina-based farrier David Richards believes rather than looking at the shoe, researchers should look at the foot. Richards has been shoeing horses for the last 30 years. When asked what type or breed of horse he specializes in, the farrier replies “lame ones”. According to Richards, around 20 to 30 percent of the horses he works on annually are Thoroughbreds. Seventy to 90 percent of all the lameness problems he sees, according to Richards, are related to the hoof wall. “We need to look more at hoof wall as a site of failure,” the farrier says, a principal which has become the backbone of “Equicast,” a product Richards has been developing and marketing for nearly 20 years. The cast, a tape-like, fiber-glass blend, covers the hoof, extending up to the hairline at the coronet band, with a shoe attached either on top of, or beneath, the cast. Its creator likens it to a walking cast in humans, with the event that Thoroughbreds are able to exercise while wearing it, although “there’s a big difference between hoof and human bone.” “The key is managing lateral expansion,” Richards elaborates, “to prevent an overload of the hoof wall, causing hoof problems and pain. The hoof wall is the point of least resistance.” The cast “provides additional support and relieves pressure on the hoof wall,” he says, adding that his product minimizes heat and moisture, factors that also play a role in weakening hoof walls. “When you adhere a shoe to a foot, you are frequently encapsulating bacterial materials,” the farrier offers. “Also, most apoxies are heat generating, and the hoof wall is already a great conductor of heat.”

Common solutions such as vitamin or feed supplements have a minimal effect at best, according to Richards. “The huge problem with any of that is that horses have very poor circulation to their feet.” Circulation issues cause problems all of their own in terms of growth and healing, but they also minimize the effect of anything ingested making a difference. Richards believes a host of factors contribute to a general weakening of the structure of the hoof wall, “a complex and sometimes contradictory” situation that covers nearly everything wrong with feet, from quarter cracks to long toe-low heel to medial lateral imbalances and White Line Disease. “There’s actually no problem in growing feet,” he offers. “The problem is in growing strong feet. “We definitely see a more volatile foot today,” he concedes, citing feeding programs that cause quicker growth, synthetic surfaces that don’t stress the feet enough, and trends in commercial breeding as just a few of the possible contributing factors. “One of the things we’re doing wrong, we’re not stressing the feet enough,” he says. “From the day that they’re born we’re coddling the foot.” “I’ve never heard of a breeder breeding for feet,” Richards adds. “I can think of one really prominent sire that’s a classic example. I have four young horses by the same sire. Four babies right now that already have conformational issues. The sire has a great mind, tremendous ability. But his foals aren’t known for their feet.” “You can’t knock it,” he continues. “But you have to accept the ramifications.” And figure out how to deal with them. Richards looks to external factors as much as internal as a source of the problems.

“Horses who run almost exclusively on turf don’t have half the problems as horses who run on sand,” he says. “They don’t have the shock factor. It’s unfortunate, but if something doesn’t stimulate feet to get harder, they get softer.” Another factor Richards feels may contribute to weaker hoof walls is moisture. “Feet problems are something plaguing all horses evenly, from coast to coast,” he says. “Very little else is constant. Feed differs East to West, other things are different. One thing that’s constant, moisture. And variables of moisture.” Richards laments the fact that little has been done to research the effect of moisture on feet, or whether different parts of the hoof, or different types of hooves, absorb water differently. He’s currently doing his own research on white hooves to see how they react to moisture and believes it may lead to some answers for common problems. “The industry is very grand-fathered in mentality,” he says. “It’s ‘my father did it that way, and his father did it that way.’ There’s a resistance to new products,” he continues. “The diagnostics now have surpassed the treatment. We’re always working with the result of the cause, rather than looking for the cause itself. We’re looking through the answer, for the answer.” Looking down, rather than up, is another part of the problem according to Richards, “The goal is to balance the horse,” he offers. “It doesn’t matter what the sport, you’re ultimately judged on symmetry. There are times when I’m trying to figure out what’s wrong with a horse’s feet, instead of looking down at the foot, I look up to see which shoulder is higher. I’m one of a very few who are cognizant of the whole foot - not just the heel and the toe,” and just as important, how the whole foot fits with the rest of the horse. Richards explains that the majority of the horses he looks at have one leg longer than the other, either from birth or wear and tear.

He goes on to explain that the average 1,000 lb horse exerts 54 lb’s per square inch on the hoof wall with every stride. When that horse is shod, Richards says, the weight on the hoof wall is nearly doubled, to 95 lb per square inch. A typical racing plate exacerbates the problem even more. “We need to transition out of the conventional shoe,” he says. “We are overloading the coronary band.” “One of my criticisms of the industry,” he continues, “there is a total misunderstanding of what foot issues really are. Feet are no man’s land.” “Shoes haven’t changed much over the years,” he adds. “They’re prettier, but they’re going the wrong way. They mask the problems rather than reverse them. The horse may have a longer life on the track, but not a more productive or sounder one.” “It’s a horrible misnomer to say shoes are corrective,” Richards continues. “They’re not corrective. They are totally protective,” a line of thinking which supports the barefoot practitioners, who believe in eliminating shoes entirely at least part of the time. “I’m a huge proponent of it,” he says. “A horse should be totally comfortable doing his respective sport barefoot. The foot is much better at managing us than we are at managing the foot with conventional methods.”

And while at least a few trainers are known to place blame on farriers, Richards holds veterinarians just as accountable, as they are generally the ones who actually diagnose the problems. “They know what’s wrong, but they often don’t know how to treat it,” he says. But in defense of the vets, “there’s a lot of misinformation and a lack of communication.” Perhaps the biggest culprit, from Richards perspective, is a close-mindedness and lack of commitment to the finding the cause of the problem and fixing it. “There are a lot of things we need to do as an industry,” he says. “As an industry, we need to set a standard. There should be an orthopedic certification program, for example, that’s taught to both vets and to farriers. The vets will have to dummy down a little and the farriers will have to bone up.” “But a lot of this is just common sense. A horse with a foot bothering him is like having a tire with too little air in. You wouldn’t drive a car with less air in one tire, you’d fix the tire. You wouldn’t sit in a chair with one leg shorter than the others.” Richards believes we ask our horses to perform that way all the time. He believes at least some of the money for research should be re-allocated, or new money dedicated specifically to hoof issues.

“What we need is to fix a flat.” “How much more does New Bolton really need?” he asks referring to the clinic that treated Barbaro through his final days and has since received hundreds of thousands of dollars in donations for research. “Problems evolve for a reason,” says Richards, who believes the reason almost always rests in the hoof wall. “If we find an effective way to address the problem, it will make a difference that could be revolutionary.” A difference hundreds of years in the making.

Tooth Trouble - why regular dentist visits are essential for racehorses

The mouth of a Thoroughbred is the principle means of communication between the horse and his rider. Other aids are used as well, but for many, the bit is what determines direction, rate of speed and position or frame in which the horse moves.

The design and function of the horse’s mouth is such that it provides a perfect vehicle for use as a “steering device.” The interdental space allows a bit to lie comfortably without interfering with the normal position of the jaws when they close. Horses are the only domestic animals that have their mouths used in this fashion. Dr. Jack Easley, DVM, MS, Diplomat ABVP, who specializes in equine dentistry and resides in Shelbyville, Kentucky, insists the domestication of horses is the prime reason they require dental care. “Typically, horses keep their heads on the ground and eat grass 16 hours a day,” Dr. Easley said. “But we keep them in a stall with their heads up and feed them hay, oats and sweet feed. Stabled horses tend to have more problems with periodontal disease and abnormal wear because their teeth have not adapted from their natural forage diet.”

Dr. Easley recommends preventative dental care long before a young horse is introduced to a bit. “An oral examination should be performed the day a foal is born,” Dr. Easley said. “You want to make sure the jaws match and there is no deformity in the head.” A foal’s deciduous premolars are all in use within the first few weeks of life and can soon start to wear abnormally if they do not mesh properly. While there are orthodontic devices and surgical remedies to correct truly severe over- and under-bites, they are expensive, difficult to maintain and have variable rates of success. A foal should be examined again when it is weaned to make sure no teeth are missing from trauma, such as a kick in the mouth, and that all teeth are still properly aligned. Unless there is an obvious problem, such as holding the head to the side, loss of feed while eating, nasal discharge or swelling of the face, jaw or mouth, a horse does not need to be examined again until it is ready to be bitted, which for a Thoroughbred is usually when the horse is a yearling or a 2-year-old. When a horse is nine months old, all 24 baby teeth are in place. At this age, most horses will also erupt two wolf teeth and the first permanent molar set erupts behind the baby premolars. By the time the foal is a yearling, he has erupted 24 to 30 teeth and all of the deciduous teeth have been “in wear” long enough that their edges are likely very sharp. Deciduous teeth are softer than permanent teeth and wear sharp edges much faster. It is not uncommon for yearlings to have ulcers or lacerations on their cheeks and tongues from these razor-sharp points.

The first consideration prior to placing a bit in a horse’s mouth is to be sure there are no abnormalities within the mouth that may cause discomfort. “Trainers should have their veterinarians do a performance float of their horse’s teeth before he is broken,” Dr. Mary DeLorey, DVM of Kettle Falls, Washington, said. “They will remove all sharp edges and round the front corners of the first cheek teeth, both upper and lower. This allows more room for mouth tissues and reduces discomfort when the reins are tightened and bit pressure is increased.” A wolf tooth is a pointy little tooth located in the bit seat of a horse’s mouth. Much like a human appendix, the wolf teeth are evolutionary holdover, with no real function. The crown and root of the tooth are usually quite small. A horse can get up to four wolf teeth, which are almost always removed during a performance float because they can interfere with bit placement. They often become “blind” or unerupted and can be felt as little bumps in the gums. A horse’s mouth undergoes the largest turnover of deciduous to permanent teeth between the ages of 2 and 3 1/2 years. He will lose two sets of deciduous incisors and shed two sets of premolars, all to be replaced by permanent teeth. He will have already erupted his second set of permanent molars, and the third set may be getting ready to erupt by 3 1/2 years of age.

According to Dr. Jon W. Gieche, DVM, the shedding of baby deciduous teeth is a complex process that can be hastened by normal chewing forces and delayed or accelerated by abnormal chewing forces. If chewing forces are reduced, breakdown might be slowed. If the adult tooth is not present, breakdown occurs anyway, but at a reduced rate. In some teeth without adult counterparts, the deciduous tooth might remain functional for years beyond its normal life. Premature loss of a deciduous tooth results in abnormal development of the adult tooth and should only be removed if the adult tooth is present or a loose deciduous tooth can easily be wiggled. If chewing forces are abnormal, tooth attrition is abnormal. In such a situation, eruption is uneven, with some teeth erupting faster than others. The faster erupting teeth become longer than others, resulting in hooks, ramps, steps, and waves. Without outside intervention, these conditions become progressively worse. They can result in many other complications such as cavities, periodontal disease, and pulpitis (inflammation of the dental pulp, which is located in the central cavity of a tooth). This can lead to premature loss of teeth.

Dr. Easley compares this scenario to human babies cutting their teeth and thinks it’s essential that young Thoroughbreds receive oral exams every six months. “Oftentimes, we are asking horses to perform while they are experiencing the pain and headaches that are similar to a baby’s teething,” Dr. Easley said. “Babies are cranky and can’t sleep at night when their teeth come in. A horse is going through the same thing; it just can’t cry to let us know it’s in pain.” These signs could indicate a young horse in dental distress: • Loss of feed from the mouth while eating, difficulty chewing or excessive salivation • Weight loss or loss of body condition • Large or undigested feed particles (long stem or whole grain) in the manure • Head tossing, bit chewing, tongue lolling, fighting the bit, resisting the bridle • Poor performance, such as lugging in, failure to stop or turn, even bucking • Foul odour from the mouth and nostrils or traces of blood in the mouth • Nasal discharge or swelling of the face, jaw or mouth •

While cheek teeth fractures are an unusual occurrence, they can be responsible for many dilemmas for a horse, from difficulty chewing to bad breath and can cause behavioural problems when pressure is placed on the sides of a horse’s face from the reins In an attempt to gather more knowledge on the treatment, management and frequency of this condition, the University of Edinburgh, in Scotland, sent a questionnaire to veterinarians and equine dental technicians. The survey results concluded that 147 horses suffered 182 total fractures. More than 70 percent of the fractures occurred in the upper mandible or jaw and where discovered in roughly .07 to 5.9 percent of all horses examined. Weight loss and food impaction in the inner cheek are acute complications linked to cheek teeth fractures.

Thirty-three percent of the horses examined during the study were unable to eat properly, 29 percent experienced biting and other various behavioural problems and 12 percent had halitosis. However, 39 percent of horses that had sustained a cheek tooth fracture presented no symptoms and were discovered through routine dental care. The most common method of treatment was extraction of the small dental fragment. Other methods of treatment included extraction of the entire tooth; eradicating sharp edges on the fractured tooth; reducing the height of the opposing tooth; referring the case for other treatment; or not treating the tooth in any way. After treatment, 81 percent of the diagnosed cases had no further symptoms, 13 percent had no clear-cut outcome and only 6 percent still had continuing complications.

In order for horses in training and racing to remain happy and healthy, it is critical to ensure they are able to work and perform in comfort. Comprehensive dental care delivered regularly by an experienced veterinary professional may be one of the easiest ways to maximise a horse’s performance and optimize his health for a lifetime.

Hoof Matters - concentrating on the foot rather than the shoe

By Caton Bredar

In 1889, for the fourth edition of his book “The Racehorse in Training with Hints on Racing and Racing Reforms”, the English jockey turned horse trainer William Day added a chapter on shoeing, his preface stating 
“…one topic, highly important to all owners of horses, ‘Shoeing’…might advantageously be added…the aim to deal with facts and to avoid speculation.”

Day wraps up by adding that he hopes “it will be found…that the best method of shoeing and of the treatment of the foot has been not only discussed but actually verified… that the prevention which, in the diseases of the feet…is better than cure and has been placed nearer the reach of all.”
If only.

Nearly 120 years after Day and his book, the “cure” for many horsemen plagued regularly by a variety of hoof ailments and issues seems as far out of reach as ever. With quarter cracks as common as quarter poles, horsemen particularly in North America continue to play out a modern day version of Cinderella, looking for the shoe that leads to happily ever after, or at the very least, to happy and sound on the racetrack.   Among farriers, veterinarians and trainers there appears to be little agreement and much speculation when it comes to the shoeing of Thoroughbreds.

With no “best method” at hand, everyone can, in theory, agree with the familiar adage “no foot, no horse”.  But there is great controversy surrounding how to go about improving horse hooves and preventing injury, or even why horses have so many hoof-related problems in the first place.  When it comes down to the sole of the matter, at the end of the day, hoof care may well turn out to be the Achilles Heel of the Thoroughbred racing industry.

Most recently, the break-down and subsequent death of Kentucky Derby winner Barbaro brought the topic of equine injuries, and, more specifically, laminitis, to the forefront.  Since Barbaro, American racetracks have spent millions installing synthetic surfaces, all espoused to be safer and more cushioned for horses.  A record $1.1 million distributed this year by the Grayson-Jockey Club Research Foundation to numerous equine research projects may also be a direct result of the late champion’s demise.
Last autumn, the foundation designated a Hoof Care and Shoeing Task Force, another possible throw-back to Barbaro and the subsequent focus on equine injuries. In the task force’s first official report this past April, prominent owner and breeder Bill Casner outlined one possible cause of injuries in “The Detrimental Effects of Toe Grabs: Thoroughbred Racehorses at Risk”.  Endorsed by the Jockey Club, the Grayson Foundation and the Kentucky Horseshoeing School, the report placed the lion’s share of the blame for catastrophic injuries - and hoof-related issues - on the use of toe grabs in horse shoeing. Thoroughbred anatomy plays a role, according to the report: the fact that bone structure and hoof walls aren’t matured in the average racehorse; also the length of pastern or the type of hoof. The report also briefly mentions harder racetrack surfaces. But the overwhelming research revolved around the link between injuries and toe grabs.

Such thinking, according to at least one long-time farrier, may be what’s keeping the industry from finding Cinderella’s shoe. A self-proclaimed maverick, “as far out there as I can be,” North Carolina-based farrier David Richards believes rather than looking at the shoe, researchers should look at the foot.
Richards has been shoeing horses for the last 30 years.  When asked what type or breed of horse he specializes in, the farrier replies “lame ones”. According to Richards, around 20 to 30 percent of the horses he works on annually are Thoroughbreds.  Seventy to 90 percent of all the lameness problems he sees, according to Richards, are related to the hoof wall.
“We need to look more at hoof wall as a site of failure,” the farrier says, a principal which has become the backbone of “Equicast,” a product Richards has been developing and marketing for nearly 20 years. The cast, a tape-like, fiber-glass blend, covers the hoof, extending up to the hairline at the coronet band, with a shoe attached either on top of, or beneath, the cast.  Its creator likens it to a walking cast in humans, with the event that Thoroughbreds are able to exercise while wearing it, although “there’s a big difference between hoof and human bone.”

“The key is managing lateral expansion,” Richards elaborates, “to prevent an overload of the hoof wall, causing hoof problems and pain. The hoof wall is the point of least resistance.”  The cast “provides additional support and relieves pressure on the hoof wall,” he says, adding that his product minimizes heat and moisture, factors that also play a role in weakening hoof walls.
“When you adhere a shoe to a foot, you are frequently encapsulating bacterial materials,” the farrier offers. “Also, most apoxies are heat generating, and the hoof wall is already a great conductor of heat.”

Common solutions such as vitamin or feed supplements have a minimal effect at best, according to Richards.  “The huge problem with any of that is that horses have very poor circulation to their feet.”  Circulation issues cause problems all of their own in terms of growth and healing, but they also minimize the effect of anything ingested making a difference. 
Richards believes a host of factors contribute to a general weakening of the structure of the hoof wall, “a complex and sometimes contradictory” situation that covers nearly everything wrong with feet, from quarter cracks to long toe-low heel to medial lateral imbalances and White Line Disease.
“There’s actually no problem in growing feet,” he offers.  “The problem is in growing strong feet.
“We definitely see a more volatile foot today,” he concedes, citing feeding programs that cause quicker growth, synthetic surfaces that don’t stress the feet enough, and trends in commercial breeding as just a few of the possible contributing factors.
“One of the things we’re doing wrong, we’re not stressing the feet enough,” he says.  “From the day that they’re born we’re coddling the foot.”

“I’ve never heard of a breeder breeding for feet,” Richards adds. “I can think of one really prominent sire that’s a classic example.  I have four young horses by the same sire. Four babies right now that already have conformational issues. The sire has a great mind, tremendous ability.  But his foals aren’t known for their feet.”
“You can’t knock it,” he continues.  “But you have to accept the ramifications.”  And figure out how to deal with them.
Richards looks to external factors as much as internal as a source of the problems. “Horses who run almost exclusively on turf don’t have half the problems as horses who run on sand,” he says. “They don’t have the shock factor.  It’s unfortunate, but if something doesn’t stimulate feet to get harder, they get softer.”

Another factor Richards feels may contribute to weaker hoof walls is moisture.  “Feet problems are something plaguing all horses evenly, from coast to coast,” he says.  “Very little else is constant.  Feed differs East to West, other things are different. One thing that’s constant, moisture.  And variables of moisture.” Richards laments the fact that little has been done to research the effect of moisture on feet, or whether different parts of the hoof, or different types of hooves, absorb water differently. He’s currently doing his own research on white hooves to see how they react to moisture and believes it may lead to some answers for common problems.
“The industry is very grand-fathered in mentality,” he says.  “It’s ‘my father did it that way, and his father did it that way.’  There’s a resistance to new products,” he continues. “The diagnostics now have surpassed the treatment. We’re always working with the result of the cause, rather than looking for the cause itself.  We’re looking through the answer, for the answer.” 
Looking down, rather than up, is another part of the problem according to Richards, “The goal is to balance the horse,” he offers.  “It doesn’t matter what the sport, you’re ultimately judged on symmetry.  There are times when I’m trying to figure out what’s wrong with a horse’s feet, instead of looking down at the foot, I look up to see which shoulder is higher. I’m one of a very few who are cognizant of the whole foot - not just the heel and the toe,” and just as important, how the whole foot fits with the rest of the horse.


Richards explains that the majority of the horses he looks at have one leg longer than the other, either from birth or wear and tear.  He goes on to explain that the average 1,000 lb horse exerts 54 lb’s per square inch on the hoof wall with every stride.  When that horse is shod, Richards says, the weight on the hoof wall is nearly doubled, to 95 lb per square inch. A typical racing plate exacerbates the problem even more.
“We need to transition out of the conventional shoe,” he says. “We are overloading the coronary band.”
“One of my criticisms of the industry,” he continues, “there is a total misunderstanding of what foot issues really are.  Feet are no man’s land.”
“Shoes haven’t changed much over the years,” he adds. “They’re prettier, but they’re going the wrong way.  They mask the problems rather than reverse them.  The horse may have a longer life on the track, but not a more productive or sounder one.”
“It’s a horrible misnomer to say shoes are corrective,” Richards continues. “They’re not corrective.  They are totally protective,” a line of thinking which supports the barefoot practitioners, who believe in eliminating shoes entirely at least part of the time.
“I’m a huge proponent of it,” he says.  “A horse should be totally comfortable doing his respective sport barefoot. The foot is much better at managing us than we are at managing the foot with conventional methods.”
And while at least a few trainers are known to place blame on farriers, Richards holds veterinarians just as accountable, as they are generally the ones who actually diagnose the problems.
“They know what’s wrong, but they often don’t know how to treat it,” he says.  But in defense of the vets, “there’s a lot of misinformation and a lack of communication.”   
Perhaps the biggest culprit, from Richards perspective, is a close-mindedness and lack of commitment to the finding the cause of the problem and fixing it.

“There are a lot of things we need to do as an industry,” he says.  “As an industry, we need to set a standard.  There should be an orthopedic certification program, for example, that’s taught to both vets and to farriers. The vets will have to dummy down a little and the farriers will have to bone up.” “But a lot of this is just common sense.  A horse with a foot bothering him is like having a tire with too little air in.  You wouldn’t drive a car with less air in one tire, you’d fix the tire.  You wouldn’t sit in a chair with one leg shorter than the others.”
Richards believes we ask our horses to perform that way all the time.  He believes at least some of the money for research should be re-allocated, or new money dedicated specifically to hoof issues.  “What we need is to fix a flat.”
“How much more does New Bolton really need?” he asks referring to the clinic that treated Barbaro through his final days and has since received hundreds of thousands of dollars in donations for research.  
“Problems evolve for a reason,” says Richards, who believes the reason almost always rests in the hoof wall.  “If we find an effective way to address the problem, it will make a difference that could be revolutionary.”
A difference hundreds of years in the making.

''Jarred Up'' horses - observations by a racecourse farrier

At the height of the flat racing season how many different terms are used to describe horses that lose their action? The description depends very much upon those that are explaining the condition and what is perceived to be the cause and the effect; the animal simply becomes scratchy and non free flowing in its movements. The exciting cause reveals itself as being “JARRED UP.”

At this early stage no observable foot specific secondary condition is presented. The physical condition I have become aware of horizontal striation of the dorsal wall which is rarely present in two year olds, but as a condition is fairly common in the older three year old plus groups, specifically when the animals have raced the previous season on firm ground. I feel there are several diagnostic constants which mix the primary causes of being “jarred up” with the secondary effects to form the description and source of the discomfort, these can be incorrectly described.

I feel the primary cause of the loss of action often relates to horses’ feet and acute inflammatory changes. The conclusions are drawn from physiological changes noted and only recently considered as being relevant to a loss of action some six to ten months earlier. The early foot changes are demonstrated by irregular growth patterns in the development of the dorsal surface of the hoof wall and related voids within the actual structure of the hoof. The above features progress downward locked in the structure of the hoof wall during normal growth from their area of formation, which was initially located within the tissues of the coronary crown down towards the hoof’s bearing surface. Voids are only revealed physically and visually when the attendant ridging and grooving reach ground level.

Without doubt the observations, when applied to flat racehorses, relate to an incident or repeated incidents of athletic output during the previous racing season on ground conditions unsuitable for the specific animal or its specific physiology. The animal often simply presents as not being free moving without any observable unilateral lameness. Often a few days on “The Walker” at rest and an analgesic course of medication will enable the animal to keep racing throughout the season and without any apparent loss of form, yet the animal’s action is changed and varies from slightly off to quite uncomfortable. To continue to race demonstrates just how adaptable a racehorse is.

I will attempt to describe the primary action modification most commonly noticed. My peers have long since suggested horses prepare their feet to land by lateral and medial adduction and abduction prior to their foot planting, a flaccid lower limb state, probably seeking out the nature of the ground surface and what adjustment the horse has to make to avoid injury. I have noted that the landing preparation aspect of the stride of sore / jarred up horses is dramatically visually bi-laterally exaggerated and the animal instead of abducting/adducting its feet actually assumes a base wide flight and its feet immediately prior to landing describe circular movements away from its axis, the left foot anti clockwise, the right foot clockwise. The movement described is bi-laterally matched, symmetric, which is felt is abnormal and forwards progress for the animal is somewhat mechanical [not free flowing], yet the animal is not exhibiting any unilateral [single leg] lameness. The above is felt is an outline of the noted condition, but what is actually happening? I feel there is strong evidence of coronary shunting, effected by the concussive forces transmitted through the dorsal wall of the hoof into the sensitive tissues of the coronary cushion due to a firm racing surface. It is these concussive forces that cause the coronary corium to lay down a protective fluid barrier, a “CORONARY SEROMA” [blister] or even in the most severe insults “HAEMATOMA” [blood blister], the fluids protect and buffer the vital horn growth area. It follows that this fluid area effectively becomes locked within the growing structures of the dorsal wall. The lymphatic system fairly rapidly mops up the fluid, a cellular, sometimes bloodstained and often linier void remains [non cellular] within the structure of the wall. The severity of the initial physiological insult determines the extent of the fluid, seroma/haematoma and the resultant defective area/void. The weakened hollow area now below the coronary ring is, I feel another of nature’s ways to effect an additional buffering/flexibility to dissipate any future or ongoing shunting trauma, firstly protected by a hydraulic action then an air buffered flexible space which remains within the horn tissue, a perfect and natural response for concussive protection.

The problems of shoe attachment to defective horn are at this stage are effectively still latent. How it affects the tradesman “Abraded feet” is a fairly loose term to describe the ultimate nightmare for the racetrack farrier. The distal edge of the hoof capsule has become flaky, cracked, underrun with cavities, to a greater degree loose from its underlying and adjacent supporting structures. The sole is consistently doubled, one of nature’s processes to protect the solar surface of the distal phalanx [P3] and its related soft tissues. This thickened sole is often not sufficiently matured to be mechanically exfoliated, yet it hangs below the level of the wall.

Nature takes no account within its physiological blueprint for the need of the farrier to attach a metal shoe as a base plate. The increased thickness of the double sole creates stressing forces of its own, demonstrated by the perfectly natural sideways loading on the weakened wall and to complete natural the separation of the already partly separated base structures prior to rebuilding them, which often is further demonstrated by the presence of a dorsal depression in the wall.

This is saying nothing of the now inflexible nature of the doubled sole constricting the natural processes of the sole connective tissues. It must be remembered in the wild state this horse would be somewhat in a recovery state and acutely in danger of predation. The problem is these feet seldom support a shoe in a satisfactory way. Racing plates tend to become easily detached especially during transit to the racecourse. This is a headache for the racetrack farrier, as in order to reattach a shoe, which he is employed to do, the loose unviable horn and great deal of the remaining poorly integrated glue has to be removed, just as is outlined as one of nature’s processes in the above paragraph in order to get a satisfactory layer to load a shoe onto and re-attach, nail the plate into. The problem here is that often after the defective horn is removed there is left insufficient wall horn, both in quantity and quality, into which a nail can be driven, certainly other than in the most forwards toe area and maybe one nail in each heel area. Otherwise, no viable nail supporting wall horn remains.

The thickened solar plate can in the very short term be used by a farrier to assist with a semi-secure nail attachment, as is demonstrated by the system of very low nailing and close shoe fitting sometimes seen in US stock. With ingenuity, stealth a great deal of luck and some skill a failure to reattach a shoe for the purpose of a single race is extremely rare, in my case twice in twenty six years, once due to the extreme stroppy nature of the patient not permitting re-attachment without displacing the re-attached shoe by immediately kicking it off again. The other occasion the animal was still as lame after re-attachment as it had been with the shoe absent when it arrived at the track!

Just out of interest, occasions have arisen when horses have gone to post with the nailing supported with electrical insulating tape, a very useful tool to have in the van and at other times the shoe and nailing supported in place with multiple layers of vet wrap. What happens after the animal returns to the care of its yard is fortunately another’s worry. I have these problems at home in my own daily practice when time is not of an essence. This is why it has been necessary to attempt to understand the specified racetrack scenario.

I will attempt to suggest how the condition of voids within the horn structure described in part one lead to abraded feet. It is actually a simple matter where the voids represent a wall detachment/lock up cavitation, which when the affected wall area reaches the level of bearing is imperfectly attached so as to have a loss of integrity with the underlying and surrounding horny tissue. The remaining wall structure gradually and simply fractures away from a defective basal connection and then further disintegrates under the loading associated with the stresses of athletic performance and when any attempt is made to nail into it.

There is a complicating factor in feet containing dry seroma cavities which I will attempt to explain. The integrity of feet which are affected in this way remain fine, and SEEM to remain thus until the separated area grows down to a level of the white zone junction, when the farrier’s nails penetrate into the cavity in order to attach a racing plate. The action of nail penetration seems to trigger a secondary effect, an influx of bacteria and yeast infection, associated with loose wall, seedy toe and/or white line disease kick-off, all of which assist the weakening conditions related to shoe loss and separation of the hoof wall from its junction with the solar plate. The author feels infection in itself is an induced condition and secondary to the original insult. The breakdown of the wall sole junction is without doubt related to environment and compaction by the racing/training surfaces.

To identify the onset of the syndrome takes very close observation as the initial indication is masked by the covering racing shoe and is not unusually seen as an extremely thin linier fissure, on many occasions detected by little more that a gut feeling. Having said this, if the fissure is missed at a very early stage, during the course of a full shoeing cycle great horn destruction in the area of the white zone will take place. A seedy toe, yeast-induced wall separation will happen and will unless effectively dealt with, migrate up the bi-sulphide junction more quickly than the wall can grow downwards, creating a chronic and accelerating condition. This horn decay is fortunately something that can be today easily controlled and/or reversed with recently and specifically developed products which condition hoof horn and destroy hoof related infection. I have trialled a conditioning gel product over the past two years with fantastic results.

There is when addressing problem feet today a distinct move towards the early use of hoof rebuilding materials and the attachment of alloy plates with glue products, from my viewpoint somewhat of a cop out and the equivalent of a band-aid exercise, undoubtedly. “Glue destroys the integrity of viable and healthy hoof horn.” This rebuild/attachment method is a nightmare to the racecourse farrier as these rebuilt feet and shoes attached with glue seem to be easily rejected. During the course of a year several reinforced feet / glue-on shoes are lost at the racecourse prior to racing; in fact it is fair to say the majority of front feet presented have evidence of glue/rebuild materials present. The shoes seem predisposed to falling off for many reasons. When this happens most of the lower hoof wall falls away with the polymer and /or acrylic. There is never sufficient time for the racecourse farrier to re-glue or rebuild a foot so the retained farrier has to find a way to replace the glue-reinforced/attached shoe using the traditional nailing method. There is no crisis more critical than getting a horse to the starting gate sound once it is at the racecourse premises. It is a very stressful time for everybody involved, and damaged feet are conditions best avoided wherever it is preventable.

So how can feet be made to regenerate sufficiently after having been subjected to treatment with re-enforcing material? The basic conclusion seems to be getting back to common sense methods, good diet, working on suitable surfaces (sea sand is not one of these), good husbandry, a regular shoeing cycle, sufficient hygiene, suitable bedding, pre-racing foot conditioning and the essential observant farrier. I feel a most important aspect is conditioning of the animal and its limbs in a way to assist sufficient horn keratinisation, which possibly is effected by training on suitable surfaces.

Steeplechase horses subjected to an element of road work in their preparation seem to have less hoof problems, yet this may simply be that they do not race on very firm ground, a seasonal influence. For the future, should we consider fitting a rolled toe shoe when animals are going to be asked the perform on really hard ground? There seems to be no place for the square toe being used on racehorse due to a lack of traction during the acceleration phases, but a very light roll, who knows? We will, in the next couple years no doubt! I feel there will be a niche for the rolled toe during the recovery stage from this condition but as a preventative measure? As a training aid? I will undertake such a study now that it has been suggested.

Current research on Pelvic Asymmetry in Racehorses

Steeplechase racing in particular is a high risk sport for the horse. There is currently some fairly extensive research into racehorse injuries and fatalities on the racecourse, with previously published scientific reports on the subject being widely available. The racing industry is aware of the need for such reports, as the industry itself is very much in the public eye with regard to injury rates on the racecourse. Lameness is one of the main reasons for wastage in the racehorse industry, and was the reported cause of 68% of total horse days lost to training in a study of racehorses in England (Rossdale et al. 1985).

This study also suggested that 10% of all diagnosed lameness cases were caused by tendon injury. Overstrain injuries to the superficial digital flexor tendon (SDFT) are amongst the most common injuries observed in the athletic horse (Goodship, 1993). It is therefore important to determine all possible causative factors of SDFT injury so that methods for preventing injury can be implemented as part of a training programme.

HINDQUARTER ASYMMETRY

The hindquarters of the horse provide the propulsion, and the forelimbs support 60% of the horse’s weight. Problems affecting the pelvic structure in the horse can lead not only to poor performance, but also to an unlevel gait and to lameness of the hindlimb. There are to date very few scientific reports on the frequency of hindquarter asymmetries in the horse, although Bathe (2002) found that most hard working horses were likely to have some degree of pelvic asymmetry.

This factor may not always affect performance, as many successful horses have been found to have asymmetry of the pelvis. Dalin et al. (1985) investigated the hindquarter asymmetry in Standardbred Trotters for any correlation with poor performance. He measured differences in height between the left and right tuber sacrale when the horse was standing square. Of the 500 horses measured 39 of them showed marked hindquarter asymmetry. In 30 horses the tuber sacrale was lower on the left, and in 9 horses it was lower on the right. The asymmetric horses had significantly inferior performance (measured by total earnings) compared to the symmetrical horses.

All the horses were trained and raced in Sweden on a left handed track. The asymmetrical horses were also of significantly larger body size than the symmetrical horses. In a recent study undertaken by Stubbs et al. (2006) in conjunction with the Hong Kong Jockey Club, a number of racehorses were presented for euthanasia (for injury and/or lameness). Racing and training details were examined in detail, and a clinical examination was carried out before the horses were euthanased. Following post mortem the thoracolumbar spine and pelvis were dissected out and examined. Although not part of the study it was noted that asymmetry of the pelvis was prevalent in many of the horses that had been dissected, the reason probably being due to a natural torsion of the pelvis as a result of training and racing on right handed tracks only.

It is suggested that asymmetrical loads on the pelvic structure caused by external factors (such as racetrack), and by internal factors (such as locomotor apparatus pain) may lead to a higher stress being placed on one hindlimb, and as a result lead to the development of pelvic asymmetry which may be apparent as pelvic rotation. Improper movement patterns of the hindquarters, due to pain caused by overuse or from fatigue, may also result in abnormal alignment of the pelvic structure.

This in turn may then cause overloading on the forelimbs (by off loading the hindquarters) and therefore predisposing the forelimbs to injury. If this can be proved then surely this would emphasise the importance of correcting pelvic misalignments using manipulation techniques such as chiropractic, osteopathic and myofascial release approaches. There is some unpublished material available to support the use of McTimoney manipulation methods and other soft tissue manipulation in the correction of pelvic rotation. Hindquarter asymmetry is often associated with sacroiliac joint lesions or with chronic hindlimb lameness.

The tuber sacrale can appear asymmetrical in clinically normal horses as well as in horses with misalignment of the sacroiliac joint (Dyson, 2004). Horses with longstanding poor performance attributed to chronic sacroiliac damage were investigated by Jeffcott et al. (1985). The majority of these horses showed some asymmetry of the hindquarters with the tuber coxae and tuber sacrale lower on the same side that the animal was lame on. Hindquarter asymmetry may be due to some tilting or rotation of the pelvis in addition to muscle wastage of one quarter, usually the side the horse is lame on.

ABNORMAL ALIGNMENT OF THE PELVIS

Pelvic rotation or abnormal alignment of the pelvis to the thoracolumbar spine can be measured by the level of the tuber coxae to the ground. If the horse is unable to produce the propulsion from its hindquarters due to discomfort in the pelvic region, then the forelimbs may be required to provide more horizontal propulsion. The horse will in effect be pulling himself forward with his forelimbs, rather than pushing from his hindquarters. This may result in over development of the shoulder muscles, thereby reducing the efficiency of the forelimb movement by adding unnecessary weight. Unpublished data has suggested a positive relationship between injury to the forelimb stay apparatus and pelvic asymmetry, particularly where the presence of functional asymmetry in the hindquarters was found to be due to pelvic rotation, and not as a result of differences in individual bone lengths of the hindlimb.

LAMENESS AND COMPENSATORY MOVEMENT PATTERNS

The compensatory mechanisms of horses with lameness have been extensively researched and reported. The potential for secondary injuries resulting from a horse’s attempt to compensate for lameness by altering its gait pattern are still unclear. Clayton (2001) found that when a lame limb is supporting body weight, the horse minimises pain by decreasing the load on that limb, resulting in a compensatory increase in the vertical forces in other limbs. The compensating limbs are therefore subjected to abnormally high forces, and these may lead to lameness in the compensating limbs. Uhlir et al. (1997) found that in all cases of diagnosed hindlimb lameness that true lameness of the left hind caused a compensatory lameness of the left fore, and that true stance phase lameness of the left fore caused a compensatory lameness in the right hind. TENDON INJURY The SDFT is the most frequently injured tendon in horses. In a recent study of steeplechase horses diagnosed with tendon and ligament injuries sustained during training, 89% occurred in the SDFT (Ely et al. 2005). It has been suggested that an optimum level of exercise is required at an early age for tendon adaptation to training, but with increasing age accumulation of microdamage and localised fatigue, failure to the tendon will occur with increasing exercise (Smith et al. 1999). The induction of injury to the SDFT occurs when loading overcomes the resistive strength of the tendon. Factors which increase the peak loading of the SDFT, such as weight of rider, ground surface, shoeing, conformation, incoordination, jumping, and speed will act not only to increase the rate of degeneration, but will also increase the risk of the onset of SDFT strain (Smith, 2006). Therefore the prevention of tendon strain-induced injuries by reducing some of the risk factors that increase loading on the tendon may provide the most satisfactory answer.

ANIMAL MANIPULATION TECHNIQUES

McTimoney Animal Manipulation aims to improve asymmetries through manipulation. There has been much anecdotal evidence for the benefits of McTimoney Manipulation Techniques on animals (Andrews and Courtney, 1999). There is anecdotal evidence to suggest that McTimoney and other manipulative therapies can make a difference where veterinary medication has failed (Green, 2006), although the application of manipulation techniques in veterinary medicine may be dependent of further research into the clinical effects of manipulation. Manipulation techniques are thought to cause muscle relaxation and to correct abnormal motor patterns which may be the result of muscular imbalances and restricted joint motion or altered joint mobility (Haussler, 1999). There is some unpublished material to support that there are significant changes in the symmetry of the pelvis after the application of McTimoney manipulation techniques, and that there is continued improvement one month after initial treatment.

CURRENT RESEARCH INTO PELVIC ALIGNMENT

In a recent unpublished study a group of 40 steeplechase horses in training, all using the same gallop, were measured for pelvic asymmetry. The measurement technique used was a somewhat simple (but reliable) method. Each horse was measured on flat, level concrete while standing completely square and weight bearing on all four limbs. Measurements were taken vertically using a horse measuring stick with a spirit level, from the most dorsal aspect of the lateral wing on the ilium (the tuber coxae) to the ground, on the left and right sides. Various data was collected on each horse, regarding race history, how many races run, whether “bumper” (flat races for steeplechase bred horses), hurdle or steeplechase, prize money earnings, handicap rating, and also brief veterinary history. The aim of the study was to compare pelvic rotation in 20 sound horses to the incidence and degree of pelvic rotation in a group of 20 horses with SDFT strain in either one or both forelimbs. Both the sound horses and the injured horses were in training with the same trainer, and therefore had used the same gallops, and underwent the same training regime. Although no significant difference was found in the number of horses with pelvic rotation in sound horses compared with the number of horses with tendon strain, there was a high incidence of pelvic rotation in the group as a whole, with a predominance towards pelvic rotation on the right.

This could have been due to training methods or gallops used, and certainly warrants further research. There was no significant association between side of pelvic rotation and side of forelimb tendon strain, but again warrants further investigation using a larger number of horses. Due to the prevalence of right side pelvic rotation it would not have been possible to show any significant associations anyway between left and right forelimb injury. The study did present some trends for age of horse, sex, and race history; showing that the number of horses with pelvic rotation and tendon injury increased with age. Geldings tended towards a higher incidence of tendon injury, and mares tended towards a higher incidence of pelvic rotation. There were equal numbers of sound and injured horses for each race type, but the degree of pelvic rotation in horses that had fallen was notably larger than in the horses that had not fallen.

FUTURE STUDIES INTO PELVIC ASYMMETRY

The preliminary investigation as described above has formed the basis for further research into abnormal pelvic alignment in racehorses, and whether or not there is any association between side of misalignment and side of forelimb injury. Further research is due to be carried out with a larger sample of horses, and from different yards, to investigate whether there is any prevalence as to the side of misalignment, or if pelvic alignment is affected by training methods and the use of different gallops.

The Equine Heart - Anatomy, Function and Performance

Exciting new advances in ultrasound image technology have provided a better understanding of both the anatomy and function of the heart at rest and during exercise. In the last 30 years many veterinary clinics and universities with equine departments that study equine physiology are able to study the heart of the equine athlete in their own sports performance laboratories, while exercising on a high-speed treadmill. Considering that heart rate is one of the most frequently measured physiological variables in exercise tests, Thoroughbred racehorse trainers have largely failed to take advantage of the heart rate monitor as standard equipment. However, heart rate monitors are commonplace in eventing and sport horses. Understanding the heart’s function, and its response and adaptation to training, can provide trainers with a competitive edge.

ANATOMY AND FUNCTION

The heart of a Thoroughbred weighs about 1% of the horse’s bodyweight but can be as high as 1.3-1.4% in elite animals. Therefore an average 1000 pound horse has a heart weighing between 8-10 pounds. The horse has a proportionately larger heart per unit of body mass as compared to other mammals. The horse’s heart rate is 20-30 beats per minute at rest and may have a maximal heart rate of 240 beats per minute during maximal exercise. The fact that the horse is able to increase heart rate by nearly 10 times the resting heart rate is a contributing factor to their athletic superiority. As in all mammals, the heart consists of four chambers with valves that open and close as the heart muscle relaxes and contracts to insure blood flows in the right direction. The two pumping chambers are the left and right ventricles, and the two receiving chambers are the left and right atria. The left ventricle is larger than the right ventricle.

Specialized cells within the heart conduct electrical activity that coordinates the muscles of the heart to contract in order to optimize blood pumping. Electrical impulses of both the atria and ventricles are isolated by a fibrous ring; preventing them from contracting simultaneously. The only point at which electrical activity can pass between the atria and the ventricles is via the Purkinje fibers found in the wall between the left and right ventricle. When the atria contract, blood is delivered to the larger volume ventricle that lies beneath. The right side of the heart receives unoxygenated blood from the body and pumps it to the lungs to allow the red blood cells to uptake oxygen. Oxygenated blood returns to the left side of the heart, and the left ventricle pumps it out the aorta to the rest of the body. The cardiac cycle consists of a contraction/ejection phase (systole), and a relaxation/filling phase (diastole). Stroke volume (SV) is the volume of blood pumped in each beat, and is influenced by the muscular contraction of the ventricles, their resistance to flow during systolic ejection, and their ability to fill during the diastolic relaxation. The structural integrity of various anatomic components of the heart such as the valves and septa between the chambers affect heart function. Stroke volume in a 500 kg Thoroughbred is approximately 1.3 litres and can increase by 20-50% during exercise. Cardiac output (CO) is stroke volume (SV) multiplied by heart rate (HR); therefore CO = SV x HR. At rest the cardiac output is approximately 6.6 (25 litres) gallons per minute and increases to an amazing 79 (300 litres) gallons per minute in elite athletes during exercise. A horse’s total blood volume is approximately 10 gallons, representing 10% of its body weight.

At rest 35% of the horse’s blood volume is red blood cells, however they can amazingly increase their red blood cell count on demand to 65% of their blood volume during a race, with up to 50% of the total red blood cells stored in the spleen. The horse has a proportionally larger spleen per unit of body mass as compared to other mammals. The red blood cells are void of a nucleus and have the large protein haemoglobin that transports oxygen. The horse’s heart is able to handle the increased viscosity of the blood. During exercise blood is diverted away from internal organs such as the intestines and kidney to working muscles used in motion.

THE HEART AND VO2 MAX

The heart is a major determinant in VO2 max, a measure of aerobic capacity. VO2 max is the maximal rate of oxygen consumption that can be consumed by the horse. VO2 max is determined by cardiac output (stroke volume x heart rate), lung capacity, and the ability of muscle cells to extract oxygen from the blood. During exercise the oxygen requirement by muscles can increase to 35 times their resting rate. Sydney University studies have shown that training can increase a Thoroughbred’s VO2 max by 20% or more, with this improvement highly attributable to the heart’s pumping capacity. VO2 max expressed as millilitres of O2 per kilogram of bodyweight per minute (or second). At rest the horse absorbs 3 millilitres of oxygen per kilogram of body weight per minute. Maximal rates of oxygen intake vary within breeds and training state, but fit Thoroughbreds have a VO2 max of 160-170 ml./min./kg and elite horses can achieve 200 ml./min./kg. By comparison elite human athletes have a VO2 max of about half or 85 ml./min./kg. Pronghorn antelopes have a VO2 max of 210-310 ml./min./kg. VO2 max is a high indicator of athletic potential, and has been found to be highly correlated with race times in Thoroughbred horses. A horse with a higher VO2 max had faster times (Harkening et al, 1993). The ability of the horse’s muscle mass to consume oxygen far exceeds the ability of the heart and lungs to provide oxygenated blood. Therefore cardiac output is a limiting factor in performance. Conditions that improve cardiac output positively impact VO2 max.

HEART RESPONSE TO TRAINING

The heart has two initial responses to exercise, a rise in blood volume pumped and dilation of the blood vessels. The heart rate increases, and beats stronger. The stroke volume may increase from 20-50% above resting rates. Through training the heart becomes more efficient at delivering oxygenated blood to exercising muscles. Heart mass has been shown to increase with training. This hypertrophy (enlargement) in the heart comes in two ways, a thickening of the heart walls, and an increase in the size of the chambers, especially the left ventricle. Although the effects of training on the heart are not clearly understood, heart mass has been shown to increase up to 33% in 2-year old horses after only 18 weeks of conventional race training (Young, 1999). The increase in heart size results in increased cardiac output. Stroke volume has been shown to increase by 10% in as little as 10 weeks of training (Thomas et al, 1983).

Although not yet proved, it is likely that in addition to the strengthening, improved filling capacity of the pumping chambers when the heart is relaxed may contribute to the increases shown in stroke volume. Interestingly, maximal heart rate does not increase with training, and resting heart rates (unlike humans) do not decrease with training. Training can improve VO2 max from 10-20% in the first 6-8 weeks of training, after which further improvement is limited. The relationship between VO2 max and velocity is highly correlated, but the differences found in speed and performance of two Thoroughbreds with equal VO2 max can be explained by differences in biomechanics and economy of locomotion. Although the heart plays an important role in determining several physiological factors related to performance, it is merely one variable in the whole physiological equation that describes the equine athlete. Not only does the heart change and adapt with the rigors of training, but a myriad number of adaptations take place in the muscle fibers at the cellular level. As a result of training, oxidative enzymes in the muscles increase, along with the size and density of mitochondria, the powerhouse of the cell. Enhanced oxidative capacity results in increased utilization of fat and less reliance on blood glucose and muscle glycogen, being an advantage at both submaximal and maximal exercise, because fat is a more efficient energy fuel. An improved network in the number and density of capillaries provides more efficient blood flow and transit time to working muscles, which also become more efficient in buffering lactate in anaerobic exercise. Muscle, bone, tendons and ligaments modify their structure with the stresses of training. Depending on the event, the horse develops “metabolic specificity” and neuromuscular coordination for his chosen discipline.

EVALUATING THE HEART - ULTRASOUNDS

When evaluating the equine heart, ultrasound has become an extremely valuable non-invasive tool, revolutionizing equine cardiology. The heart’s anatomical structure and physiology can be readily determined as well as measurements in heart size, wall thickness, and identifying defective cardiac valve function. Findings can determine pathology of the heart and the cause of poor performance. The ultrasound examination of the heart (echocardiogram) is now considered an integral part of cardiovascular evaluation of equine athletes. An ultrasound machine works by emitting a beam of high frequency sound waves (>20,000 Hz) from an ultrasound transducer into the body tissues. In general, the waves can penetrate to a maximum of 15 inches (40 cm) and they interact with various tissue types in different ways. The waves can be scattered, refracted or attenuated. The reflected waves are transmitted back to the ultrasound transducer. This information is interpreted by the ultrasound machine which produces a two-dimensional black and white image called a sonogram. The frequency of the ultrasound waves emitted by the transducer markedly influences the quality of the image, depending on the depth of the tissues. Higher frequency ultrasound waves have a shorter wavelength and yield better resolution of small structures close to the skin surface. However, more energy is absorbed and scattered with high frequency, therefore high frequency transducers have less penetrating ability.

Conversely, a lower frequency transducer will have greater depth of penetration but poor resolution. The transducer selected for echocardiography should be the highest frequency available that will penetrate to the depths needed to image the heart in its entirety. Frequencies generally used for veterinary echocardiography range from 2.25-3.5 Mhz for adult horses. The three main types of ultrasounds available to veterinarians and researchers are the M-Mode, Two-Dimensional (2-D), and Doppler. Although M-Mode yields only a one-dimensional (“ice pick”) view of the cardiac structures, it can yield cleaner images of cardiac borders, allowing the researcher to obtain very accurate measurements of cardiac dimensions and critically evaluate cardiac motion over time. Two-dimensional echocardiography allows a plane of tissue, with depth and width, to be imaged in real time. This makes it easier to appreciate the anatomic relationships between various structures. 2-D echocardiography makes available an infinite number of imaging planes of the heart. Doppler echocardiography records blood flow within the cardiovascular system when blood moving toward or away from the transducer causes a Doppler shift. From this shift, it is possible to calculate the velocity of the moving blood.

ELECTRO-CARDIOGRAM (ECG)

An ECG (electrocardiogram) is another tool commonly used in evaluating the heart. It measures the heart’s electrical conductivity can identify a part that is not contracting properly. It is the tool of choice for diagnosing arrhythmias. The ECG provides information to the researcher about the quality and rhythm of the heartbeat. The appearance of the ECG changes dramatically from rest to exercise. Cardiac contractions are the result of a well-orchestrated electrical phenomenon called depolarization. In the myocardium are specialized fibers that are very conductive and allow rapid transmission of electrical impulses across the muscle, telling them to contract. There is uniformity in the sequence and force of both the filling and ejecting chambers, relying on a single impulse initiated by the sinoatrial (S/A or sinus) node. Another node is the A/V node (atrioventricular node) situated between the two chambers. The ECG measures electrical activity from the P-Wave, QRS, and T-Wave.

The P-Wave represents the electrical impulse measured across the atria, whereas the T-Wave measures the repolarization of the ventricles. The QRS represents the electrical impulse as it travels across the ventricles. Measurements between these impulses include the PR and ST segments and the PR and OT intervals, all of which can reveal abnormal heart function. Electrodes are placed in strategic positions on the skin surface to pick up the heart’s electrical activity. In clinical practice, 12 leads may be used in a diagnostic ECG, but usually there are three standard leads, I, II and III, placed at different areas around the ribcage and chest. Placement of the electrodes are critical, and can change the size and shape of the ECG. HEART MURMURS AN ARRHYTHMIAS Vascular diseases in horses, such as atherosclerosis, which contributes to strokes and heart attacks, are rare. Two of the most common heart abnormalities are heart murmurs and arrhythmias. A heart murmur is the sound of turbulent blood flow, usually caused by an abrupt increase in flow velocity. This turbulence is caused by increased velocity due to a leak or obstruction in one of the heart valves or because of abnormal communication between different parts of the heart. Heart murmurs, which are fairly common, occur in horses of all ages. They are called “innocent” when they are soft, short and variable without any other cardiac pathology. One study detected cardiac murmurs in 81% of 846 Thoroughbred racehorses (Kriz, Hodgson, and Rose 2000). Congenital heart defects are abnormalities that are present at birth, the most common being ventricular septal defect (VSD) where a hole is found between the two ventricles.

Oxygen-rich blood from the higher pressure left ventricle passes through to the lower pressure right ventricle and pulmonary artery during ventricular systole. Because some blood bypasses the lungs, it is not fully oxygenated and will have an adverse effect on cardiac function. Depending on the size of the hole, the horse may be fully capable of moderate activities without fatigue or shortness of breath. VSD is usually detected on the right side of the chest over the cranial part of the heart, and can be fully diagnosed with 2-D ultrasound and Doppler echocardiography. Atrial fibrillation is an electrical disorder of the heart rhythm, also know as an arrhythmia. Associated with diminished performance, the normally regular, organized atrial waves become irregular, disorganized and chaotic, and the atria fail to contract normally, leading to an unpredictable and irregular heartbeat. Accurate diagnosis using an electrocardiogram can determine type and severity, and often an oral or injectable drug such as quinidine can be administered to establish a normal rhythm. An arrhythmia can sometimes be caused by myocarditis, where part of the heart muscle tissue has died due to an infectious disease such as strangles, influenza or an internal abscess. Toxic damage to the heart muscle may occur from a severe deficiency of vitamin E or selenium. The most commonly recognized acquired structural heart disorders are degenerative valvular deformities. These defects, involving a thickening and deformity of the valve leaflets, cause inefficiency of one or more heart valves, resulting in dilation of the chambers trying to handle the regurgitated blood on either side of the damaged valve. If the leak is severe enough, the pressure in the veins leading to the affected side of the heart increases until fluid accumulation (edema) occurs.

HEART SIZE AND PERFORMANCE

For centuries, owners, breeders and trainers have been captivated by the idea that the horse’s heart may be the proverbial “Holy Grail” to understanding athletic performance, and predicting the future elite racehorse. The large hearts found in elite human athletes are well-documented. In the 1920’s the “Flying Finn” Paavo Nurmi, who won 12 Olympic medals in track including 9 Golds and set world records from 1500 meters to 20 kilometers, had a heart three times larger than normal (Costill). At postmortem, the legendary 7-time Boston Marathon winner Clarence De Mar was shown to have an enlarged heart and massive coronary arteries (Costill). In 1989, it was believed that Secretariat, American Triple Crown winner of 1973, had a heart weighing over 10 kg (22 lbs.), and may have had a VO2 max of 240 ml./kg./min. Autopsies showed that the great Australian racehorse Phar Lap had a heart weighing 6.4 kg. (14.1 lbs), 20% larger than normal, and Key to the Mint, American champion 3-year old of 1972 and excellent broodmare sire, had a heart weighing 7.2 kg (15.8 lbs). Secretariat’s rival and runner-up Sham had one of the heaviest hearts recorded, weighing in at 18 lbs. (8.2 kg). Some of the first studies that scientifically attempted to correlate heart size with race performance were conducted in the 1950’s and early 60’s.

The Heart Score concept was first discovered and developed by Dr. James D. Steel, a professor of veterinary medicine at the University of Sydney in Australia in 1953. Using ECG (electrocardiography) to studying herbivores, he began studying the occurrence of heart disease in racehorses. His examinations led him to the development of the “Heart Score” which was his term to describe the correlation between the QRS (intraventricular conduction time) complexes and the performances of several elite versus average racehorses at the time. He believed that the higher heart score number based on the QRS duration using the standard bipolar leads must be correlated with the larger heart size and weight found in superior racehorses. Steel developed a ranking system that placed male horses with a heart score of 120 or more (116 or more for fillies and mares) in the large heart category, between 103-120 in the medium to normal category, and 103 or less in the small heart category.

His conclusion was based on the assumption that the QRS represents the time required for the electric wave to spread and depolarize the ventricular mass. He believed that the QRS interval corresponds to the beginning and end of ventricular depolarization. As the ventricular muscle mass increases, a longer time will be necessary for the ventricular depolarization to take place. Therefore, he believed the higher the heart score the larger the heart mass (and size) Unfortunately, Steel was wrong! Steel’s conclusions seemed logical at a time when equine cardiology was in its infancy. But in the horse (and hoofed mammals) the depolarization process differs from that of small animals because of the very widespread distribution of the Purkinje network. These fibers extend throughout the myocardium and ventricular depolarization takes place from multiple sites. The electromotive forces therefore tend to cancel each other out; consequently, no wavefronts are formed, and the overall effect of the ventricular depolarization on the ECG is minimal. (Celia 1999) Today, we know that ECGs provide little or no information about the relative or absolute sizes of the ventricles.

An ECG cannot measure heart size and cannot be used to correlate its size and / or mass. In several studies, heart score showed a relationship neither with body weight nor with ventricular mass, as determined by echocardiograph. Heart score did not correlate with heart size and cannot be regarded as an index for predicting potential performance (Lightowler et al 2004). Although a study using Danish Standardbreds showed a correlation between heart score and Timeform ratings, using these scores to determine heart size has largely been disproved.

HEART SIZE AND PERFORMANCE

Current research in the field of equine exercise physiology continues to investigate the heart and cardiac output. The size of the heart is a key determinant of maximal stroke volume, cardiac output and therefore aerobic capacity, and several new studies have proved this relationship. A recent breakthrough study demonstrated a significant linear relationship between British Horseracing Board Official rating or Timeform rating and heart size measured by echocardiography in 200 horses engaged in National Hunt racing (over jumps) (Young and Wood, 2001). It is the first study that positively correlates heart size to performance. Additionally, a significant strong relationship has been found between left ventricular mass (and other measurements of cardiac size) and VO2 max in Thoroughbred racehorses exercising on a high-speed treadmill. (Young et al 2002). Interestingly, no such relationships have been reliably been found when horses employed in flat racing were examined, suggesting that, as might be expected, VO2 max and heart size are more important predictors of performance for equine athletes running longer distances. It must be emphasized that these research studies were conducted on older racehorses that were already racing and training, very different from an untrained yearling.

CONCLUSION

Understanding the equine heart and its role in equine physiology will remain of great interest to breeders, owners and trainers. Future use of heart rate monitors and heart evaluations using ultrasound technology to identify heart pathology and abnormality will undoubtedly contribute to future breakthroughs in training and racing. The equine heart still remains just one variable in the elusive equation that makes for a great racehorse.

Racing power - supporting muscular effort through nutrition

The powerhouse for a horse in training is found in its large muscle mass. Whilst genetic makeup within the Thoroughbred breed has a large impact on a horse’s innate racing ability, dietary factors will also influence subsequent performance. There are many elements found in a racehorse’s diet that will help to support muscle function. Hydrolysable carbohydrate (sugar and starch), assisted by fermentable fibre, will help to maintain important muscle stores of glycogen (a carbohydrate fuel).

Dietary electrolytes, which are integrally involved in muscle contraction, are essential to offset electrolyte loss in sweat. Key dietary antioxidants such as vitamins E and C and also antioxidant co-factors, such as copper, manganese, zinc and selenium, are also important as part of the body’s antioxidant team which strives to reduce the formation of free radicals or reactive oxygen species, and to limit their damaging effects on the body. Free radical damage has previously been implicated in the process of exercise induced muscle damage.

GLYCOGEN STORES MUST BE REPLENISHED FOLLOWING EXERCISE

One of the most important functions of the diet is to replenish the horse’s energy stores in muscle on an ongoing basis. A racing ration needs to support the synthesis of glycogen to maintain the store of this important fuel, which is used in increasing amounts during exercise. Glycogen, which consists of a large branched chain of glucose units, is stored in both skeletal muscle and the liver and it represents one of the largest potential energy stores in the body. Horses being natural athletes, have a relatively large muscle glycogen store when compared to other species. As the glycogen content of horse muscle is influenced by the proportion of different muscle fibre types present, this means that there is a genetic influence on the overall glycogen content. Fast twitch fibres (Type IIb), which are found in increased numbers in talented sprinting horses, store relatively more glycogen than the slower type I and type IIa fibres. However, both diet and training can influence the level of glycogen stored in muscle. Exercise training for example has been reported to increase muscle glycogen content by 30-60% in horses. Logically, diet should have a significant effect on the storage of muscle glycogen as it provides the building blocks for glycogen synthesis. Glycogen can be synthesised efficiently from dietary starch, which is another polymer of glucose found in cereals. Glycogen can also be produced from certain glycogenic amino acids, released from the protein content of feed. In addition, propionic acid, which is a significant volatile fatty acid produced in the horse’s hindgut during the fermentation process, can also ultimately be converted to muscle glycogen.

In terms of the day to day diet, starch is by far the most direct and most efficient precursor for glycogen and so it is therefore not surprising that cereals, which are high in starch, have been the mainstay of racing diets for many years. In recent years we have seen the introduction of racing feeds that are lower in starch and sugar than traditional racing rations, with a greater emphasis being placed on digestible fibre and oil as energy sources. Whilst there are many health benefits attributable to this type of diet, the effect of changing the level of starch in the diet on muscle glycogen should always be considered.

MUSCLE GLYCOGEN - AN IMPORTANT FUEL BUT NOT THE KEY FACTOR IN FATIGUE

Muscle glycogen is a major source of energy (ATP) to working muscle during intense exercise, which is characteristic of racing. The amount of muscle glycogen used during training or racing will depend on its rate of utilisation, which in turn is affected by the speed and duration of the exercise undertaken. In general terms, the higher the speed, the faster muscle glycogen is broken down and used.

The duration of fast exercise is normally curtailed, which limits the overall amount of glycogen used. During slower work, although the rate of glycogen utilisation is much lower, exercise can usually be continued for a much longer time allowing more glycogen to be utilised overall (see figure 1). Total muscle glycogen content can be reduced by about 30% during a single bout of maximal exercise in horses. However, as muscle is a mix of different fibre types, the depletion of glycogen in individual fibres may be greater than this depending on the pattern of fibre recruitment during the exercise. Studies, however, have shown that even the IIB muscle fibres, which use glycogen at the fastest rate, are not totally depleted of glycogen following racing.

This supports the notion that although glycogen is an important fuel source for racehorses, glycogen depletion is not the most important factor in fatigue. However, exercise studies do suggest that power output and exercise performance can be decreased in horses where muscle glycogen has failed to be adequately replaced following a previous race or piece of hard work. This was the conclusion drawn by Lacombe and co-workers (2001) who reported that horses with replete muscle glycogen stores were able to run for longer periods during a maximal exercise test compared to horses whose muscle glycogen level remained low following a previous exercise bout. Whilst there are always horses that will buck the trend, this research emphasises the need to allow a suitable period of time between races, but also between bouts of fast work and subsequent racing to allow muscle glycogen stores to be replenished.

In contrast to human athletes, muscle glycogen replenishment in horses is relatively slow. Following racing or a hard work, research suggests that muscle glycogen can take up to 72 hours to return to pre-exercise levels when a traditional high cereal racing ration is fed. Certainly research carried out in the past 3 years would suggest that a high glycemic racing ration would be better placed to support glycogen replenishment more quickly following racing or hard work. There are many factors that affect the glycemic response to feed, which in simple terms describes the relative rise in blood glucose following feeding.

The starch and sugar content of a feed, however, is one of the most significant factors affecting glycemic response. Feeds that are high in starch and sugar e.g. a high cereal-containing mix produce a greater glycemic response compared with feeds that are very low in starch and sugar e.g. a forage only ration. Rate of glycogen synthesis following a glycogen depleting exercise bout was significantly higher in horses fed a high glycemic diet compared to those fed a very low glycemic control diet (Lacombe et al 2004, Lacombe et al 2006). In addition, absolute glycogen concentration in muscle was significantly higher both 48 and 72 hours following exercise in the high glycemic group compared to the control horses and muscle glycogen concentration had returned to pre-exercise levels following 72 hours. The benefit of a high glycemic diet for glycogen repletion does, however, appear to be time dependent. Jose-Cunelleras (et al 2006) reported a minimal difference in glycogen repletion in the first 24 hours following a glycogen depleting exercise bout between horses that were fed a high glycemic feed compared with a group where feed was withheld for 8 hours and another group of horses where only hay was fed.

A recent study also concluded that the route of administration of carbohydrate given post-exercise significantly affects the rate of glycogen replenishment. Horses that were given an intravenous infusion of glucose following exercise exhibited significantly greater glycogen storage rates and glycogen concentration in the first 6 hours following exercise compared to horses fed a similar quantity of glucose orally. In fact, the repletion of glycogen in response to oral glucose was minimal over this time period compared to the unsupplemented control horses (Geor et al 2007). Whilst it is difficult to draw direct comparisons with feeding practices used in racing, it is worth appreciating the possible differences in the rate of glycogen repletion when very high glycemic feeds are fed compared to very low glycemic feeds. The reality in many training yards I would suspect lies somewhere between these two extremes.

LOW GLYCEMIC DIETS CAN OFFER RACEHORSES MANY BENEFITS

There are many health-related benefits to feeding a ration that is lower in starch and sugar. However, one should be mindful of muscle glycogen when considering horses that are consistently fed a low glycemic diet. Specifically horses may be fed this type of ration because they are behaviourally more manageable, or because a specific condition such as the muscular disease recurrent exertional rhabdomyolysis (tying up) (RER) is present. A low starch diet is actively encouraged for horses that suffer from RER. McKenzie (et al 2003) reported that plasma creatine kinase activity (CK), elevations of which can indicate muscle damage, was significantly reduced following exercise in RER horses fed a low starch high fat diet versus a high starch low fat diet. In addition, lower resting heart rates have also been reported in horses fed a low starch high fat diet compared to the reverse.

A lower resting heart rate may be beneficial especially in RER horses where it reflects a calmer horse as stress has been implicated as a trigger factor for the condition. The current thinking on feed for horses with RER continues to be a low starch and sugar diet supplemented with oil. It is also important that the diet is well balanced, especially with respect to calcium and phosphorus. Adequate electrolyte provision is equally important, as is the intake of antioxidants such as vitamin E and other related trace minerals such as selenium. Any potential individual limitation in mineral or electrolyte absorption and retention should be investigated further with veterinary assistance in order that individualised adjustments can be made to the diet.

A SUPPORTING ROLE FOR PROTEIN IN MUSCLE RECOVERY

Whilst we are all no doubt aware that the amino acids that make up protein are important for muscle development and repair, protein and its constituent amino acids have received very little attention in horses in terms of their potential to limit exercise induced muscle damage and aid muscle recovery. In human athletes, co-consumption of a protein and carbohydrate drink during and after exercise appears to limit exercise induced muscle damage, ultimately allowing faster recovery (Baty et al 2007; Saunders et al 2004). Recent introduction of ingredients containing partially hydrolysed protein may improve absorption of these amino acids and peptides possibly offering further benefit. Finally, some nutraceutical ingredients including carnitine and creatine have been hailed as being beneficial to muscle function and recovery in human athletes. Creatine, which has been studied in the horse, has failed to offer any great advantage, largely due to its poor absorption. Likewise, carnitine has been reported to improve muscle blood flow during exercise in humans, helping to reduce muscle damage. However, this aspect has not as yet been investigated in horses and previous dietary studies with carnitine were not unequivocal about the ability of oral carnitine to increase muscle carnitine content.

Nasal Strips - increasing performance, reducing EIPH

Nasal strips’ future in Thoroughbred racing seemed limitless in the fall of 1999. Just two weeks after longshot Burrito won a race at Keeneland wearing one, 29 of the 101 horses competing in the 1999 Breeders’ Cup at Gulfstream Park November 6th had the 4-by-6-inch strip affixed 1.5 inches above their nostrils. More importantly, three of the eight winners wore them, including Cat Thief, who captured the $4 million Classic at odds of 19-1 under Pat Day, who was sporting a human equivalent, himself. The image of both Cat Thief and Day posing in the winner’s circle with nasal strips was a powerful one. Cat Thief’s victory was the second that day for Hall of Fame trainer D. Wayne Lukas, who earlier saddled 32-1 longshot Cash Run to win the $1 million Breeder’s Cup Two-Year-Old Juvenile Fillies.

She, too, wore the non-invasive strip designed to reduce an exercising horse’s airway resistance and decrease exercise-induced, pulmonary hemorrhaging (EIPH). The nasal strips received enormous national publicity after the Breeders’ Cup. Wouldn’t almost everyone in North America emulate Lukas? Stan Bergstein, the executive vice-president of Harness Tracks of America and a columnist for the Daily Racing Form, postulated long ago that if a horse wearing a blue balloon tied to his tail won a race, you’d see dozens of horses with blue balloons tied to their tails in the paddock the next day. Lukas, however, preached caution regarding the role of nasal strips in Cash Run and Cat Thief’s surprise Breeders’ Cup victories.

Regardless, Lukas and trainer Bob Baffert spoke at a meeting of the California Horse Racing Board Medication Committee meeting, January 12th, 2000, in support of nasal strips. According to a CHRB press release, CHRB Commissioner Marie Moretti expressed hope that using the strips could lead to the decreased use of bleeder medication for some racehorses. That never happened, as Lukas proved prophetic. He saddled three horses in the 2000 Kentucky Derby, two with nasal strips, and none of them finished higher than 12th.

According to Equibase, between October 23rd, 1999, and April 24th, 2000, 8,402 Thoroughbreds wore the strip and 1,077 won, nearly 13 percent. Apparently that wasn’t high enough. Less and less trainers used them, though Lukas still does. By the end of 2000, there was a story on the Internet site www.suite101.com entitled “The Demise of Nasal Strips.” Published December 12th, 2000, the article began, “The rise and fall of nasal strips was short and sweet.” Noting that the Daily Racing Form had originally listed the nasal strip in past performance lines for all tracks and that by mid-June was only listing them at Hollywood Park, the story concluded, “As quick as they appeared in the spotlight, they vanished.” The obituary was more than a bit premature. Miesque’s Approval won the 2006 Breeders’ Cup Mile at Churchill Downs wearing a nasal strip for trainer Marty Wolfson, who uses them on all of his 30 horses. “I’ve been using them on all my horses for two years,” Wolfson said in mid-March. “I use them on myself. I run and they help me when I run. I breathe easier. The only time I couldn’t use one was when Pomeroy was in the 2006 Forego Handicap at Saratoga.” Pomeroy won that stakes. He was denied the nasal strip at Saratoga because the New York Racing Association mysteriously banned nasal strips, a day after the New York State Racing and Wagering Board approved them for both Thoroughbred and harness racing. Currently, New Jersey is the only other state which doesn’t allow them, while Pennsylvania allows them for Thoroughbreds but not for Standardbreds. According to nasal strip co-inventor and president of Flair Nasal Strips Jim Chiapetta, some 15,000 nasal strips are sold world-wide each year: 9,000 in the United States, 3,500 in Europe, 2,000 in Australia and New Zealand and 500 in Dubai. He said they were used mostly on horses in eventing, then on Thoroughbreds, Standardbreds and Quarter Horses. Should they be used more often? Are they a realistic alternative to the powerful diuretic Lasix, which is now used by roughly 95 percent of all

Thoroughbreds in the U.S., though the rest of the horse racing world bans Lasix and all other race-day medications? Lasix, which is used ostensibly to reduce EIPH, can improve a horse’s performance dramatically the first and/or second time it is used, if for no other reason that its diuretic properties. Horses can lose 10 to 20 pounds through urination after Lasix is injected. That alone improves most horses’ performance. Think about it. If there is an apprentice jockey with even a modicum of ability, trainers scramble for his services just to decrease the weight his horse is carrying by five pounds. The efficacy of nasal strips can be judged in comparison to Lasix or by itself. “Lasix and nasal strips work in very similar ways,” said David Marlin, a consultant who worked for the Animal Health Trust in Newmarket, England, and co-authored Equine Exercise

Physiology. “From scientific studies, they seem to be equally effective in reducing bleeding.” Breathe Right strips were invented in 1987 by Bruce Johnson, who suffered from allergies. By the early 1990’s, they were being used for colds, allergies, snoring and athletic performance. They work by reducing the partial collapse of the soft tissues of the nose when it is under pressure because of the vacuum caused by the lungs during exercise. The mechanical, spring device maintains optimum air flow. Humans have an option for breathing: nose or mouth. Horses do not. They breathe only through their nostrils. Could nasal strips benefit horses? That’s a question Jim Chiapetta and his partner Ed Blach decided to explore. They had become friends at the Littleton Large Animal Clinic in Littleton, Colorado. Chiapetta, 48, returned to his clinic in Shakopee, Minnesota, to finish law school at William Mitchell College of Law. Blach, a former veterinarian who is now an animal products consultant, called Chiapetta in 1996 to discuss a possible equine version of a nasal strip. “We talked to a bunch of people and they said it wouldn’t work for horses, but I told Ed I think it could,” Chiapetta said. “We went ahead and made some prototypes.” Then they consulted Monty Roberts, the horse whisperer. “Ed used to be Monty’s resident veterinarian,” Chiapetta explained. Roberts was interested enough to have them test the strip at a track at Roberts’ farm north of Santa Barbara in California. “We didn’t have the adhesive done right,” Chiapetta said. “The riders were coming back and saying, `This horse felt better, more relaxed.’ So we figured there was something there.” Having breakfast one morning with Roberts, Chiapetta and Bloch came up with a name. “I was thinking about flaring nostrils, then I was thinking about air, and we came up with the name Flair,” Chiapetta said. Next, they consulted with CNS, the Minnesota company which manufactured Breathe Right. “They agreed to license it if it showed it reduces bleeding,” Chiapetta said. “They funded a study at Kansas State University.” That study and a majority, but not all, of a handful of subsequent studies - all involving a standard small sample of horses - showed positive results from nasal strips. “The nasal strips seem to help,” Dr. Howard Erickson of Kansas State University, a co-author of one of the studies, said last February. “We’ve done studies here.

There have been studies in Kentucky, California and Florida. In most of the studies, it decreases the bleeding by 50 percent and it also decreases the airway resistance.” He believes that most horses would benefit from both, because he believes almost all horses suffer from EIPH: “I think it’s nearly 100 percent that have some degree of bleeding for the movement of fluid from the capillaries to the airway. For some, it may be negligible. Quarter Horses will respond the same way. Standardbreds, too. You see it in rodeo horses and barrel horses.” That sentiment is shared by David Marlin, who has worked with researchers at Kansas State. “The bottom line is that all horses will break blood vessels in a race,” he said. “It happens with camels; it happens with humans, it happens with greyhounds.” Marlin also believes that nasal strips may be a more preferable treatment than Lasix. “It’s less complicated and you can’t build up tolerance,” he said. “If you think about a diabetic who uses insulin, he develops tolerance and needs more of it.

Do horses develop tolerance of Lasix? Generally, when you use drugs repeatedly, there’s a chance of adaptation to it. The nasal strip is different because it’s a mechanical device.” Then why aren’t trainers around the world, and especially in the United States, using them? Ironically, Chiapetta believes that the success of Cash Run and Cat Thief in the 1999 Breeders’ Cup is a major reason why. “It was the worst possible thing that could have happened,” he said. “We were on the front page of the New York Times Sports Section, the Wall Street Journal and Sports Illustrated. I think horsemen said, `Hey, this will make us win.’ So they strapped them on. And when they didn’t win, they took them off.” Some, not all. “They’re expensive ($7.95 per strip),” Wolfson said. “Some people don’t want to spend the money, but I think it’s worth it.” Day, the retired Hall of Fame jockey, knew they worked on him. “I found them to be quite helpful when I was riding a number of races back to back,” he said. “It seemed that I was less fatigued because I believed I was getting much more air into my lungs. I would have thought that would be more helpful to horses than riders. Horses only breathe through their noses. They cannot or will not breathe through their mouths.

If you can open up the nasal passages, open the airways, you would think it would be beneficial to the horses.” At the Havemeyer Foundation Workshop investigating EIPH, March 9th-12th, 2006, in Vancouver, Canada, Dr. Frederick Derksen, of the Department of Large Animal Clinical Sciences at Michigan State University, spoke about the role of airways in EIPH. He said, “A series of studies demonstrated that the use of a nasal strip decreases the number of red cells in bronchoalveolar laverage fluid after exercise. In horses, the majority of inspiratory resistance to airflow is located in the upper airway. The nasal valge region, located just cranial to the nasoincisive notch is a high resistance region, not supported by bone or cartilage.

These characteristics make this region particularly susceptible to collapse during inhalation. Application of the nasal strip in this region prevents nasal collapse and decreases upper airway resistance during exercise. This in turn is expected to reduce negative alveolar pressure during inhalation and decrease transmural capillary pressures.” The nasal strips are certainly a hit in New Zealand, especially with harness horses. After reading about the use of nasal strips in the 1999 Breeders’ Cup, Brian McMath, a committee member of the New Zealand Standardbred Breeders Association, imported a few samples. After the strips were approved by Harness Racing New Zealand, several trainers began using them and many had success, including Jim and Susan Wakefield’s Glacier Bay, who won the $105,000 PGG Sales Series Final at Alexandria Park in April, 2000, for trainer Cran Daigety. Eventually, Thoroughbred trainers began using the strip, too.

By the end of 2004, more than 700 winners in both harness and Thoroughbred racing won wearing the strip. “I have a technology background in chemistry and engineering, and what convinced me the strips work was basic physics,” McMath said. “It’s all about windpipe pressures and how a simple mechanical device like the springs in the nasal strip can beneficially alter these pressures.” The reception in Europe, at least for Thoroughbreds, was decidedly cooler. In an April 11th, 2000, letter, Peter Webbon, the Chief Veterinary Adviser to the British Jockey Club, noted that the senior veterinary surgeons from the European Horserace Scientific Liaison Committee (Britain, France, Italy, Germany) considered the question of nasal strips and decided to recommend to their racing authorities that their use should be banned for the following reasons: 1 “Other `gadgets’, such as tongue ties, which are allowed, are intended to address a specific clinical entity. Nasal strips are seen by trainers as a non-specific way of improving performances. 2 “If they improve performance, they should be banned, in line with performance enhancing medication. 3 “If they are ineffective, they should be banned because they give the impression that we condone practices that are intended to improve performance. 4 The manufacturers claim that they reduce the frequency/severity of EIPH.

The EHSLC veterinarians felt very strongly, for the sake of the breed, that horses should run on their merits. What would be the effect on the Thoroughbred in the long term if a horse won the Derby, wearing a nasal strip,that without the strip was unable to win a selling race?” To this day, they are banned throughout Europe for racing but allowed for training. Two years ago, Chiapetta met with Webbon and his assistant in Newmarket. “He said, `It reduces fatigue, which improves performance,’” Chiapetta related. “I said, `If you shoe them, do they run better? If you feed them, do they run better? If you train them, do they perform better? Where do you draw the line?’” Event horses are allowed to use them throughout the world because they were approved by the International Federation for Equine Sports (FEI).

On June 26th, 2006, Horse & Hound wrote that nasal strips “are becoming commonplace on the noses of top event horses,” and noted that Andrew Hoy’s Moon Fleet won the Badminton, a premier cross-country event in England. “I started using them two years ago,” Andrew Hoy said. “I’d seen them being used on horses and humans, and discussed their use with a vet. I had used a human one myself when I had a cold, and it seemed to help. I now use them on my horses at top events to give them every opportunity.” The story said that another eventer, Francis Whittington, uses them on his “advanced” horse Spin Doctor. “I tried the human version and noted the difference,” he said. “I believe it makes it easier for him to breathe so he can last the distance.” That’s the whole point. “Some people may think that more oxygen makes them run faster,” co-inventor Blach said. “That’s not the case. Rather, horses perform at their optimum level for a longer time so they can do what they’re made to do over the long haul. Maybe it’s too simple. It’s based on very simple physics that if you maintain the size of an opening, you’re going to maximize what goes through it, in this case air.” Asked if nasal strips help horses, Blach said, “Absolutely.” Perhaps the most confounding question about nasal strips is that even the single negative clinical study about them said that they do not reduce EIPH, but offered no tangible downside to their usage. Asked if there is a downside, Marlin said, “I think, as far as anyone knows from a scientific point of view, there is no evidence that there is.” Referring to that study, Chiapetta said it showed that horses using them “certainly weren’t less healthier. I don’t think there’s any downside to it.” Dr. Ted Hill, the New York Racing Association steward for the Jockey Club, said on April 11th, “Our only downside was how to regulate it. If a horse comes to the paddock and it falls off, what do we do? Do we treat it as equipment? We can’t put it back on. The significant problem we had originally was it possibly being an aid to bleeders, and relaying that to the public. That came up in an international meeting at a round table in Tokyo last October. It did not receive wide acceptance because it has some efficacy.”

So Japan does not allow them. Australia allows them for Standardbreds, but not for thoroughbreds. Yet, nasal strips are allowed for Thoroughbreds in Dubai and Singapore, as well as New Zealand. “It’s probably been embraced more in other countries than here, but in Thoroughbred racing here, furosemide (Lasix) is so embedded,” Kansas State’s Erickson said. “Furosemide reduces weight. It certainly reduces bleeding. But maybe we have to look for something better.” Maybe something better has been out there for eight years.

Nutritional ergogenic aids for horses

No doubt we are all aware of the plethora of dietary supplements that are now available and that are promoted as offering clear and profound benefits to our horses’ health, general well being and performance. In the latter category are the so-called ergogenic aids. So what are they, and do they work? These are the questions that this article aims to address. It should be made clear however, that as nutritional ergogenic aids are quite often not normal constituents of the equine diet and that they function by affecting one or more of the body systems of the horse, then they are by definition prohibited under the rules and regulations of racing. Consequently, this article neither advocates or seeks to legitimise, the use of the supplements discussed specifically, nor the use of nutritional ergogenic aids generally during training or racing.

DEFINITION

Ergogenic is defined as ‘work producing’. An ergogenic aid is therefore some system, process, device or substance than can boost athletic performance in some fashion, such as speed, strength or stamina. Broadly speaking there are five categories of ergogenic aids: biomechanical, physiological, pharmaceutical, psychological, and nutritional.

From an athletic perspective ergogenic aids may - • enhance the biochemical and therefore physiological capacity of a particular body system leading to improved performance • alleviate the psychological constraints that can limit performance • accelerate recovery from training and competition This article will focus upon the use of nutritional supplements that are marketed or currently being researched for their efficacy in improving athletic performance in horses.

HOW DO THEY WORK?

In principle nutritional ergogenic aids can enhance exercise performance in horses in a variety ways, depending on the nature of the particular supplement. For example an ergogenic aid might - • Enhance the lean mass of a horse by reducing body fat content whilst maintaining muscle mass, leading to an improved power to weight ratio • Improve the ability to counter lactic acid production or accumulation - producing a slower fatigue process in muscle • Increase muscle mass - resulting in increased power or strength • Increase the transport of oxygen around the body • Improve the efficiency of utilisation of body fuels such as fat, glucose and glycogen • Increase the storage of fuels within the body • Enhance the storage and utilisation of high-energy phosphates used in the early stages of fast exercise

WHAT’S ON THE MARKET?

A vast array of supplements are promoted as being effective ergogenic aids to the training and racing of horses. The table to the right offers an overview of the global ergogenic aids ‘catalogue’ but is by no means intended to be an exhaustive list.

CREATINE

Many of us will have heard of creatine in the context of nutrition and sport. It has been the great success story, efficaciously and financially, within the sports nutrition sector from the 1990s to the present. In 2004, for example, gross revenue from creatine supplement sales to sports people within North America alone was estimated at $400 million. This success largely stems from the fact that, unusually, it is a supplement that works! Admittedly, its effectiveness varies across different sporting disciplines. It has proven especially beneficial in sporting activities of comparatively short duration, such as the athletic disciplines of sprinting and jumping, but also in sports that require very high levels of power production as in rowing, swimming and track-based cycling. Creatine accomplishes this performance enhancement, firstly by elevating the levels of high-energy phosphates, ATP (adenosine triphosphate) and PCr (phosphocreatine), stored in muscles. Secondly, creatine can enhance the effect of training; i.e. it boosts the responsiveness of the muscles to stimuli generated by training.

This is often observed as increased muscle mass that arises from elevated production of the major muscle protein myosin and from enhanced levels of localised growth factors. The benefits of creatine supplementation in training and competition have not passed the equine world by, and a number of products are marketed specifically for horses. Unfortunately however, despite the positive claims made for these equine products they are not supported by scientific evidence. Indeed the opposite is the case. Sewell and co-workers in the UK and Essen-Gustavssen’s group in Sweden have conducted three rigorous placebo-controlled studies in horses. No positive effects of creatine supplementation on performance were found when parameters including time-to-fatigue, high-energy phosphate depletion and lactic acid production were measured. The underlying cause for lack of efficacy in horses is due to poor absorption of creatine from the equine gut, leading to inadequate levels being attained in the muscles. Even if a strategy could be devised to deliver creatine effectively to the muscle, some researchers are of the opinion that there would still be no effect.

They form this view on the basis that in comparison with humans the horse is an elite athlete wherein the level of creatine in equine muscle is at or very near to the physiological upper limit. CARNITINE Carnitine is another well-known dietary supplement widely marketed as an ergogenic aid in human sports nutrition and within the equine industry.

The role of carnitine in exercise in humans and horses has been researched for almost 20 years. The biological actions of carnitine that make it central to exercise include: Directly: transport of fats into muscle mitochondria where they can be used aerobically (oxidised) to generate ATP Indirectly: increase aerobic utilisation of glucose to produce ATP Indirectly: reduce lactic acid production (acidosis) Some research does indicate a positive effect of carnitine supplementation on exercise performance in human athletes, however there are other studies that seem to indicate the opposite. Conflicting research results have also been found for horses. Studies carried out by Foster and Harris in Newmarket during the 1990s showed that dietary supplementation could increase carnitine levels circulating in the blood, but did not appear to affect the levels in the muscles. In 2002 Rivero and his fellow researchers at the University of Cordoba conducted a placebo-controlled study into the effect of carnitine supplementation in 2-year-old horses when used in conjunction with an intensive 5 week long training programme.

Improved muscle characteristics were seen in the carnitine-supplemented group of horses, including a 35% increase in the proportion of fast-contracting (type IIA) muscle fibres, a 40% increase in the number of capillaries supplying blood to the muscle and an 11% increase in the level of glycogen stored in the muscle. After a let down period of 10 weeks most of these improvements were reversed. It was concluded that carnitine supplementation enhanced the training effect on muscles and that this could improve performance. Despite the large number of studies conducted over the years the balance of evidence does not yet allow a consensus to be reached on whether carnitine improves performance in horses (and humans) or not.

Of course this does not rule out a beneficial effect, and Rivero’s study would seem to be encouraging. GAMMA-ORYZANOL Gamma-oryzanol is not as the name implies a single substance, but is a mixture of chemicals, mainly ferulic acid esters, derived from rice bran. It has been popularised as a potent anabolic agent, i.e. a substance that promotes muscle growth leading to increased strength and speed. Gamma-oryzanol has been employed in equine and human athletes in the belief that it elicits increased testosterone production and stimulation of growth hormone. To date there is no published research describing the effects of gamma-oryzanol on exercise performance in horses, so in an effort to judge its potential efficacy we have to draw upon comparative studies in humans and other animals. Efficacy for gamma-oryzanol is debatable, as it is poorly absorbed from the digestive tract. What is more when given to rats, contrary to popular belief, it is reported to actually suppress endogenous growth hormone and testosterone production. Research carried out in humans fed 0.5g per day of gamma-oryzanol showed no improvement in performance, nor indeed any change in the levels of testosterone, growth hormone, or other anabolic hormones even after 9 weeks of supplementation.

Thus in summary, no scientific evidence exists to support the anabolic effects ascribed to gamma-oryzanol. DIMETHYLGLYCINE (DMG) AND TRIMETHYLGLYCINE (TMG) Both DMG and its precursor TMG cannot be regarded as new supplements having been researched briefly in the late 1980s with a single research report being published. Rose and colleagues at the University of Sydney’s veterinary department looked into the potential benefit of DMG on heart and lung function, and lactic acid production in Thoroughbreds during exercise. In this placebo-controlled trial DMG was fed twice daily to a group of thoroughbred horses that underwent a standardised exercise test at varying intensities before and after supplementation with DMG or the placebo.

On completion of the trial it was concluded that DMG produced no measurable improvement in any of the parameters, and that it exerts no beneficial effects on heart and lung function or lactic acid production during exercise. Warren and co-workers following experimental evaluation of TMG as an ergogenic aid came to a similarly negative conclusion. ß - HYDROXY- ß METHYLBUTYRATE (HMB) HMB is one of the few ergogenic aids available for use in performance horses that is supported by at least some credible science. Significantly, research developing and validating the use of HMG in horses (and farm animals) was instigated and carried forward over a number of years at Iowa State University, USA, and the concept and methodology are protected by US patents. HMB is a metabolite of leucine, one of the so-called branched-chain amino acids (BCAAs), that are themselves often touted as ergogenic aids, although there is no convincing evidence to support such a claim. Research seems to indicate that HMB supplementation when employed in conjunction with an effective training regime can benefit equine performance in a number of ways: • Enhance muscle development and increase lean muscle mass and strength by reducing the proportion of energy needed for exercise that is derived from protein and increasing the proportion derived from fat. • Reduce muscle damage (catabolism) during and after exercise and accelerate muscle repair. Some research suggests that HMB is a structural constituent of muscle cells that is destroyed under the physiological stress of exercise. • Increase aerobic capacity (oxygen utilisation) in performance horses by increasing both haemoglobin and the proportion of red blood cells in the blood (haematocrit). When HMB use was evaluated in practice under real racing and training conditions it appeared to reduce muscle damage, and to improve oxygen use by the muscles and overall performance.

NEW DEVELOPMENTS RIBOSE

Ribose is a potential new dietary ergogenic aid that began to be studied in 2002. It is a sugar that is the central component of ATP. As ATP stores are depleted during intense exercise in horses, it was thought that supplementing the horses’ diet with ribose might lessen the loss of ATP during exercise and enhance its regeneration during recovery. Kavazis and his colleagues at the University of Florida conducted two placebo-controlled studies in Thoroughbreds. In these studies ribose was fed twice daily as a top dressing for two weeks to a group of trained horses. The data from these two studies was contradictory and thus no conclusions can be easily drawn. However, two studies in humans have shown no positive effect of ribose supplementation on exercise performance.The balance of available evidence therefore suggests that ribose provides no ergogenic benefit in performance horses.

BIOAVAILABLE STABILISED OXYGEN

An unusual ergogenic product has recently appeared that purports to be a bioavailable supplementary source of oxygen. In simple terms, it is water that is apparently treated by a sophisticated electrical process so that it becomes a super-saturated solution of oxygen. It’s described as containing about 20,000 times more oxygen than that found in average tap water. As yet, there appears to be no convincing scientific evidence for this type of product, and what is more the explanation of its action does not seem to be physiologically credible. It is suggested that this bioavailable oxygen is absorbed from the stomach and intestine into the blood stream, however these tissues have not evolved for this purpose unlike the lungs. Even if we assume that all the oxygen from e.g. (100 mL) was taken up into the blood, the added benefit would be very small; 100 mL is roughly equivalent to 20 litres of oxygen. In comparison, an average horse exercising at racing speeds breathes in more than 2000 litres of air (420 litres of oxygen) every minute and the muscles use 75 litres of oxygen over the same period. We should also remember that for a normal healthy horse the blood is 98% saturated with oxygen.

WHERE NEXT?

The future direction for nutritional ergogenic aids is extremely difficult to predict as any new developments are likely to mirror advances in our detailed understanding of the basic biochemical and physiological processes that underpin exercise performance. In the past, much of the impetus for equine research in this area developed from human sports nutrition and this is likely to continue in the future. A closing comment to put all of this information into context would be that whilst one should always seek a feasible mechanism of action and proof of efficacy for new products, small numbers of horses used in trials and difficulties in measuring ‘performance’ means that science will not always come up with the absolute answer.

Equine Exercise Physiology - understanding basic terminology and concepts

Anaerobic work is performed at heart rates above 150 BPM and involves explosive power such as short sprints, acceleration, and fast galloping. A Quarter Horse running 2 furlongs would be deriving energy 60% anaerobically and 40% aerobically. The primary anaerobic fuel source is glycogen without the presence of oxygen. Typically a horse can perform purely anaerobic work for a short duration.

MUSCLES AND STRUCTURE

Horses have 700 individual muscles, and in thoroughbreds, muscles make up as much as 55% of the horse’s total body mass. The skeletal muscle consists of bundles of long spindle shaped cells called muscle fibres that attach to bone by tendinous insertions. The blood vessels and nerves that nourish and control muscle function run in sheets of connective tissue that surround bundles of muscle fibres. Each nerve branch communicates with one muscle fibre at the motor end. The nerve and all muscle fibres that it supplies are together termed a motor unit. Each time that a nerve is stimulated all of the muscle fibres under its control will contract. One motor nerve will supply from 10-2000 muscle fibres. A muscle’s unique ability to contract is conferred by the highly organized parallel, overlapping arrangement of actin and myosin filaments. These repeating contractile units or sarcomers extend from one end of the cell to another in the form of a myofibril. Each muscle fibre is packed with myofibrils that are arranged in a register giving skeletal muscle a striated appearance under a microscope. Muscle contraction occurs when the overlapping actin and myocin filaments slide over each other, serving to shorten the length of the muscle cell from end to end and mechanically pulling the limb in the desired direction. The sliding of the filaments requires chemical energy in the form of ATP.

MUSCLE FIBRE TYPES

The horse has three basic muscle fibre types: Type 1, Type 2A, and Type 2B. These fibres have different contractile rates and metabolic energy characteristics. Type 1 fibres, also known as “slow twitch” or “red fibres” have high oxidative capacity and are resistant to fatigue in part related to their high density of mitochondria which can utilize fuels aerobically and have the highest oxidative capacity. Mitocondria are the small organelles in the muscle cells that convert fuels (fats and glycogen) into ATP. They have the highest lipid stores, highest densities of capillaries, and the lowest glycogen stores. They have the lowest glycolytic enzyme capacity of the three fibre types. Type 2A are the “intermediate fibres” in terms of both contractile speed and metabolic properties between Type 1 and Type 2B. These fibres are aerobic, but also use a combination of glycogen and fat for energy generation.

The thoroughbred has a high percentage of these “intermediate” fast twitch oxidative fibres that can produce speed and still utilize large amounts of oxygen and resist fatigue. Type 2B “fast twitch” fibres have the fastest contractile speed, the largest cross-sectional area, the highest glycogen stores and glycolic capacity. They are ideally suited to short fast bursts of power. They have a low aerobic capacity and tend to depend on anaerobic glycolysis for energy generation. Genetics determine muscle type and composition and is 95% inheritable in humans, and is thought to be highly inheritable in horses (Snow and Guy). In evaluating the fibre type distribution in a number of breeds of horses, heavy hunters had a very large proportion of Type 1 fibres, while Thoroughbreds and Quarter horses had few Type 1 fibres and a large number of the faster contracting 2A and 2B types.

The percentage of each fibre type that a particular breed has in its muscle depends on the type of performance for which the breed is selected. Thoroughbreds have the highest number of the highly aerobic 2A fibres, illustrating the importance of oxygen utilizing pathways in the thoroughbred racehorse. Researchers also found that thoroughbred stayers have a higher number of Type 1 fibres than either sprinters or middle distance horses. Unfortunately, within a breed, the spread in fibre type distribution is so small that fibre typing as a predictor of performance is probably of limited value.

Muscle strength, size and shape can be predictive of muscle fibre ratios. Although each muscle may have a fibre type mix, generally a higher percentage of the “fast twitch” (Type 2) fibres are found in the horse’s hindquarters providing power, whereas the “slow twitch” (Type 1) are found in the forelimbs providing stride, rhythm and a weight bearing role.

VO2 MAX

VO2 Max is a measure of aerobic capacity. VO2 Max is the maximal rate of oxygen consumption that can be consumed by the horse. VO2 Max is determined by cardiac output (stroke volume x heart rate), lung capacity, and the ability of muscle cells to extract oxygen from the blood. During exercise the oxygen requirement by muscles can increase to 35 times their resting rate. VO2 Max is a high indicator of athletic potential, and has been found to be highly correlated with race times in thoroughbred horses. A horse with a higher VO2 Max had faster times (Harkening et al, 1993). Training increased VO2 Max. (Evans and Rose, 1987) VO2 Max is determined by measuring oxygen during exercise as increasing speed and/or incline of a high-speed treadmill incrementally increases the workload. VO2 Max expressed as millilitres of O2 per kilogram of body weight per minute (or second). At rest a horse absorbs 3 millilitres of oxygen per kilogram of body weight per minute. Maximal rates of oxygen intake vary within breeds and vary with breed and training state, but fit thoroughbreds have a VO2 Max of 160-170 ml./min./kg. By comparison elite human athletes have a VO2 Max of about half or 80 ml./min./kg. Pronghorn Antelopes have a VO2 Max of 210-310 ml./min./kg. When VO2 Max is determined, the speed at which VO2 Max is achieved is also measured. Comparing two (2) individuals with the same VO2 Max, one individual will have a higher speed at which the VO2 Max is achieved. VO2 Max calculations enable researchers to evaluate the fitness of a horse and its ability to utilise oxygen for energy.

ANAEROBIC THRESHOLD

Anaerobic threshold (also know as lactate threshold) is the level of effort usually expressed as a percentage of VO2 Max at which the body produces more lactate than can be removed. Anaerobic work is performed at a heart rate approximately above150 BPM and at intensities above 70% VO2 Max. At lactate threshold the cardiovascular system can no longer provide adequate oxygen for all exercising muscle cells and lactic acid starts to accumulate in those muscle cells (and subsequently in the blood as well). Lactate threshold research has recently focused on blood lactate threshold (LT) as a reflection of an individual’s level of training. There are always certain cells within muscles that are relatively deficient in oxygen and are therefore producing lactic acid, but at levels small enough to be quickly metabolized by other cells that are operating on an aerobic level. At some point the balance between the production of lactic acid and its removal by body systems shifts towards accumulation. Lactate threshold is usually slightly below VO2 Max, and will improve with training. Horses with increased LT not only experience less physical deterioration in muscle cell performance but also use less glycogen for ATP production at any level of performance.

TRAINING RESPONSES

Through training physiological changes take place in most of the horse’s systems. Major training responses take place in the blood, heart, muscles, and cardiovascular, neuromuscular and skeletal systems. The first 2-4 months of training increases the total amount of blood volume, red cell count, and hemoglobin concentrations and creates a more efficient circulatory system. Increased blood plasma in the first weeks of training contributes to improved thermoregulation and sweating capacity. After training for 3-6 months, an improved network in the number and density of capillaries provide more efficient blood flow and transit time to working muscles. After 4-6 months of training a multitude of adaptations take place at the cellular level. Oxidative enzymes in the muscles increase along with the number, size and density of mitochondria in the muscle cells. The enhanced oxidative capacity results in increased utilization of fat and less reliance on blood glucose and muscle glycogen, being an advantage at both submaximal and maximal exercise, because fat is a more efficient energy fuel. Training regimens that include speed work, and increased acceleration at intensities close to VO2 Max will also result in the increase of glycolic enzymes needed for anaerobic energy production.

Training at these higher anaerobic levels will improve the buffering capacity in the muscle cells. Buffers are chemicals that limit lowering of pH when lactic acid accumulates. The clearing and removal of lactic acid and wastes also becomes more effective. Heart mass has been shown to increase with training. Hypertrophy (enlargement) in the heart physically comes in two ways, a thickening of the heart walls, and an increase in the size of the chambers, especially the left ventricle. Heart mass has been shown to increase up to 33% in 2 year old horses after only 18 weeks of conventional race training (Young, 1999). The increase in heart size results in increased cardiac output. Stroke volume has been shown to increase by 10% after as little as 10 weeks of training (Thomas et al, 1983). A study has also shown that heart size is also correlated with VO2 Max using an ECG (Young et al, 2002). VO2 Max increases from 10-20% in the first 6-8 weeks of training after which further improvement is limited. Although the relationship between VO2 Max and velocity is highly correlated, the differences found in the speed and performance of two thoroughbreds with equal VO2 Max values can be explained by differences in biomechanics, and economy of locomotion. Horses with a high VO2 Max and efficient gait will use less energy to attain the same speed.

As fitness progresses, the horse will be able to attain a higher speed before reaching VO2 Max. An example would be a lightly trained thoroughbred hitting VO2 Max at 25mph, but after beginning a training program, the same horse would eventually be able to go 30 mph before reaching the limit. Although improvements in VO2 Max and aerobic capacity occurs early in the training stages, it’s not until 4-6 months that improvements are seen in bone and ligaments. This physiological mismatch is often the cause of many bone and soft tissue injuries. At maximal exercise levels, such as a gallop, increases are seen in bone density and mass. Bone density, shape and internal composition are related to strength. Medium tissues such as tendons and ligaments become thicker and more elastic. The modeling response of bone is stimulated by fast work, fortunately only short durations are necessary (Firth et al, 1999). Training at the trot or canter results in minimal changes in bone mass and density. Therefore, the trainer must gradually add speed work into the training plan with the goal of developing bone density. The peak time of bone development occurs between 2 and 3 years of age, with 50% of their primary structure replaced by their 3 year old year.

The ability of bone to adapt decreases with age, with some researchers believing that bone becomes more brittle with age, and young horses actually remodel bone more quickly and easily, and are at less risk than horses started later (McIlwraith). This idea is further supported by other researchers that found that tendons grow and adapt to the stresses of training more successfully prior to their 2 year old year (Smith, Birch, Patterson, Kane et al, 1999). Contrary to common belief, most current research indicates that early training may not only enhance bone and tendon development, but reduce the incidence of injury during training and racing, prolonging racing careers.

PERFORMANCE MEASURES

For over 30 years high speed treadmills have revolutionized the study of equine exercise physiology. Today many veterinary clinics and universities with equine departments are able to study the equine athlete in their own sports performance laboratories. The treadmill can easily evaluate the athletic potential of an equine athlete by standardizing variables used in an exercise test. A high speed treadmill can answer various questions relating to speed, ventilation, heart rate, VO2 Max, blood lactate, substrate (fuel) use, gait analysis, and endoscopic examination of the upper airway. The high speed treadmill will run at speeds in excess of 35 miles per hour, can be inclined at a 3-3.5% grade to simulate ground resistance and a rider’s weight. Treadmills equipped with a respiration calorimeter are used to measure gas exchange. Using indirect calorimetry, a loose fitted, padded face mask is attached to a motorized pump that monitors and analyses air breathed in each breath. The suction created by the pump ensures that expired air is collected and not re-breathed by the horse. The research team can design an exercise test tailored for desired performance measures.

The test can be designed as an incremental test, where horses are asked to perform at ever increasing high speed until reaching maximal exertion, or a longer endurance test. During a standard exercise test fitness can be monitored using heart rate, with a heart rate monitor. Heart rate is one of the most frequently measured physiological variables measured in exercise tests. Measurements of blood lactate, glucose concentrations, free fatty acids and pack cell volume can be taken throughout the test not just before and after. Knowing the horse’s weight is necessary in order to make calculations, and the horse is weighed prior to testing. During the test the airflow rate is measured in litres / minute. Both Oxygen (o2) intake and exhaled carbon dioxide (CO2) is measured. These measurements provide information to calculate VO2 (volume of oxygen), VO2 Max (maximal oxygen intake), and VCO2 (volume of carbon dioxide).

VO2 Max provides information on aerobic capacity, and the speed at which VO2 Max is achieved. Being equipped with a heart rate monitor, the speed at which maximal heart rate achieved is also known. The relationship between running speed, heart rate and oxygen consumption is linear up to VO2 Max. Two commonly used variables that are used to describe the relationship between heart rate and velocity are V140 and V200. There is a high correlation between V200 (velocity at 200 beats per minute) and VO2 Max. These variables are simply used to describe speeds attained at different heart rates. Numerous graphs and charts can be generated to display a horse’s athletic progress over time. Similarly, the speed at which blood lactate reaches certain levels is also measured. Lactate levels at different speeds are used to measure anaerobic capacity. Onset of blood lactate accumulation (OBLA) is recorded as VLA4. This is the speed achieved when blood lactate concentrations reach 4 mmol./l. Elite thoroughbreds can tolerate lactate concentrations as high as 30 mmol/l. A sprint test on a thoroughbred may be run at supramaximal intensity of 115% VO2 max for a 2 minute period, near maximal heart rate, whereas an endurance horse such as an Arabian may be expected to run at 35-40% VO2 max for 90 minutes. Interestingly, Arabians have been found to use more fats as fuel than thoroughbreds (Kentucky Equine Research, Pagan). Using RQ (respiratory quotient) researchers can determine whether the horse is using fat or carbohydrate as a fuel source. Unlike oxygen, carbon dioxide varies tremendously with substrate (fuel) use. The RQ is calculated by dividing VCO2 by VO2. An RQ of 1.00 indicates that carbohydrates are being used as fuel, and an RQ of .7 indicates that fats are being used.

DESIGNING A TRAINING PLAN

By understanding the basics of equine exercise physiology, a racehorse trainer has the advantage of understanding how various physiological systems adapt and respond to training. In designing a comprehensive training plan for each horse the intensity, frequency, duration, and volume of the work is determined. The plan must also incorporate rest and recovery, and avoid overtraining. Each new level of training is maintained until the body has adapted to the added stress, after which further increase in training load can be applied. Alternating periods of increased workload with a period of adaptation is known as “progressive loading.” Training should be specific to the event in order to train the appropriate structures and systems, doing work that is similar to racing which elicits neuro-muscular coordination. Horses “learn” how to do the event. This principle of conditioning is known as “metabolic specificity.”

Most training programs are divided into three phases. Phase I is the long slow distance (LSD) phase, Phase II is focused around strength work, and Phase III involves sharpening and speed work. (Marlin and Nankervis, 2002) In Phase I, the primary focus is on long slow distance (LSD) and builds the foundation on which all other work is based. In their first year of training, Phase I may last from 3-12 months, with improvements in aerobic capacity seen in the first 6-8 weeks. Long slow distance is performed at slow canters at heart rates below 130-150 beats per minute. Even after this phase is completed LSD may comprise of 3-5 sessions per week lasting 20 minutes.

Phase I improves cardiovascular fitness and trains musculoskeletal structures decreasing the future risk of injuries. This phase also helps the horse’s mental attitude toward daily training. Phase I is primarily done at low intensities of aerobic levels. Phase II is the strength phase, where horses are trained with intensities from 150-180 beats per minute, and above 70% VO2 Max. Horses are usually working from a canter to a gallop over distances up to 1 ½ miles. This phase can be accomplished in 60-90 days. Aerobic and anaerobic systems are trained, with horses reaching anaerobic threshold levels during their workouts. These workouts over time will increase the time and speed at which lactate threshold is reached. Strength work may be performed 2 days a week with adequate rest between sessions.

Often in Europe hill work is added at this stage, increasing the intensity, without increasing the speed. Hill training strengthens the hindquarters, and working horses downhill strengthens the pectorals, shoulder, and working against gravity, the quadriceps in the hindquarters, become balanced. Phase III is the sharpening phase, where speed work is performed at heart rates and intensities at close to race speed, often reaching V200 and VO2 Max levels. Usually, depending on intensity, this type of work is performed only once every 1-2 weeks. Fast work can be performed as either continuous or interval training. Continous training performed at the racetrack involves distances from ¼, ½ mile, and 1 mile or more, usually with the last quarter at race speed. Interval training involves using multiple exercise bouts separated by relatively short recovery periods where the heart rate drops below 100 beats per minute.

CONCLUSION

Understanding basic equine exercise physiology and the metabolic systems of the horse not only benefits trainers, but owners, breeders and agents in training, breeding and buying a future thoroughbred athlete.

California Horse Racing Board explain their drug testing procedures

>The rules of racing are intended to maintain a level playing field; any drug testing program is meant to monitor compliance to those rules. In reality, drug testing is a deterrent. For truly illicit activity where the intent is to take an unfair advantage (cheat), the current program in California is working well. But we know it isn’t perfect. We are always looking for holes in the system and ways to improve the program.

The CHRB began conducting out-of-competition testing as a routine part of their drug regulation program in mid-February. Blood doping agents are the targets of this testing. Specifically, these are epoetin (Epogen®, Procrit®, “EPO”) and darbepoetin (Aranesp®). These drugs are synthetic forms of the natural hormone erythropoietin; they all stimulate red blood cell production. These drugs are administered several days in advance of racing and will not be detected in post-race testing. Out-of-competition testing is the only way these drugs can be identified. This is the reason out of competition is critical in human sports testing. Other prohibited peptide hormones will be included in the testing protocol as those tests are brought on line. We will not be testing for routine therapeutic medications, but we will be specifically testing for the synthetic hemoglobin Oxyglobin®.

Horses are selected for out-of-competition testing by both random and non-random methods. Non-random methods will have specific objective criteria to identify a group of horses. For example, last fall horses nominated to the Cal Cup was the selection criteria. Trainers will not be targeted by non-random methods without cause. We have tried to make the program as unobtrusive as possible. This is a new program; we welcome constructive recommendations to make the sampling process easier for everyone. A key element to this program is unpredictability so we will not be able to restrict testing to any specific day or days.

The CHRB will be expanding its program of freezing routine, cleared samples for retroactive testing. Retroactive testing will involve testing random samples with new tests or selecting specific samples based on specific information. If an illicit drug is being used for which we did not have a test at the time the sample was analyzed, we now have the ability to go back and re-examine the sample with a new test.


We are also in the process of developing the anabolic steroid testing program. Currently, nandrolone (Durabolin®), boldenone (Equipoise®), stanazolol (Winstrol-V®), and testosterone are Class IV drugs and will be handled as category D penalties (warnings) under the new penalty guidelines. All other anabolic steroids are at least Class III violations. We will be asking trainers and veterinarians to assist us in developing withdrawal time information to avoid future problems. Within the next 12 months, anabolic steroids are expected to be regulated in most states. Congressman Whitfield of Kentucky has introduced federal legislation requiring a total prohibition as opposed to the proposed regulation state by state.

A new website should be of use to trainers and veterinarians. The RMTC is hosting a site for withdrawal time information around the country for cooperative jurisdictions. The site is www.rmtcnet.com; go to the Withdrawal Times box and follow the instructions. These are the best available estimates at this time for California and many other states. Not all drug withdrawal times are available, but additional information will be added in the future as it becomes available.

Horsemen need to be aware several drugs remain problematic:

Fluephenazine is a long-acting tranquilizer. Two separate fluphenazine (Prolixin®) positives are working through the process where the administration periods were purported to be 14 days and 16 days prior to racing. These administration dates are supported by the veterinarians’ confidential reports. Unfortunately, fluephenazine has been shown to be pharmacologically active for over a month and is a Class II violation, a serious offense. This should raise concern for any trainer or veterinarian when fluephenazine is being administered anywhere close to a race. A 30-day withdrawal time is recommended as a minimum until more research information becomes available. Be aware this drug is confirmed in the blood rather than urine because of its unique elimination characteristics.

Hydroxyzine is a very useful medication for chronic allergies, including urticaia (hives) and respiratory allergies. Hydroxyzine metabolizes to ceterizine, which is also a pharmacologically active drug.  Hydroxizine is administered orally and the last two positives have been in powdered formulations prepared by a veterinary compounding pharmacy. As with all oral medications administered by barn personnel, mistakes are easy to make. A single oral dose of 250mg clears in 96 hours, but we have seen 8 times this dose on some prescriptions. The trainers have claimed they stopped the medication at 5 days in two of the cases. A seven-day withdrawal time may not be adequate at high doses or when using compounded preparations.

Methocarbamol continues to be a problem. We had suspected these violations were coming from compounded injectable methocarbamol with inconsistently formulated strengths. That may be a factor, but the most common finding is oral administration along with a methocarbamol injection at 48 hours. Again, oral administration increases the chance for management error and can be expected to extend the delectability of the drug in post-race samples.

TCO2 is still occasionally a problem, but we believe some violations may be inadvertent. We advise trainers to minimize and closely monitor their pre-race medication schemes, keep your horse well hydrated, and never administer an imbalanced or excessive electrolyte load. A significant number of horses have been administered one or another paste formulation of vitamins and/or electrolytes within 24 hours of the race. Many of these paste vitamin/electrolyte preparations contain bicarbonate or other alkalizing agents. Some certainly have high electrolyte concentrations. Be aware that these products are not permitted on race day. Oddly, there is a glaring disparity between northern and southern California. There has been about twice the rate of violations in northern California as in southern California, which was not case prior to last summer. We do know the pre-race medication protocols are different between the north and south. Regardless, the pre-race testing TCO2 program has worked well to deter the race day use of alkalizing agents. We have had only one trainer exceed 39 mmls/l since the CHRB took over the program and he received a 15-day suspension for the violations. The warnings letters for over 36mmls/l has also worked well. Prior to this program, the rate of samples 36.0mmls/l or higher was 1.4%; the rate is now at 0.2%.

Methamphetamine is a great concern to every regulator and should be to every trainer. This is our most common Class I violation. These are most likely from human derived contamination by someone in the barn having a “meth” drug abuse problem. This is a surprisingly common and cheap drug. We do not believe there has been intent to drug any of the horses, but amphetamines cannot be tolerated in horse racing for obvious reasons. The lightest penalty for the trainer to date has been a 120-day suspension.

There are several developments of importance to trainers in the enforcement and hearing process. The CHRB has been willing to settle cases administratively if a trainer so desires. Any settlement has to be mutually acceptable to both parties. Whether to settle a complaint or go to hearing is entirely up to the licensee. All settlement agreements must be approved by the Board of Stewards or the Board. As CHRB policy, all settlements are publicly announced. The other change we are seeking is in the hearing process where Class I, II, & III violations would be heard first in front of a hearing officer or the Board of Stewards rather than the Office of Administrative Hearings. This requires legislative changes currently under consideration in Sacramento. Lastly, the new penalty guidelines will soon be finalized. The penalties are significant for Class I, II, & III violations, but the hearing officer or Board of Stewards must take into account mitigating factors from the licensee and aggravating from the state. The intention is to allow a fairer process for the trainer or any other licensee charged in the complaint.

Lastly, under the new penalty guidelines with NSAID violations (phenylbutazone, flunixin, ketoprofen), the trainer can elect to deal directly to the Official Veterinarian with a set penalty schedule or to go to the Board of Stewards for a formal hearing. All penalties in this category call for higher fines than have typically been issued under the current process. Fines are significantly higher for multiple violations and especially high levels of the NSAID’s.

The CHRB’s hope is that the programs we have established will protect the integrity of our racing, be fair to all horsemen, and reduce violations over time. The goal is for California to have the cleanest, fairest racing in the United States.

Rick M. Arthur, DVM, - (01 July 2007 - Issue Number: 4)

Is no matter more pressing than international rules on medication?

By Geir Stabell

There is a need for several changes and improvements in international racing. None can be more pressing that the issue on international regulations on the use of medication. Both on and off the tracks."

Last year, we experienced a Japanese champion being disqualified after finishing third in the Prix de l’Arc. In Hong Kong, the sprinter Takeover Target caused some embarrassment when withdrawn from the Hong Kong Sprint, having failed pre race tests. In Dubai, the result of the Dubai World Cup had to be revised when runner-up Brass Hat was disqualified weeks later. Like Deep Impact, he had failed a post race test.
When discussing medication in horseracing, it would be unwise not to take the publicity aspect to the table. Last December, the Hong Kong international meeting was overshadowed by the debacle surrounding the absence of top sprinter Takeover Target. Leading up to the event, there was almost as much written on this horse alone, as on all the other contenders preparing for the big day.

Bad news sell newspapers and draws attention to web sites. Racing is no different. Horseracing folks around the world try hard to get more coverage in the media, often fighting a losing battle. When a horse breaks down, a jockey is injured or killed, or the words ”illegal substance” pop up in the press releases, there is no need to lobby the editors. They will print their take on the matter. And they will not do it in a kind way.  In stories regarding medication, you can call it a side effect, but make no mistake about it; this is a seriously detrimental side effect. The ”quest for excellence” – in international racing is beginning to get a high price.


Enhancing the breed?

How excellent is the horse that needs to be administered the painkiller “Bute” to win a championship race? How well suited to breeding is the horse that needs the anti-bleeding medication “Lasix” to race? Yes, these drugs are illegal when racing in Europe, but it is not illegal for a European trainer to administer these drugs to a horse when he is training it.

Is this a case of the racing authorities turning a blind eye to what goes on outside their own racecourses? Is it a case of the racing authorities not caring at all about how these animals are being prepared for appearances on their stage? Or is it a case of absolute naivety, in all corners of the racing communities, including the normally ever so sharp breeding industry? Either way, it is a recipe for more scandals, and perhaps also for more confusion among the horsemen.

Regulations on medication are very different around the world, giving trainers quite a headache when campaigning horses internationally. Brass Hat’s trainer, William Bradley, was convinced that he was within the rules when the horse ran second in the Dubai World Cup. Similarly, Yasuo Ikee, who trains Deep Impact, ran his star in the ’Arc’ feeling certain that any post race sample would not cause a problem. Both horses were subsequently disqualified from a valuable placing in each race. Both races have clear medication regulations, both trainers felt that they had followed the regulations surely disqualifications could have been avoided.

Medication qualifies for a run

Medication or no medication does not only play a part on the actual race day. At international meetings, a certain quota of the pre entered horses are ranked by a panel of handicappers. So, if the use of legal medications in the jurisdiction where a horse is based are performance enhancing, they also become a tool to help qualifying a horse for big races. Use of medication can help a trainer to get his horse qualified for a race, even for a race staged under rules not permitting medication. One strong stand to take, for organisers where medication is not allowed, would be to give preference in big races to horses that have not raced on medication. Perhaps the fact that a US based horse has been campaigned on medication, does not give him an edge when he runs free of medication elsewhere. Then again, if this is so, why would a European trainer administer medication when working their horses?


Hong Kong and USA

When Takeover Target tested positive before the Hong Kong Sprint , it was bad news for racing. It was truly creating a slandering effect when the press hammered home the fact that a favourite chasing a million dollar bonus was ruled out due to an illegal substance (in Hong Kong) in his system.
The race was eventually won by Absolute Champion, who had originally not been found good enough to take his place in the field. The handicappers placed him on the reserve list. He had never been raced on medication. Fast Parade, who made it into the selected field as one of the top names, had never run a race without medication. Some reports suggested that he had also failed a medication test on arrival. He was therefore never entered, officially as ”he was not doing well” after his trip to Hong Kong. He was shipped back home where, four weeks later, he produced his career best performance at Santa Anita. If Takeover Target and Fast Parade had taken their places in the Hong Kong Sprint, Absolute Champion would not have been a participant. He is currently officially the world’s highest ranked sprinter.


Is there a will to make a change?

Yes there is. At the Asian Racing Conference one report stated: "A growing need for uniform medication rules around the world was underlined by officials representing both racing jurisdictions and the International Racing Bureau."

Adrian Beaumont, of the IRB, pointed out that the explosion of international meetings had raced ahead of government protocols. Beaumont said that one of his main wishes for horseracing is ”a level playing field in terms of medication”. Mark Player, Hong Kong Jockey Club manager of international races, stated that medication rules should be made globally uniform if international series were to succeed and make the sport grow.  
 
Medication is also an issue for sellers and buyers of racehorses. February 8 this year may have been day one in groundbreaking work. On that day, a bill was filed in the Kentucky House of Representatives, that would allow buyers of horses to return the horse and demand a full refund, if veterinary records are falsified or information is omitted. Any administration of drugs would have to be disclosed. This bill is pushed by the Jackson’s Horse Owner’s Protective Association, formed by horseman Jess Jackson and lawyer Kevin McGee, who said:”The actual buyers and sellers of horses would like to see this in Kentucky because it would strengthen the integrity of the business. This would be an excellent way to encourage new owners to come into the business because it reduces the mystery of buying a horse.” 


Deaths, breakdowns and medication

How definable is the connection between use of medication and injuries? Taking a global view makes it almost impossible to come to any hard conclusions, as too many other factors play their part. Nevertheless, one should take not of the recent media focus on ratios of fatalities around the racing world.

According to professor David Nunamaker, at the University of Pennsylvania’s New Bolton Center, studies conducted at around ten American racecourses show that the rate of fatal accident in the US is 1,5 in 1,000 starts. This may seem small but even a high profile track suffered from much worse stats last year: 21 horses died during the three-month meeting at Arlington Park outside Chicago. The track had a total of 7,013 starters, producing the grim figure of 3 fatalities in 1,000 starts.

Yes, this was well covered by the non-racing media in Illinois.How this affected business, is hard to say but the on-track wagering at the meeting fell by 14.5% compared to 2005. The average attendance figure was down from 7,607 in 2005 to 6,903 in 2006.

How do these figures of fatalities compare to the rest of the world? Many point out how much better the situation is in Hong Kong, where no form of medication is accepted. They have a fatality rate of 0,58 in 1,000 starts. In England the figure is reportedly 0,65 deaths per 1,000 starts.

Medication alone is not to blame for breakdowns and fatalities in American racing. Other factors are racing on dirt tracks, juvenile racing, and the fact that the country’s vast horse population means that there is a much higher proportion of very moderate horses in action. Furthermore, comparing US racing to racing in Hong Kong make little, if any, sense at. Not least since the HKJC does not stage juvenile racing and the fact that they race exclusively on turf.


’Cheaters’ not so clever on turf?

Gary Dutch, Racing Secretary at Hawthorne Racecourse, Arlington’s little brother on the other side of Chicago, has some interesting comments: “I don't believe medication affects the breakdown rate”, he says, “I believe that it is caused by too many sprint races under six furlongs and two-year-olds racing over two furlongs too early in their careers. What these horses are learning is speed, speed, speed! ”

“I am sure that there are so called 'wonder drugs' some trainers are using as are professional athletes to enhance performance doing. These 'cheaters' are always a step ahead of testing and have an edge. You can't test for something that you don't know exists.”

Dutch goes on to make an interesting point about dirt racing compared to turf racing:

“The only difference is that some high percentage dirt trainers have a poor win percentage on turf. Why I don't know. Turf racing is more formful as turf horses will win the turf races. Dirt horses or horses that are not bred for turf usually are automatic throw-outs.”


Lasix and Bute ’overrated’?

European trainers shipping to North America can run horses on medication. Many European trainers sending a horse to a big race in USA, runs the horse on Lasix. ”First time Lasix” is a well-known phrase among American horsemen and horseplayers. It can often explain a horse’s improvement in a race. Many believe it will always improve a horse’s performance.

If so, one would think that running a horse without the help of medication at the Breeders’ Cup, was a sure fire recipe for defeat. After all, with the top trainers in USA taking their best horses, and many of the finest horsemen in Europe doing the same – and adding Lasix – he or she who decides to go without would stand no chance whatsoever. Not so. In fact, the one trainer who has refused to run his horses on medication, Andre Fabre, has a Breeders’ Cup record pretty close to the best of the Americans. And his record is way better than those achieved by some of the numerically strongest operations in the US. Even those who have been sailing so close to the wind in the medication game, that they have paid the price through fines and suspensions.


 
Over the years, the French trainer Andre Fabre has run 39 horses at the Breeders’ Cup, and won with four of them. 10.2% of Fabre’s runners were winners. None of them ran on medication. The most successful trainer in the history of the Breeders’ Cup, D. Wayne Lukas, has saddled 146 runners at the meeting, with 18 winners to date. This gives a strike rate of 12.32%.

The simple truth is that Fabre has been as good as the best Americans at the Breeders’ Cup, despite the meeting falling after the ’Arc’ weekend and is thus not his main priority, despite the fact that he is at a disadvantage geographically, and despite the fact that he has never run a horse on medication. While several horsemen in the US believe that Lasix is virtually the most important factor in their quest for success, one man alone, training racehorses in Chantilly, seems to have proven them totally wrong. Other Europeans have run big races at the Breeders’ Cup when racing on medication. Perhaps they would have run just as well without?

People are quick to point at one odd result, or a few winning ex-Europeans in the US, and claim that there in lies the proof that racing on Lasix improves horses’ performances. Much was made of Miss Alleged’s win in the 1991 Breeders’ Cup Turf, when the French filly was racing on both Lasix and Bute. Based on previous form, she was an absolutely shocking winner. She had raced once in the US previously, when fifth in the Washington D.C. International two weeks earlier. Her win over Itsallgreektome at Churchill Downs was lengths better than her performance at Laurel, and also much better than what she had achieved in France, where she had been placed in Group races but could manage only 11th when running in the ’Arc’. It was reported that she burst a blood vessel at Longchamp that day. Was the anti-bleeding medication Lasix added for the first time on Breeders’ Cup day? No, it was not. The filly had also raced on Lasix when well beaten at Laurel Park.

This is not at all the only example of a European horse that has produced contrasting performances on consecutive starts when aided by medication in North America. Sometimes horses run up to form when they are supposed to, sometimes they don’t. Strangely enough, this is the case also for horses racing on medication. Can you think of a better ”selling point” - for those who are working towards a medication free horseracing world?


The importance of worming - keeping parasites under control

The use of homespun and herbal remedies may have been superseded by wormers formulated after lengthy research programmes, but the control of worms in the horse remains as important for horsemen today as it was when the significance of these unwanted passengers was first understood.

The main internal parasites of the horse are small red worms (Cyathstomins), large red worms (Strongyles), round worms and tapeworms. The worms undergo similar lifecycles: Larvae and eggs are ingested by a grazing horse and they mature within the gastrointestinal tract. The adults pass out eggs and immature stages in the dung which reinfect the pasture, allowing the cycle to be completed. Infestations with Bot Fly larvae may also be seen.
The development of all these parasites within the equine gut has the potential to cause clinical problems, including colic and ill thrift. However, the lifecycle of the cyathastomins can be particularly destructive.  Cyathostomin larvae actually grow and develop within the wall of the horse’s intestine, causing disruption to the highly specialised intestinal cells. In addition, the larvae have the ability to arrest their own development, entering an encysted or hibernatory phase within the gut wall. Importantly, during this encysted phase the larvae are relatively impervious to a number of common antheImintics (wormers) and over time the parasite burden on the horse may accumulate, with large numbers of larvae entering the encysted phase.
Following the encysted phase, the larvae continue their development by growing and literally bursting out through the gut wall to mature into adults within the lumen of the gastrointestinal tract. However, a cruel twist to the cyathastomin lifecycle is that thousands of encysted worms appear to coordinate their emergence from hibernation, usually in the spring. Large numbers of larvae emerging at once can give rise to a variety of clinical signs from slight lethargy, anaemia and weight loss through to spasmodic or obstructive colic.  Large areas of damaged gut may be replaced by scar tissue instead of the specialised, absorptive cells of the intestine, potentially resulting in weight loss and diarrhoea. Our equine athletes must be able to utilise the high quality (and expensive!) feeds we offer them, and this necessitates a healthy gastrointestinal tract. Thankfully, it is unusual to hear of parasite-associated mortality in racehorses but it would be interesting to know the contribution  made by infestations to sub-optimal performance or training days lost.
It has been accepted for many years that the routine worming of horses is important for their health. This is especially true in establishments with a young and constantly changing population of horses, or pastures which are heavily stocked or grazed by multiple horses. Although all of these conditions are likely to prevail in racing yards, parasite-associated problems could formerly have been dismissed as irrelevant to the well-organised yard with a sound worming policy. Unfortunately, things are now not so simple and it appears that the worms are fighting back. Keen to ensure the survival of their own  kind, they are evolving new strains that are resistant to some anthelmintics. It is not scaremongering to say that some horsemen may soon have no effective means for controlling the internal parasites affecting their charges.
Resistance can occur when any chemical is regularly used to control an infective organism, hence the problem of bacteria resistant to several types of antibiotic found in hospitals e.g. MRSA. In some cases ‘operator error’ may be to blame for encouraging the development of resistance. Incorrect dosing (particularly under-dosing) with anthelmintics may promote the evolution of resistant worms.
Only three classes of anthelmintic are licensed for use in the horse and red worms resistant to the benzimidazole group are common in thoroughbreds. Pyrantel forms the second class. Strongyles resistant to pyrantel developed in the USA where it was used as a feed additive. They are increasingly recognised as a problem in Europe. More worryingly, resistance is developing to the third and final class of wormer, the macrocyclic lactones (ivermectin/moxidectin). Round worm control in foals is not guaranteed by their use and cyathostomins resistant to them are now present on a donkey sanctuary in the UK. Evidence for  cyathstomin resistance has also emerged from Brazil and Germany. It may be the case that resistance has not been detected in more countries due to lack of testing, rather than no resistant parasites being present.
Clearly, planning the worming regime is of the utmost importance and requires detailed knowledge of the strengths and weaknesses of different worming products. However, in a telephone survey of English racehorse trainers in 2002, only 42% stated that their choice of anthelmintic was based on veterinary advice. Furthermore, the same study suggested that strategies used for the treatment of new arrivals were unlikely to prevent the introduction of resistant worms or the development of encysted red worms in the majority of cases.
It is also known that the parasite burden of horses in a yard is not distributed evenly. Most horses will be relatively worm-free. However, one or two ‘wormy’ individuals will be contributing the majority of eggs to the pasture. Identifying these individuals is done by performing faecal worm egg counts (FECs) regularly on all horses within the yard. This could also facilitate a change in the way wormers are used on training yards, moving away from pre-planned blanket dosing of the whole yard to treating only those individuals which require it. Current thinking would suggest that only horses with FECs in excess of 200 eggs per gram (epg) should be treated. An important point to make regarding FECs is that they do not detect encysted/immature red worms.
It is also possible to establish the resistance status of the worms in the horses on the yard. FECs are performed at the time of treatment and repeated afterwards to ensure that the wormers have worked, the faecal egg counts have been reduced and that the horses don’t harbour resistant populations of worms. In the case of pyrantel, the FEC should be repeated seven days later and resistance should be suspected if the FEC is reduced by less than 90%. For benzimidazoles, the count is taken 14 days later and the FEC should be reduced by over 95%. The interval for ivermectin is 21 days and FECs should be less than 1% of the previous level if resistance is not to be suspected. The persistence of Moxidectin makes it unsuitable for this type of test.
Tapeworms have been implicated as a factor in cases of colic. Work at Liverpool University has lead to the development of a test for the presence of tapeworm which can be performed on a blood sample. This indicates if treatment is necessary and can be repeated to check that anthelmintic treatment has been successful.
Although this monitoring may appear to be time-consuming, it would allow a very accurate picture of control programme efficacy to be established. The use of expensive anthelmintics is curtailed and selection pressure for resistance on the parasites is reduced.
As previously mentioned, a protocol for new horses on the yard is extremely important. Recent arrivals should be confined to their box, or allowed access only to a quarantine paddock. An FEC should be performed. It is best to assume that the animal is carrying encysted red worm larvae and to treat for these with moxidectin or five daily doses of fenbendazole. If later FECs suggest the presence of resistant worms, the horse should be assigned its own paddock, or returned to where it came from.
When worming any horse, it is important to follow some basic guidelines to ensure the correct dose is administered. Anthelmintics, or any other drugs, should only ever be given by the route prescribed on the data sheet. An accurate weight should be obtained for each horse to be treated and the full dose for that weight given. If there is any doubt about the accuracy of the weight i.e. obtained by measuring tape, then it is best to slightly overestimate the dose. Ensure that each horse ingests their full dose of paste by holding the head up until it is swallowed. Giving inadequate doses of wormer may hasten the selection of resistant parasites. Animals identified as requiring an anthelmintic treatment which share grazing should receive synchronised treatments. This will help to prevent an immediate major reinfection. It is now advised that, where more than one class of wormer is still effective, they should only be rotated on an annual basis.
Worm control is not all about the use of anthelmintics and these alternative strategies assume an even greater importance with the advance of resistant parasites. They mainly involve reducing the level of contamination on the pasture and so preventing the worms from completing their lifecycle in the gut of the horse. The most direct method is to remove faeces from the grazing, ideally twice weekly during the summer and once per week over the winter. This can be done manually or by machine.  Sheep and cattle will ingest the equine parasites, but are not themselves affected and so clean the grass for horses. Simply lowering the stocking density on the pasture will also help.
Thoroughbred breeders may also have a role to play in worm control. Faecal egg counts may not be the first thing that comes to mind when planning matings, but that may have to change. Resistance is developing to our third and final class of anthelmintic and no new wormers licensed for equines are likely to be on the market in the near future. We know the debilitating effects of an untreated, or possibly untreatable, worm infestation. A horse carrying a heavy infection would never be able to realise its full potential. So, without a major re-evaluation of anthelmintic use, it may be that the classic winners of tomorrow are descended from the innately parasite-resistant individuals of today.  

Dr Philip K Dyson BVMS Cert. EM and Barry Sangster BVMS MRCVS
 (19 May 2007)

Shockwave Therapy - uncovering new treatments

Doctors originally used shockwave therapy more than 20 years ago to disintegrate kidney stones in their patients, then learned that the therapy can also treat tendonitis, tennis elbow, heel spurs and other ailments. Equine researchers are still uncovering everything shockwave therapy can do for horses after it was initially and successfully used in Germany in 1996 to treat lameness. Shockwaves are high-pressure, low-frequency sound waves generated by a device outside the body and focused on a specific body site. When the shockwaves meet tissue interfaces of different densities, the energy contained in the shockwaves is released and interacts with the tissue, triggering natural repair mechanisms and stimulating bone formation and blood flow.

The shockwaves can lessen or eliminate pain and accelerate healing. New York trainer Rick Schosberg has a unique perspective on shockwave therapy. He’s used it on himself and his horses. “I’ve used it for myself for tennis elbow; it helped my elbow for 90 days,” Schosberg said. “With my horses I’ve used it a couple times on injuries and it did okay for minor injuries, soft tissue and saucer fractures. It probably knocked a third off the healing time but it’s expensive. You use it for at least three treatments over a month and a half, usually every two or three weeks. As long as it‘s not abused it’s okay. You can‘t run a horse within 10 days after you use it and you have to report it every time you use it (in New York) because it has an analgesic effect.” Shockwave therapy’s impact on horse racing could not have happened if it wasn’t developed for human patients first. And that happened by accident. During experiments with high-velocity projectiles, which were being used to smash ceramic plates, an employee at a company in Germany touched the plate at the very moment the projectile hit the plate. He felt something in his body akin to an electric shock, though measurements showed that there was no electricity present. That prompted German scientists to begin researching the possible effects of shockwaves on humans in the late 1960s. The first successful disintegration of a kidney stone in a patient by shockwaves was done in 1971. Fourteen years later, experiments were conducted regarding the effect of shockwaves on bones, leading to experiments on other parts of the human anatomy.

Today, shockwaves are the first choice of treatment for kidney and ureteral stones and has morphed into treatment for other medical conditions. Will equine medicine’s use of shockwaves follow a similar pattern? The first equine disease to be treated with shockwaves was proximal suspensory desmitis, an injury to the suspensory ligament which is a major cause of lameness. A year later, shockwaves were used on a horse with Navicular Syndrome, an ailment affecting the small navicular bone in a horse’s foot and the connecting ligament. The first use of shockwaves in the United States happened in 1998 with a horse with a distal hock joint and navicular pain. All the results were encouraging. “When we first started using it, it worked okay on lameness,” Iowa State University’s Dr. Scott McClure, DVM, a leading researcher of equine shockwave therapy, said. “At this point in time, it’s been well documented for tendon and ligaments.

A lot of people think it works for stress fractures. I think there are some joint applications which we’re learning more about. Soft tissue, too. It’s been shown to increase permeability of cell walls.” He believes that increased cell wall permeability could lead to drugs which are more effective attacking tumors. “There’s potential for a lot of applications,” McClure said. “I clearly don’t think we understand all of its uses.” There are two types of equine shockwave therapy: extracorporeal generated outside the body and focused on a specific area of a horse’s body, and radial pressure waves when an applicator is pressed on the horse’s body. “The two of them get lumped together, but they shouldn’t be,” McClure said. “They’re very different. Radial pressure waves have lower pressure and more shallow penetration.” According to Dr. Stephen Adams of Purdue University‘s Veterinary Teaching Hospital in a 2002 article, studies have shown that shockwave therapy is effective treating suspensory ligament disease, bowed tendons, ringbone, bone spavin, splints, fractured splint bones, sore backs, navicular syndrome and fractures not healing properly. “Initial studies show that about 75 percent of horses treated for these conditions show marked improvement following shockwave therapy,” Adams wrote, while noting that many conditions require a second treatment to produce optimum results. “Advantages of this treatment are that no drugs are used, and horses with chronic conditions such as bone spavin, chronic suspensory ligament disease and navicular syndrome can continue to exercise.

Frequently, improvement in lameness is achieved in horses where conventional treatments have failed. Shockwave therapy is used as an adjunct treatment for fresh injuries such as recent bowed tendons with the goal of reducing convalescent time and improving the outcome.” On its website, the University of Wisconsin-Madison’s Veterinary Medical Teaching Hospital suggests using shockwave therapy on horses suffering from: suspensory ligament injury, tissue calcification, fractures or joint ankyloses, fatigue injury to bone, back pain, navicular disease and bone exostosis.

McClure documented the effect of extracorporeal shock wave therapy (ESWT) on horses with unilateral forelimb lameness in a study he co-authored with Jessica Dahlberg, Richard Evans and Eric Reinertson which was published in the July 1st, 2006 issue of the Journal of the American Veterinary Medical Association. The study focused on five geldings and four fillies and mares with lameness.

Treatment by ESWT resulted “in a period of acute improvement in lameness severity that typically persists for two days. Thus, in horses undergoing ESWT, exercise should be controlled for a minimum of two days after treatment to prevent further injury.” The reason is that ESWT has an undeniable analgesic effect. “This has raised concerns that use of ESWT to treat musculoskeletal injuries in horses may, because of the analgesic effects, result in overuse of the injured limb, causing further injury to the affected part and posing a risk to treated horses and their riders,” the study said. “For this reason, racing jurisdictions in the United States and the Federation Equestre International have adopted regulations that require a 5-to-7 day period after treatment before the horse is allowed to perform.”

Regardless, the horseracing industry, one never known to embrace change and new products, has quickly come on board in using this non-invasive treatment on their horses. “Over the last five years, it’s dramatically increased,” McClure said. “The market is starting to saturate. There’s a lot of equipment out there. In 1988, I had the second machine in the country. I think the owners and trainers have taken the bit and run with it. They’ve been very aggressive with that.” Trainer Sanna Hendricks used shockwave therapy on her multiple stakes winning steeplechaser Praise the Prince after he suffered a soft tissue injury below the pastern while winning the 2003 Grade 1 New York Turf Writers’ Cup at Saratoga Race Course. “We used shockwave therapy on him, and he responded to it,” Hendricks said in an August 30th, 2004 story in the Blood-Horse. “I took the conservative approach with him. I gave him plenty of time to rest and recover and didn’t bring him back to training until February 5th with an eye on these races at Saratoga.” Praise the Prince not only made it back to the races at Saratoga, he won the 2004 Grade 2 A.P. Smithwick Memorial Steeplechase there as a nine-year-old. If that isn’t an endorsement for shockwave therapy, what is? But shockwaves should not be construed as a panacea.

Complications can occur with incorrect use, and McClure wrote, “The release of kinetic energy at interfaces of different acoustic impedances is crucial in planning ESWT. Shock waves must never be focused on gas-filled cavities like the lung or intestine.” Meanwhile, he’s back at work, doing new studies to see just what else shockwave therapy may help.

Nutritional Support for bone - maintaining a strong skeleton

The expression ‘no foot no horse’ should perhaps be extended to cover all the bones of the skeleton, for as far as racehorses are concerned, without strength and durability in this area a trainer’s job is fraught with difficulties. The number of training days lost to lameness in a season is testament to this. A racehorse’s diet should help to maintain the skeletal system during rigorous training. This task is no doubt easier when the skeletal foundations have been firmly laid in utero and during the rapid growing phase.

The formation of cartilage and its subsequent conversion to bone ‘proper’ is one of the key processes to highlight. Long bones develop in the foetus from early bone templates that are composed entirely of cartilage. Conversion of cartilage to bone occurs initially within a central area of ossification (bone formation) within the long bones, known as the diaphysis and then also at each end of the bone (epiphysis). There are various abnormalities that can occur during the development of bones and joints that may involve problems during the localised conversion of cartilage to bone, or with bone lengthening, or changes within the bone after it has formed, once a horse has commenced training. Nutrition is only one of many factors involved in DOD Osteochondrosis (OCD) involves disruption to the normal conversion of cartilage to bone within the areas of ossification. For many years, researchers viewed nutrition as the key to OCD, however, it is now recognised that genetic predisposition, body size and mechanical stress, as well as trauma are all additional factors that must be considered.

Whilst diets that simply oversupply energy have been demonstrated to increase the incidence of OCD, the previously hypothesised causal link with excessive protein intake has not been proven. This suggests that the source of the energy in feed is an important issue. Recent research supports this, as it has been reported that diets with a high glycemic nature, i.e. those with a high starch and sugar content (typical of the more traditional stud and youngstock rations), appear to be more likely to trigger OCD. However, one would suspect that this would be more apparent in genetically susceptible animals. Many mineral imbalances in the diet have also been implicated as causative factors in OCD, but few have any strong evidence to support their role. For example, OCD lesions have been reproduced experimentally in foals maintained on a very high phosphorus intake.

This type of diet could arise inadvertently by feeding straight cereals such as oats, without a suitable balancer or complementary feed such as alfalfa to redress the low calcium to phosphorus ratio in the grain. Less extreme versions of this diet could occur through excessive top dressing of ‘balanced’ coarse mix or cubes with additional cereals such as oats or barley, as is common practice in many yards. A low copper intake, especially during the last trimester of pregnancy, has also been implicated in OCD. Copper has received particular focus due to its functional role in the activity of a key enzyme involved in formation of the collagen cross-links. However, other trace minerals including manganese and zinc may be equally important during this key stage in a foal’s development in utero, as they are necessary co-factors for important enzymes involved in regulating cartilage metabolism. Blood tests that challenge the premise that horses are unaffected by molybdenum levels in grazing In grazing youngsters, a secondary copper deficiency can be caused by excessive molybdenum levels in pasture. In cattle, bacteria in the rumen form complexes between molybdenum and sulphur.

These thiomolybdate complexes will bind copper within the gut and when absorbed will then search out further copper to bind, either circulating in the blood or in association with copper dependent enzymes. This can severely impair the activity of some key enzymes involved in growth processes and cartilage turnover. However, as a horses gut is somewhat different from a cow’s, in that the hindgut (the equivalent of the rumen) is positioned after the small intestine and not before, there is theoretically less opportunity for these thiomolybdates to be absorbed and ‘cause trouble’. At least this is what has been largely accepted from previous studies in horses that focussed on plasma copper levels and copper absorption. However, new blood tests that can be used to measure the activities of key copper dependent enzymes, such as superoxide dismutase (SOD), in conjunction with traditional measurements of plasma copper status and the presence of thiomolybdate complexes suggest that this may not always be the case.

Dr Stewart Telfer of Telsol Ltd, routinely carries out such tests in cattle and has to date analysed about 100 samples in horses suspected of having an issue with molybdenum interactions. He says, “From our work, it is clear that horses do suffer from molybdenum (thiomolybdate) toxicity. The interactions between copper, iron, molybdenum and sulphur will take place in the horse’s gut and in certain situations, not always linked to a high molybdenum intake, will result in the horse suffering from molybdenum (thiomolybdate) toxicity. Dr Telfer however, acknowledges that only relatively small numbers of samples in horses have been tested and the laboratory does not currently have a definitive reference range for horses. Calcium and phosphorus may be mobilized from bone to compensate for ‘acidic diets’ When yearlings first move into training yards, they usually experience a significant change in their diet that has consequences for bone metabolism during this period in their lives when some continued growth occurs and the skeletal system is put under considerable strain. In general terms, a ‘stud diet’ has what’s called a high dietary anion to cation ratio (DCAB).

This is largely due to the high inclusion of ingredients like soya and forages. A ‘full race training diet’ on the other hand tends to have a much lower DCAB (is more acidic) due to the reduction in forage intake and higher inclusion of cereals such as oats. The significance of a low DCAB is that it reduces the efficiency of calcium absorption and retention within the body and may contribute to the reduction in bone density seen in horses in early training. This surely is an argument for limiting the intake of cereals and maximising forage intake during the early stages of training when a high cereal intake is largely unnecessary. Calcium is the most abundant mineral in the horse's body, with the majority being present in the skeletal system. Phosphorus is also found in large amounts in bone in close association with calcium.

A racehorse’s diet should provide an adequate intake of both minerals but also needs to provide a balanced calcium to phosphorus ratio of near to 2:1. Although exercise demands a slight increase in calcium intake above the requirements for maintenance, this is usually satisfied by the generalised increase in feed intake. However, the efficiency with which individual horses absorb calcium varies and should certainly be investigated when a calcium-related issue arises. This can be achieved by examining an individual horse’s calcium and phosphorus status, by looking at the diet and also within the body using a creatinine clearance test. Topdressing – a national pastime When using straight feeds, or when topdressing ‘straights’ onto a ‘balanced’ racing mix or cubes, be aware that certain types of feed are much higher in calcium relative to phosphorus and vice versa (see table). Alfalfa, with its high calcium to phosphorus ratio, makes an ideal partner for cereals, which are low in calcium relative to phosphorus. Conversely, the traditional combination of oats and bran is not ideal, as it combines two feeds, which are low in calcium.

Remember that you can use a supplement or feed balancer to carefully correct any deficiencies or imbalances when feeding straights. Equally excessive addition of oats to a balanced mix or cube can decrease the calcium to phosphorus ratio sufficiently to cause problems. Most commercial mixes or cubes have sufficiently high calcium to phosphorus ratios to practically be able to withstand the addition of 1-2kg of oats daily, however any increase beyond this is unwise without further corrective measures. Feeds High in Calcium &Low in Phosphorus Feeds Low in Calcium & High Phosphorus Alfalfa Oats Sugar Beet Barley Seaweed Maize Wheat Bran Horses have a complex regulatory system, involving certain hormones, for ensuring that the proportion of calcium in the body, relative to that of phosphorus, remains stable and that the level of active or ‘ionised’ calcium in the blood remains within tight limits. If for one reason or another the level of calcium relative to phosphorus in the blood drops, a number of safety systems will be triggered to redress the balance. Bone acts as a reservoir of both calcium and phosphorus, which can be drawn on when necessary. The body's balance of calcium and phosphorus is continually 'corrected' by either conservation or loss of calcium or phosphorus in the urine, via the kidneys or through the skeletal system. Sustained calcium and phosphorus imbalance can, however, contribute to developmental orthopaedic diseases (DOD) in young horses, or lameness and sometimes bone fractures in mature horses. Research shows silicon is a trace mineral worth a second look.

Moving on to a less well-recognised trace mineral as far as bone is concerned, there has been some interesting research carried out into the effects of supplemental silicon in the racehorse’s diet. Silicon is a natural constituent of plants and provides structure and rigidity to some of their cell walls. It therefore forms a natural part of the horse’s diet, however, the availability in horse feed is apparently limited. Silicon plays a role in the development of new bone and is also important for the calcification process. It is therefore a relevant micronutrient for horses in training, as bone is dynamic and is constantly undergoing change, in response to forces placed upon it during the training process.

Research carried out by Dr Brian Nielsen at Michigan State University in the early nineties reported a dramatic decrease in injury rates in quarter horses fed a bioavaiable form of silicon as sodium zeolite A. This program of research has also established that the silicon is available to foals via the milk of supplemented mares. However, thus far the group have not uncovered the mechanism by which the beneficial effects of silicon are brought about. However, the form in which sodium zeolite A is fed (a chalk like powder) and the level of intake used in these studies (about 200g per day for a 500kg horse) makes it impractical to use as a feed supplement unless it can be incorporated within a feed pellet. In conclusion, attention to those factors within the diet that support bone turnover is likely to contribute to a reduction in injuries observed, however, the implementation of appropriate training techniques and use of suitable training surfaces also has a huge impact on the durability of horses in training in comparative terms.