Bones of contention - how to maintain a strong skeleton

By Catherine Dunnett

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 


Alfalfa, Sugar Beet,  Seaweed


 
Feeds Low in Calcium & High Phosphorus

Oats, Barley, 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.

Dermatologic conditions that affect thoroughbred racehorses

Horses are similar to many other species with the skin being the largest organ in the body.  This is based on overall organ size; just think about the total surface area of a 600 kg horse!  The good news is that it can be easily evaluated by visual inspection and palpation.  Specific tasks for equine skin include protection from trauma, thermoregulation (temperature control; sweating and heat conservation), sensory perception, secretory function and pigmentation.  In addition, it is important to recognize that skin is an important indicator of systemic health since disorders of the skin may actually indicate systemic ill health.

Hives (urticaria)
Of all domestic species horses show evidence of hives most often.  The technical veterinary terminology for hives is urticaria.  In some cases horses will have a condition of recurrent or repeated bouts of hives.  The skin lesion itself is an indication of allergic reaction.  This is not a specific disease, yet it is a clinical sign of a systemic problem.  In some cases this may be a very serious condition such as after drug treatment, vaccination or insect bite.  Other times it is a more mild condition associated with an air-borne allergen.  The size of the bumps, how rapidly they develop and the contact they have with one another are all important characteristics of the condition in determining the severity of the problem.  Those that occur rapidly, enlarge quickly and touch with one another (coalesce) are the most severe.  Figure 1 shows examples of mild (individual) and severe hives (coalescing) lesions in two different horses.
The cause of hives is somewhat complicated.  Specific immune cells called mast cells and basophils are the source of the proteins that result in hive formation.  The primary protein released from these cells is called histamine.  Once the allergen is present in the host, either by contact, ingestion (by mouth) or inhalation (by the respiratory tract) a series of events occurs that results in the release of inflammatory mediating proteins that include histamine.  The effects of these proteins are increased leakage from blood vessels, increased recruitment of white blood cells to the area of inflammation and hive or wheal formation.   Immunologic or hypersensitivity reactions to dugs, ingested material, or inhaled pollens or dusts are potential sources for allergen exposure.  The most common medication to result in hives is penicillin.  Air borne allergens may be certain types of pollens or molds or specific feed types.  Alfalfa is a forage source that results in allergy in certain horses, the horse pictured in Figure 1 (lower panel) is suffering from hives as a result of allergy to alfalfa hay.
Definitive diagnosis of the cause of hives can be challenging.  Many times symptomatic therapy is required for the initial stages of disease and following anti-inflammatory therapy the lesions will disappear.  In cases where the lesions recur, diagnosis may be required.  The most effective method of making a diagnosis is to skin test the individual with a series of different allergens.  Once the allergen (s) is / are defined they must be eliminated from the horse’s environment.  This can be very challenging to accomplish for certain air borne or particulate allergens.  In cases where elimination can not be accomplished, symptomatic therapy may be required intermittently.  An example of recurrent disease may be associated with certain insects during warm months of the year; lesions will recur as long as insect bites continue to occur.  Once the seasons change then the insect population will regress and lesion development will be less common.  Horses maintained in warm climate environments may have more problems with clinical disease associated with warm weather insects or pollens.
Treatment with a low dose of allergen over a period of many weeks to months has been used in people and small animals to reduce immune responses to antigen stimulation.  This process of reducing immune reactivity is called hyposensitization.  Hyposensitization may be attempted in an effort to reduce the reactivity of the horse’s immune system.  The response to this treatment may take weeks to many months to see an improvement.
The goal of management of affected horses involves elimination (or control) of exposure to inciting allergens.  Symptomatic anti-inflammatory therapy under veterinary guidance is needed when lesions are present. Once the allergens have been identified and controlled development of lesions and clinical sings may be achieved.
Pastern dermatitis
Scratches, sore heel, pastern dermatitis, and grease heel are all names of a similar disorder that affects horses undergoing frequent moist conditions.  As a result of race horses requiring frequent baths it is common under training conditions for pastern dermatitis to occur.
Crusting and flaking associated with scratches occurs on the back side of the pastern in one or several limbs (Figure 2).  Although it is common to start as a small circular lesion, the lesions often enlarge to become ulcerated lesions on the pastern.    The condition commonly begins on a white limb and then may spread to involve other limbs.
It is important to identify if a topical irritant may be responsible for the initial lesion.  If this is the case the irritant material should be thoroughly washed off and the limb(s) dried.  Not uncommonly the initial lesion is a minor irritation and secondary complications occur from opportunistic bacterial infections.  The secondary complications can make this condition extremely difficult to clear.  Local cleansing and keeping the limb dry will often be curative.  Thick emollients should not be applied, the most important aspects of managing this condition is keeping the limb(s) clean and dry without adding topical irritants or materials that will retain moisture.
In severe cases antibiotic therapy may be necessary and therefore veterinary consultation is recommended.  Severe disease may require additional diagnostic tests to be performed such as skin biopsy for histologic analysis and bacterial / fungal culture.  In some instances a definitive cause can not be identified and care with cleaning the limb and keeping it dry will improve the condition.
The goal of managing a horse with scratches is to keep the affected areas clean and dry.  Avoid application of topical emollients since these agents will retain moisture in the affected areas.  In severe cases veterinary attention may be required to completely clear the infection with antibiotic therapy.
Dermatophilosis
One of the most important skin conditions in horses involves bacterial infection with Dermatophilus congolensis.  Characteristics of this condition include matted hair, skin crusting, scab formation and hair loss.  Most commonly horses that suffer from this condition are maintained in prolonged moist conditions, occasionally horses that are maintained under dry conditions develop this disorder.
The area where the lesions may be observed are usually over the head, neck, and sides of the belly or chest.  More localized disease may occur over the top line (back) region or on the cannon bone of the hind limbs, particularly in race horses.
Signs associated with this condition may be local or generalized and include hair loss and skin crusting, without itching.  When the condition is severe horses may show signs such as depression, poor appetite, weight loss or fever.  When this condition occurs on the head or legs the areas of white skin are more likely to be affected.  When horses have a thick coat the crusting scabs are more easily felt than seen, the crusts are located deep in the coat next to the skin surface.   When the crusts are removed pus material may be observed on the skin or crust.  These lesions can also occur on short coated horses during summer months.  The cannon bone condition in race horses occurs in warm moist conditions.  Small matted hair patches are observed down the front of the cannon bones.
The diagnosis can be made by careful examination, findings that are consistent with those described, and microscopic analysis of the crusts.  In suspect cases bacterial culture can be used to confirm the diagnosis.
Treatment of this condition requires careful cleaning of the affected area and removal of scabs.  It is important to recognize that this is the result of a skin infection and the skin may be very painful to touch, therefore removal of scab material may be strongly refused by the horse.  In severe cases, veterinary aid should be implemented to allow for safe and effective removal of scab material.  Gentle washing should include a dilute betadine or chlorhexidine scrub (surgical scrub).  In some instances soaking scab material with warm water will facilitate removal and will not meet with severe objection by the affected horse.
Infections that involve white skin may be associated with secondary light sensitivity, so that the horse develops a severe sun burn.  Protection from sunlight is recommended in such cases, if the horse must be outdoors, then powerful sun block (SPF 25 or greater) should be applied.
When this condition is present on the lower limbs bandaging should be used with caution.  The presence of the bandage material will promote a dark, moist environment, which will prolong healing time.  Clean and dry limbs will be most likely to heal.  Contact with wet bedding material or surfaces (wet grass) should be avoided until the lesions have healed.  Scar formation may occur with longstanding disease; this will possibly lead to skin cracking and reinfection.  If lameness occurs at any point veterinary consultation should be sought out immediately.
Dermatophilosis is a skin infection that results in crusting and cracking, which involves the cannon bone in race horses.  Mild cases respond well to dry, clean conditions.  In more severe cases antibiotic therapy may be required.  Caution should be implemented when affected horses are handled because lesions are typically painful to touch, making affected horses potentially dangerous to work with.
Dermatophytosis
Ringworm is a highly contagious fungal skin infection that can affect horses of all ages.  Younger horses are more sensitive than order horse, particularly those maintained under stressful conditions.  Spores of various fungal species can exist in the environment for extended periods of time; they are remarkably resistant to environmental destruction.   Most cases are observed in the cool winter months, when horses are confined indoors and are groomed extensively.   Outbreaks may also occur at times of warm wet weather, a superior time for fungal sporulation on growth.
Infection is dependent upon live spores and skin abrasion, in some cases following very mild skin trauma.  For this reason most lesions occur in the girth or saddle friction areas.
Early signs appear as hairs that stand up off of the skin surface.  Hair loss occurs easily at this time and commonly appears as a round area of hair loss.  Hair loss occurs in a expanding region with the borders becoming diffuse and ill defined.  The girth, neck  and shoulder / chest wall are common sites for infection to occur.  Generalized infection is not common, but may develop in a young horse that is under severe stress or illness.
The horse will only appear to be itchy on the lesions early in the course of disease (first few days).  As the affected area begins to heal hair loss will persist on the outer portion of the affected area, while hair growth will occur centrally in the affected area.
The diagnosis of fungal skin infection is made by microscopic evaluation that reveals the presence of fungal organisms and fungal culture.
Management of horses suffering from fungal skin infection usually involves exposure to sunlight and good nursing care, reduced stress, and maintaining excellent nutrition and proper deworming.  Recovery occurs over a period of approximately 2 weeks.  Specific treatment is aimed at controlling infection in the individual horse as well as controlling infection in the environment.  Clipping affected areas in horses with long hair coats is recommended.  Thorough cleaning of clipper blades is required after use on infected horses.  Topical administration with an antifungal product containing miconazole is typically effective.  All horses in contact with the infected individual and equipment should be monitored for evidence of disease and considered exposed.  Exposure to sunlight of other infected horses is necessary as well.  Topical cleansing of affected areas with an iodine scrub or 2.5% lime sulfur will also aid in control of the spread of lesions.  Oral treatment with antifungal agents should be considered in severe cases that don’t respond to local treatment.  Systemic treatment of such cases will require veterinary consultation and evaluation.
One of the most important aspects of managing fungal skin infection is limiting exposure to other horses in the same environment.  All hair and contact materials should be considered “infected” material and must be properly disposed.  Appropriately diluted  washes of antifungal drugs should be used to clean the environment so that continued or reexposure does not occur.  Horticultural antifungal fumigants can be used for environmental cleaning, but should not be used for topical use.  It is also important to recognize that people can develop lesions from fungal agents and proper protection should be implemented to avoid human infection.  Individuals that do not have normal immune function should not work with horses suffering from fungal skin infection.  
Summary
In summary there are many skin conditions that can affect horses, particularly race horses that are under stressful conditions.  Following good methods of general maintenance and hygiene will reduce the likelihood of lesions developing.  If lesions should occur identification of the type of skin infection will aid in the best course of action for management.  In cases that don’t respond well to initial attempts at management as well as those that progress despite treatment will require veterinary consultation for additional diagnosis and treatment.

Elizabeth G. Davis, DVM, PhD, DACVIM, Kansas State University
 (16 October 2006)

Immunostimulants and their role as an alternative to vaccines

By Elizabeth Davis, DVM
 

What is immunomodulation?  By definition this simply means that we modify the natural immune response.  This can occur in one of two ways, either by boosting the response with immunostimulants or suppressing the response with medications like corticosteroids.  Currently immunostimulation has become a more widely discussed method of managing horses suffering from infectious disease. 

An ideal situation when a host is exposed to pathogen challenge (e.g. bacteria or virus) is to have optimal immunity that protects the host from disease.  However, if we have a situation of overwhelming challenge or an inadequate immune response then we have an individual that succumbs to infectious disease.  In many cases specific therapy in the form of antibacterial, antiprotozoal, antiparasitic or antifungal therapy will work in combination with the immune system to aid with pathogen clearance.  In some instances though, the addition of an immunostimulant will aid in “boosting” the immune response so that we have a more robust immune response acting in coordination with the antimicrobial drug to clear the infection.  Some examples of instances where immunostimulant therapy have been shown to be of benefit to equine patients include prevention of disease prior to stress such as long distance transport or weaning, bacterial respiratory disease, endometritis (infection of the lining of the uterus) or improvement of nasal secretions associated with viral respiratory disease (Equine Herpes Virus, EHV).  When a person is asking whether this type of treatment is right for their horse, it is important to consult with a veterinary professional to determine the appropriateness of such therapy.

Specific examples of diseases
Respiratory infection (prophylaxis and treatment)

Immunostimulants may be beneficial for treatment of chronic, infectious pulmonary disease in young horses.  An example would be a horse that has experienced clinical disease for several weeks with incomplete resolution following antibacterial therapy.  The indications for immunostimulant therapy in horses are relatively specific for the management of infectious disease.  The mechanism of action of nonspecific immunostimulation is activation of specific white blood cells that produce proteins of inflammation called cytokines.  Immunostimulant therapy may not be effective in patients with acute, fulminate infections because the immune response is likely maximally stimulated by the infectious agent.  Therefore, these agents are useful as a preventative therapy or for chronic respiratory infection that is incompletely resolved.  Horses with primary immunodeficiency syndromes, such as severe combined immunodeficiency syndrome of Arabian foals, are incapable of responding to immunostimulant therapy.  Immunostimulant therapy is indicated in horses with chronic bacterial or viral respiratory infections due to immunosuppression or immunotolerance to the organism.  Prophylactic administration of immunostimulant preparations prior to stressful events such as weaning or long-distance transportation may decrease onset of infectious disease that is associated with reduced immune responses and stress.

Propionibacterium acnes:

In equine medicine, Propionibacterium acnes (EqStimÒ, Neogen Inc.)  is recommended for treatment of chronic, infectious respiratory disease that is unresponsive to conventional antibiotic treatment. In addition, it is recommended for prophylactic administration prior to stressful events that may impair pulmonary defense mechanisms, including weaning and long-distance transport.  Propionibacterium acnes is considered an additive (adjunct) treatment to antibiotic therapy, not a stand alone treatment.  Treatment requires a series of 3 injections over a period of approximately 1 week.
In addition to equine respiratory disease, P. acnes has been recommended for treatment of endometritis, osteomyelitis, papillomatosis (warts), abdominal abscess, fistulous withers, and sarcoid skin tumors.  In this author’s experience, administration of P. acnes is effective for treatment of viral papillomatosis, whereas, efficacy for treatment of sarcoid skin tumors (intralesional and intravenous) is less consistent.   
 


Inactivated Parapoxvirus ovis:

Parpoxvirus ovis (Zylexis™, Pfizer Animal Health) is a non-specific immunomodulator that contains a purified highly concentrated viral strain that is inactivated and packaged in a freeze dried form.  In a respiratory challenge model of equine herpesvirus (EHV) infection, Zylexis™ was shown to reduce the severity of nasal discharge when compared with placebo-treated horses.  The response of this treatment occurs rapidly after treatment and may be effective in less than 24 hours.  Similar to other compounds Zylexis™ treatment requires a series of 3 treatments over approximately 10 days.
Respiratory disease and beyond

Interferon-alpha:

Interferon-alpha (IFN) is a naturally produced protein that has antiviral activity.  Interferon production occurs naturally in all mammalian hosts, including horses.  Synthesis of this protein is induced by viral infection, and is an early, nonspecific antiviral defense mechanism.  Interferon-alpha aids with nonspecific immunity via enhanced killing activity of several types of white blood cells.  Interferon- induces an antiviral state in target host cells by stimulating production of enzymes that inhibit viral protein synthesis and degrade viral RNA.  In mice, administration of IFN stimulates white blood cells to produce other proteins that activate the cell response that promotes cellular killing and removal of microorganisms.     


  
Interferon alpha can be used in a few different ways, by the mouth in low doses or systemically at higher doses.  When the low doses are used by mouth the effects include: reduced inflammation in the lower respiratory tract of racehorses with pulmonary inflammation. This treatment reduces fluid and mucous in the respiratory tract, lowers total cell counts in lung fluid therby improving pulmonary health which may improve athletic performance.  Interferon- administration is not effective with all airway conditions, so it is important to visit with your veterinarian to determine what tests are needed and if this therapy is right for your horse.
When IFN is given to the patient by the oral route an interesting effect is that it is not absorbed by the intestine, which is in contrast to many drugs that we administer to our equine patients.  We know this because IFN is degraded by digestive enzymes and cannot be detected in peripheral blood after oral administration.  Instead, oral dosing activates unique natural defense systems originating in the oral cavity (mouth).  This anatomic region is a special component of the immune system called the oropharangeal-associated lymphoid tissue. White blood cells exposed to IFN transfer enhanced biologic effects to other naive white blood cells in the absence of IFN.  Ultimately this therapy has a bit of a domino-effect from one activated white blood cell to another.  This process requires direct cell-to cell-contact, which does not require continued presence of IFN.  Cell-to-cell transfer of the antiviral state to naive cells permits low to undetectable concentrations of IFN to produce potent antiviral activity, and possibly represents a major mechanism for amplification natural IFN activity.  White blood cells then enter general circulation and communicate this antiviral capability to cells at distant sites.  This mechanism allows the biologic effects of IFN to reach tissues accessible to mobile white blood cells, in which penetration of IFN is poor, such as the surface of the respiratory tract, gastrointestinal tract, and eye.

Although this treatment is effective under various conditions, it is important to note that patients can become unresponsive to IFN therapy after repeated administration due to production of anti-IFN antibody (protein) or reduction in sensitivity of the immune system to the interferon that is given. These effects occur after the host has been exposed to a foreign protein (in this case IFN-α) several times.  The effect of antibody production that limits the effectiveness of IFN has been observed in human patients and calves.

An additional use of interferon-α is a larger dose administration given systemically (intravensously).  When used in high doses, this treatment can be beneficial for horses suffering from certain viral diseases, such as West Nile Virus encephalitis.  Since we don’t have an effective antiviral drug for treatment of WNV, the use of a natural protein made by the immune system makes good sense.  In the cases that have been managed with this therapy, the results have generally been favorable.   
  
Additional uses of immunstimulant agents including equine endometritis

Mycobacterium:

Mycobacterial products have long been recognized as potent stimulators of nonspecific immunity.  The bacteria Calmette-Guerin (BCG) vaccine was developed from a strain of Mycobacterium bovis that had been inactivated through serial passage (growth) in culture. Live BCG, whole-inactivated BCG, and mycobacterial cell wall fractions have been used as nonspecific immunostimulant agents, and all 3 preparations demonstrate strong activity when administered with antigen.  The mechanism of action is white blood cell activation and subsequent release of immune stimulating proteins by the host, called cytokines.  Whole, inactivated BCG preparations can be highly reactive; therefore, partial cell wall products have been developed that are less reactive.  Purified peptides (tiny proteins) are the smallest subunit of the mycobacterial cell wall that maintains immunostimulant activity.  In equine medicine, mycobacterial cell wall products are used to treat infectious respiratory disease (Equimune IVÒ, Bioniche, Belleville, ON, K8N 5J2) and sarcoid skin tumors (RegressinÒ, Bioniche, Belleville, ON, K8N 5J2).

Purified mycobacterial cell wall extract is labeled for single-dose, intravenous administration, as solo therapy for treatment of equine herpesvirus infection.  Administration of purified mycobacterial cell wall extract improves clinical recovery of horses with respiratory disease resulting from stress, transportation, bacteria and/or viral infections.  In an investigation looking at the efficacy of such preparations response to treatment was determined by monitoring clinical signs (fever, cough, anorexia, nasal discharge, abnormal auscultation, poor performance) and laboratory tests (complete blood count, differential, and acute phase protein concentration).  More than half of the horses treated with mycobacterial cell wall extract improved significantly within approximately a week after administration of a single dose, whereas less than half of the saline treatment group were without clinical signs.

In human medicine, live BCG immunotherapy is used for treatment of certain tumors that affect the urinary system.  In such patients, treatment with live BCG organisms prevents recurrence or progression of superficial bladder tumors, and the response is superior to treatment with certain chemotherapeutic agents.  Complications may occur in patients that are treated multiple times with a certain BCG products, veterinary consultation will help avoiding complications with administration.

Mycobacterial cell wall extract

Settle® (Bioniche, Belleville, ON, K8N 5J2) has been studied for its effectiveness to treat endometritis in mares.  Endometritis is classified as an infection of the innermost lining of the uterus.  In certain mares, persistent infection of the uterus may impair reproductive soundness, so clearance of infection is an important mechanism to maintain reproductive health in infected mares.  The most common bacterial pathogen associated with endometritis in horses is Streptococcus zooepidemicus.  Settle has been shown to work well alone and in combination with standard therapies to clear infection of the uterine lining.  This product can be used as a systemic treatment (intravenously) or locally (in the utuerus).  Consultation with your veterinarian will help determine if this therapy is right for your mare.

Conclusion

Immunostimulant therapy may be beneficial for equine patients under a variety of settings that include prevention and treatment of various infectious diseases.  It is important to know the appropriate use of such treatments so that the ideal immunostimulant preparation is selected for each individual patient. Determination of the factors of disease in your horse will be provided by appropriate veterinary evaluation.  In some instances this method of treatment will work in combination with antimicrobial agents to enhance the clearance of pathogen challenge.    
 

Osteochondritis dissecans - the development, causes and treatments of OCD

By Deborah Spike-Pierce, DVM
​

One of the most common orthopedic problems encountered in young horses is osteochondritis dissecans (OCD).  This is of particular concern in the Thoroughbred industry, where horses are often bought and sold before maturation is complete and are expected to perform starting at a relatively young age.  There are many common sources of confusion surrounding this disease.  Deborah Spike-Pierce, DVM discusses research into the development, causes and treatment of OCD.

Development

In the most basic sense, OCD is caused by a disruption of the normal growth process of bone. It most commonly occurs in young fast growing animals such as large breed dogs, pigs and horses.  Normally, a cartilage framework in the growth plate at the end of a bone is slowly converted into bone as an animal grows.  If this ossification process is interrupted, the syndrome of OCD can result. There are three major stages of this disease, although the term OCD is commonly used to refer to all parts of the syndrome.  The first phase is osteochondrosis (OC), which is a disturbance of ossification of cartilage into bone resulting in excess retained cartilage.  If this retained cartilage results in inflammation of the joint, this stage is termed osteochondritis.  The inflammation may manifest itself clinically as joint distention or lameness.  Osteochondritis dissecans (OCD) is the stage where a portion of the retained cartilage loosens from the parent bone and forms a fragment.  The separated fragment may remain cartilage or it may ossify into bone.  It is the disturbance of this fragment that can cause the most severe clinical form of the disease by shedding debris into the joint, thus causing synovial effusion and lameness.  Not all horses that develop OC will go on to develop OCD.  In many cases, horses will have no clinical signs and areas of retained cartilage will go on to ossify normally as the horses grow with no long term consequences.

Many different parameters have been described as having an affect on the development of OCD. There is no apparent common denominator in OCD formation and the disease is multifactorial.  Nutritional imbalances, trauma, rate of growth, biomechanical influences as well as genetic predisposition have all been documented as potential causes.

Recent research on the relationship between nutrition and development of OCD have found multiple correlations.  It has been shown recently in the United States that the time of year can affect OCD rates due to spring and autumn peaks in the energy content of the grass.  In studies, horses fed diets with low copper, excess zinc, excess phosphorus and high digestable energy have all shown increased rates of OCD.  There has been an emphasis placed on copper intake, especially in pregnant mares, as copper has been shown to play an important role in the repair of osteochondrotic lesions.  Since mineral content of feed and forage vary throughout the world it is recommended to concentrate on a sound nutritional program since the nutritional contribution to OCD formation itself is multifactorial.

Certain sites in each joint are predisposed for OCD formation.  It is thought that a high mechanical load in areas of thickened cartilage where the blood supply is tenuous can lead to OCD due to traumatic causes.  Conformation may play a role in the distribution of the weight that the horse places on the developing bone.   It has been proposed that horses with a toe-out and upright conformation of their hindlimbs may have higher levels of hock OCDs.  This issue is intertwined with genetics as conformation is influenced by genetics.  Conformational variations can also induce more mechanical stress in particular areas and affect the ossification process via trauma.

Research investigating a possible link between genetics and OCD development is ongoing.  Studies in Standardbreds assessing the prevalence of hock OC have shown heritability rates ranging from 0.25 to 0.52.  These numbers appear significant, however certain warmblood studbooks will not allow stallions with hock OCD into their registry and after 20 years the incidence within the breed has not decreased.  This again supports the claim that OCD is a multifactoral disease.The most recent research on OCD development is at the molecular level.  The focus is on the development and maturation of cartilage, growth factors, collagen types and the expression and metabolism of these factors in bone development.

Osteochondritis dissecans can occur in many different joints but is most commonly identified in fetlocks, hocks and stifles.  Generally, the fetlocks are the first joints affected, followed by hocks, where OCD develops between 2-6 months of age.  OCD of the stifle and shoulder joints usually emerges later, often between 6-9 months of age.  In short, the larger the joint or the longer it takes to ossify, the later OCD develops.  These are the typical windows of susceptibility but since OCD may be traumatic as well as purely developmental in nature the disease may manifest itself at a later time.

Clinical Signs

In many cases, OC and OCD may be clinically silent, with no outward signs that a problem is occurring.  In other cases, there are outward manifestations of the disease.  Fetlock OCD may present as a foal or weanling with persistent distention of one or more fetlocks, with or without lameness.  Radiographs of the affected joints may confirm an OCD lesion.  However, traumatic chip fractures of P1 and sesamoid bone fractures present with similar clinical signs, so radiographs may show those lesions instead.

 
A foal or weanling with hock distention (bog) with or without lameness may also have OCD.  Hock OCD is often bilateral, even if distention is only present in one leg.  High quality radiographs are essential in this diagnosis, since small lesions may cause significant joint distention.

Stifle OCD can have a slightly different presentation, often found in a lame yearling with stifle distention.  Radiographs taken at the onset of the lameness and joint effusion may not show an OC or OCD lesion; it may require several weeks for the lesion to be evident radiographically.  However, even without radiographic evidence of a lesion at the onset of the problem, it is important to restrict exercise because the joint debris causing the effusion may result in significant damage to the articular cartilage with excessive exercise.

Diagnosis

A diagnosis of OC or OCD is most often made from radiographs.  OC lesions are characterized by a lucent area in the bone representing an area of retained cartilage.  OCD lesions often have a similar lucent area as well as the presence of a bony fragment.  However, some lesions are not able to be identified on radiographs and exploratory arthroscopy may be necessary to make the proper diagnosis.

Osteochondrosis lesions occur in specific anatomic sites in horses.  In a stifle, OCD lesions most commonly occur in the lateral trochlear ridge of the distal femur (Figure 1), the medial trochlear ridge of the distal femur and less commonly in the patella.  The most common area of OCD in the hock is the distal intermediate ridge of the tibia (Figure 2), followed by the distal lateral trochlear ridge of the talus and the medial malleolus of the distal tibia.  Fetlock OCD most commonly occurs in the proximal (Figure 3) and distal sagittal ridge of the distal cannon bones.

Since Thoroughbreds are sold at ages ranging from a few months old to adulthood, many variations of this syndrome are seen on survey radiographs.  In young horses, a lucency is often seen where the cartilage in this location has not fully ossified.  Many of these areas  will continue to ossify as the horse matures and not develop OCD.  However, some will go on to develop OCD. This is a grey area purchasers face when buying immature horses.

Treatment

Since there is not a preventive solution for OCD, horses with this disease often need to be treated.  This usually consists of either conservative medical management or arthroscopic surgery.  Conservative medical management has been shown to be successful in very young horses that still have the capacity to heal an OC or OCD lesion.  Regimes may include a modified exercise program, medication, and supportive therapy.  Exercise modification may involve reducing the intensity and amount of exercise (changing from large field to small paddock turnout, for example) or it may be as drastic as stall rest in severe clinical cases.  Medications focus on improving the health of the joint, decreasing inflammation, and augmenting the blood flow to the area of OC or OCD.  Supportive therapy can be as simple as bandaging an effused joint.

If a lesion is non-responsive to conservative management it may need surgical intervention. Surgical treatment is generally the treatment of choice in true OCD lesions that have a flap (versus the OC lesions that characterize the initial phase of this disease).  Surgery is recommended in these types of lesions even if the horse is not showing clinical signs.  It is likely that a true OCD lesion visible on radiographs will become a clinical problem in training and thus require down time for surgical treatment during the training or racing process.  Therefore, it is best removed before the joint is inflamed and further damage occurs.  Prognosis varies by joint but is generally favorable, except in the case of the shoulder joint.

In a study of Thoroughbreds with stifle OCD affecting the femoropatellar joint the affected horses’ overall racing performance was not significantly different than their unaffected siblings.  Fewer of these horses started races at two years old, but there was no difference at three years of age.  The size of a stifle lesion can be a concern when a horse is marketed; however no study has been able to link the size of the lesion with performance.  It is also important to note that the radiographic size of an OCD is not always consistent with the true size identified at surgery because a portion of the OCD is cartilaginous and therefore not identifiable radiographically. 
A study of hock OCD in Thoroughbreds and Standardbreds who underwent arthroscopic removal of the OCD lesion showed the overall racing performance was not different between affected horses and their siblings. The site of the lesion also had no impact in  performance.

There has not been a study published assessing racing performace in horses with fetlock OCD lesions.  However, studies involving multiple breeds show favorable results from surgery.  Ninety perfect of horses who had proximal sagittal ridge OCD lesions arthroscopically debrided returned to athletic activity.

Conclusion
Osteochondritis dissecans can be a confusing and concerning disease.  Although research into its causes is ongoing, there are many effective treatment options available.  Many lesions will heal without requiring surgical intervention and the prognosis for those requiring surgery is generally favorable as well.

Reiki - Paul Peacock discovers the ancient Japanese healing method.

Many racing yards are turning to a number of alternative treatments in an attempt to either speed healing times, improve the life styles of individual thoroughbreds or respond to the wishes of owners who themselves have clear ideas and requirements for the care of their animals. A fast growing treatment for racehorses is Reiki, an ancient Japanese healing methodology which is said to date back over 2000 years, but was actually ‘discovered’ by a monk in Victorian times. It involved a combination of Japanese and Christian philosophies – the manipulation of Chi and the laying on of hands.

Only recently has this technique been used with animals, possibly most successfully on equines. Trainers frequently try Reiki for a halting and infrequent period, and there are two reasons for this, according to Beth Luck, an equine Reiki therapist. “If substantial treatment with Reiki takes place, and is successful, the horse can become calmer and in some circumstances loose that winning instinct – it becomes a horse again.” The last words a trainer needs to hear is that a racehorse somehow calms itself in a racing sense. The second reason is the unbelief that the fundamentals behind the process actually work. But there are reasons why, in certain circumstances, thoroughbreds might benefit from the attention of someone trained, or attuned, to Reiki in a racing yard. As we shall see later, Reiki is associated with a calming effect on an agitated animal, and the greatest successes have been achieved where the thoroughbred has become difficult to ride, or is confined to box rest or shows signs of agitation.

It is a source of frustration often repeated by practitioners that they believe an animal needs more attention and or rest than might be actually available in a racing schedule, and consequently the patient is being only partially accommodated and frequently returned to racing too quickly. It would be easy to see that an animal only partially well would fall to injury in training or on the track. But then are the claims of Reiki practitioners valid, after all, every athlete, human or equine will benefit from a lot of rest and attention? Reiki is thought to be connected to the body's magnetic or energy field. Some people say it is the manipulation of the Universal Life Energy and that the ‘patient’ receives energy through the practitioner which puts things right. This energy is sometimes referred to as ‘chi’ and is the same as that which is manipulated by acupuncturists and Oriental massage practitioners.

This is the same so-called energy system as that used in Yoga and other oriental healing techniques. The basic idea is that the energy pervades all living things and is needed in order to put your system in the best possible status so that you can heal yourself. There is said to be a difference between the Reiki energy and all the others forms of chi; it is described as ‘beautiful energy’. The more a practitioner delves into the process the more beauty he or she is said to recognise in the energy. All the other forms of chi are cold in comparison. In Reiki this energy can be received by the laying on of hands or the near contact; the hand being waved or held just above a special point.

Thus the patient can ‘drink in’ energy which allows the body to heal itself. The ‘special points’ are known as Chakras, and the animal is supposed to let the person know which, if any, can be used. It is also important for practitioners to make sure the animal is happy before any administration. The crown Chakra is between the ears and another, called the third eye, just above the line of the eyes. There is another by the throat and yet another by the withers and there is a solar plexus Chakra and a sacral one, with a root one by the rump. Interestingly, all these points happen to be largely where the animal’s centres of lymph nodes. All these points are used by the practitioner, and the training the Reiki practitioner undertakes involves an appreciation of which channel is actually accepting the energy.

The idea of there being an energy involved in the healing process should imply that the animal actually feels something. There are reports of exactly that among people who are able to report their responses. Warmth and tingling are frequently reported during sessions, but there are few if any scientific studies that measure either a temperature rise in tissues or an increased blood flow where the sensation is being reported. Various claims are made for this treatment in humans from the healing of cancers to tempering of moods, and there is a wealth of circumstantial evidence to show the treatment has been to good effect.

But there are equally a large number of claims of fantastic results with horses, particularly where the animal has suffered some trauma or other. The use the non scientific term, ‘puts things right’ about best describes the process of what practitioners believe the ‘energy’ is actually doing. Some practitioners call this chi a spiritual energy to differentiate it from heat or kinetic energy. In short, the energy is said to be something all animals need, but is not measurable in standard scientific terms. Consequently, some practitioners are able to provide treatments from a very great distance, the conduit for this energy being some form of spiritual communication. Simon Earle, who practices what he calls natural horsemanship, had a Reiki practitioner in the yard for some time who worked on the horses, but the results were not discernibly different from the other work in the yard. Lisa Venables of Holistic Horses has used a modified form of Reiki in her yard where animals have been discarded from the racing scene.

She uses a number of techniques, but has an interesting take on Reiki which retains the energetic theory, but could provide an insight into the therapeutic effect of the treatment. She believes that we communicate our state of excitement to horses and the action of Reiki is basically calming. In order to be able to do it in the first place, the practitioner has to be confident and calm, and this is communicated to the animal. A horse that has a problem, and suffers from the stress of the injury or illness and also the stresses of living in a fast paced, modern racing yard, might not heal as well as it could.

The Venables version of Reiki involves bringing the animal to a relaxed state, and once relaxed and at peace, healing has more of a chance of success. This communication of the human’s calm, she believes is an energetic process. This is more likely to mean a proactive understanding between the animal and the human, responding on feedback from the other, and emotional rather than spiritual in essence. This empathetic idea of Reiki is certainly more understandable to Western minds and yet still draws on resources or perception and communication that might be considered ‘alternative’ by many.

The kind of person who is able to communicate in this way might not fit in to the life of modern racing stables, with the fast paced sequence of training and therapies. However, Lisa believes every yard should have one person on the staff able to “communicate” with the animals in such a way. The law regarding Reiki is the same as any complimentary therapy in that it must not be used as frontline treatment. It is an offence not to allow a suitably qualified vet to treat any ailment or injury the animal might develop. It is similarly an offence to diagnose a problem or propose a course of treatment. In short, Reiki can only be administered as an adjunct to treatment, under the supervision of a vet.

The vet is within his remit of care to refuse to allow Reiki, or any complimentary therapy, where he believes it might be injurious to the animal. This might happen, for example, when the practitioner waves his or her arms around a lot and consequently unnerves the animal. There do exist, however, horse therapy centres where, like the one run in Wicklow, Ireland by Heidi & Philip Sheane, who has an equine vet on site and a mix of complimentary and conventional healing takes place. Reiki is a part of the compliment of therapies and a horse has a tailored programme to match its own needs. Reiki is practised by a few equine practitioners around Chantilly in much the same way around the UK.

It is of most interest in America, where there is a well established, if loose, association of practitioners. The laws covering the use of Reiki in the UK are set in Equine and Animal husbandry EU statutes, and similar ones exist in the USA. However, there are no uniform practitioner training requirements and almost anyone can set themselves up as a Reiki practitioner. Whether you believe in the Chi energy transfer explanation for the apparent success of this technique or whether you feel there are other explanations including the setting of an animal at ease and reducing stress will determine which kind of person you employ, if any. A Reiki practitioner with a comprehensive racing yard understanding can provide an angle to animal care which will benefit both horse and owner.

A part of the technique is to notice the response of the animal when they are laying on hands and can therefore understand which parts of the animal are ‘taking the healing’. Such feedback has proved effective in assessing day to day practicalities of training such as poorly fitting saddles, rider stance and shoe problems. Certainly there is mileage in improving horse health by paying them long term physical attention; everyone associated with them will know how much racehorses crave it, and Reiki is an excellent conduit for making a horse feel special. Whether it is the impulsive impartation of healing energy remains to be seen.

Equine Gastric Ulcer Syndrome

Vets and other professionals recognise that gastrointestinal function and health in horses exists in a finely balanced state. Most conditions relating to the intestinal tract, for example colic and diarrhoea are well understood and are most commonly treated either medically or surgically. There has been, however, less appreciation of how frequently the health of a horse’s stomach can be compromised. The true prevalence of equine stomach lesions (gastric ulcers) was recognised only with the introduction of gastric endoscopy. How prevalent are ulcers? Numerous studies conducted in the 1980s and ‘90s in varied horse populations within differing sporting disciplines identified EGUS as a much more a widespread problem than commonly assumed. Many of these studies focussed on thoroughbred racehorses, and produced remarkably similar findings.

Between 80 and 90% of horses in training were found to have gastric ulcers. And, somewhat surprisingly, over 50% of racehorses temporarily out of training also had lesions. Moreover, this health and welfare issue was not confined to thoroughbred racing; horses competing in other equestrian sporting disciplines were also prone to this condition. In contrast, less than 5% of permanently grazed horses appear to suffer from gastric ulceration. Prevalence of EGUS in horses engaged in different equestrian sporting disciplines Population Prevalence (%) Racing (thoroughbreds) 80 - 90 Trotting/pacing (standardbreds) 72 - 88 Endurance racing 67 Show horses 58 Foals (thoroughbred) > 50 Symptoms to look for that may suggest gastric ulceration include chronic recurrent colic, episodic colic, acute colic, reduced appetite, poor body condition and chronic diarrhoea. Whilst these clinical signs are not always indicative of gastric ulcers, as can be seen from the table below there is a clear relationship.

The strongest indicator appears to be an inability to thrive as indicated by poor body condition and reduced appetite. Incidence of overt clinical signs in horses subsequently found to have EGUS Clinical signs Incidence (%) Chronic recurrent colic, for 7 days or more 25 Episodic colic (1+) for 7 or more days 13 Acute colic 10 Reduced appetite 53 Poor body condition 40 Diarrhoea 9 Unfortunately, however, in about 52% of horses where gastroscopy reveals ulceration there will have been no obvious prior clinical signs.

What causes gastric ulcers? Gastric lesions (ulcers) are now recognised as a common condition in stabled horses, whether involved in racing or other equine sports, and in foals, yet they appear to be absent in wild horses. You may be familiar with the fact that gastric ulcers in humans are frequently caused by infection with a bacterium called Helicobacter pylori, it was not surprising therefore that this was investigated but then dismissed as a possible cause in horses. So, what is the cause and why is the prevalence in racehorses so high? To answer this question we need to examine the manner in which we train, house and feed our racehorses. All the clinical evidence to date indicates that the high incidence of gastric ulcers in racehorses is a ‘man-made’ phenomenon that is related to the feeding and management practices that we employ during training.

There are four key contributory factors involved in the development and progression of ulcers:

1) Dietary makeup and feeding practices

2) Intensity of exercise (level of work)

3) Stress factors

4) Prolonged use of non-steroidal antiinflammatory drugs, such as phenylbutazone, and corticosteroids. When considering these factors we need to appreciate that the horse has evolved over millennia as an exclusively grazing animal with a digestive system that is reliant on the continual ingestion of fresh forage to meet its dietary requirements. In EGUS the damage caused to the lining of the stomach arises from prolonged exposure of the gastric mucosa to gastric acid, without sufficient protection from the buffering effect of saliva.

Dietary makeup and feeding practices Racehorses are most often fed a diet that is high in starch rich cereal and low in forage. Horses produce gastric acid continuously, and high starch diets tend to further increase its production through stimulation of a hormone known as gastrin. In addition, where these starch-rich meals are large, inadequate mixing in the stomach can lead to some of the starch being fermented here, which further contributes to the overall acidity. During feeding, chewing normally stimulates the production of saliva, which contains a natural buffer ‘bicarbonate’, to offer some protection of the gastric mucosa against the corrosive effects of gastric acid. However, the amount of saliva produced for each kilogram of concentrate feed consumed is about 2.5 times less than that produced for the same weight of forage, as proportionally less chewing is involved. Minimal forage intake therefore takes its toll on gastric health, as during periods when the horse has no access to feed or forage, the protective effects of saliva are lost and these are key danger times for gastric ulceration.

A recent study published in the Equine Veterinary Journal also suggests that repeated electrolyte or salt administration may exacerbate or even induce gastric ulceration. But before we all cast aside our daily electrolyte or salt administration, which has great physiological benefit, we need to take these recent findings in context. This latest study used an endurance model of electrolyte administration using a concentrated electrolyte syringe 8 times within an 8-hour period. Whilst this may be common practice during endurance races, this type of administration in racing is in my experience not practised. It is, however, a difficult conundrum for endurance trainers as electrolyte depletion during races is a significant issue.

Certainly electrolyte or salt products that dissolve more slowly in the stomach may be an advantage. Exercise intensity The level of work that horses undertake has also been found to be a significant contributory factor in the development of EGUS. Although ulcers are present in about 40% of horses undertaking light exercise this increases to over 95% in horses with busy racing schedules. This effect probably arises through the physical movement of the organs and tissues within the horse’s body that occurs during exercise. Mechanical movement and compression of the stomach forces the most sensitive non glandular regions of its lining into further contact with gastric acid, and this effect is exacerbated when exercise intensity is increased.

Stress Although training and racing by necessity place horses under physiological stress, psychological stress is also implicated in ulcer development. Recent studies in the USA indicate that sudden stressful changes from the normal daily routine and environment, including transport and new stabling, promote rapid changes to the integrity of the stomach lining. Indeed, gastroscopy showed the appearance of ulcers within only 6 days. Medical treatment of gastric ulcers Gastric ulcers in horses rarely heal spontaneously, so veterinary intervention is necessary. Methods for the treatment and prevention of gastric ulcers in horses follow those employed in human medicine and generally involve the use of antacids alone, or in conjunction with anti-ulcer drugs.

Antacids neutralise gastric acid. Those based on sodium and calcium carbonates and bicarbonates have the potential drawback of releasing carbon dioxide (gas) in the gut. In addition, bicarbonate supplementation can increase blood bicarbonate levels that could potentially result in a breach of doping rules. Antacids containing aluminium or magnesium hydroxides and silicates may be preferential.

Drugs used to inhibit gastric ulcers include, the H2-receptor blockers cimetidine and ranitidine and the so-called ‘proton-pump inhibitor’ omeprazole. Omeprazole is the most widely used and effective treatment in horses and is marketed as an oral paste under the trade name Gastroguard. Dietary supplement products available for gastric health Product Company Active ingredients Function Product Form Dose (500kg horse) Neigh-Lox Saracen (KER) Dihydroxy-aluminium, sodium carbonate, calcium carbonate, aluminium phosphate Antacid Coats & protects Pellet 340g Settlelex Feedmark Calcium carbonate, aluminium hydroxide, magnesium carbonate, dicalcium phospahte Antacid Powder 30-100g Acti-Soothe Nelson Veterinary Ltd high fibre ingredients, calcium carbonate. Magnesium carbonate, probiotic, prebiotic Antacid Pellet 400g Gastro Ardmore Equine phytochemicals, mucosal agents,, natural antibiotics, natural stress reducers Other Paste 1 syringe Ulseraze NAF Powder, lactoferrin, ginger, marshmallow, Liquorice,psyllium seeds, phosphotidylcholine, Other Powder 60g U-Guard Equine America Calcium carbonate, kaolin, liquorice, aloe Vera, iron oxide, dried apple pectin pulp, magnesium silicate, vitamin B5 and magnesium oxide. Antacid Coats & protects Powder 40g Stomacare Twydil polyunsaturated fatty acids, phospholipds, chitosan glucosamine fibre Antacid Coats & protects Syringe 1-2 syringes (60-120g) Dietary prevention of ulceration Mark Tompkins chairman of the Newmarket Trainers Federations takes the view that “a common sense approach to gastric ulcers is what's needed, with care being taken over the feeding regime and any stress on horses being kept to a minimum”. In essence he is absolutely correct and as we largely know what the dietary trigger factors are, this should be a fairly straightforward process.

Firstly, whilst the need to minimise gut fill from forage is appreciated, we should try to maximise forage intake whenever possible. This serves two purposes by increasing the amount of protective saliva produced, but also reducing the amount of time that horses in training spend without access to feed. Racehorses could benefit from the best of both worlds, if they were fed more hay or haylage for the majority of the time, with the level being reduced to a minimum (1% of bodyweight for hay and 1.25% of bodyweight for haylage) in the 2-3 days before racing. Additionally, any horses that suffer from recurrent ulcers would certainly benefit from turnout onto pasture for some part of the day. Ensuring meal size is minimised can mollify the negative effects of a high cereal intake. Greater number of small meals, rather than a few large ones is the better option.

It is usually the second and third meals of the day that often need to be reduced and be redistributed to a fourth late feed. Addition of generous double handful of alfalfa chaff to concentrate feeds will also encourage chewing and improve saliva production. Supplements fed to help maintain gastric mucosal health are unlikely to be as effective as drug treatments such as Omeprazole. However, they can be used as an adjunct to veterinary therapy following an initial course of treatment, or during periods where drug treatment has to be withdrawn to avoid contravening doping regulations. In choosing a product however, selecting those from companies that have tested the efficacy of their product in a scientific environment is a wise strategy.

Electrolyte Balance – vital to the proper functioning of a racehorse's system

Electrolytes are essential components of the racehorse’s diet as they are vital to the proper functioning of the body’s basic physiological processes, such as nerve conduction, muscle contraction, fluid balance and skeletal integrity. The major electrolytes, sodium, potassium, chloride, calcium and magnesium are widely distributed within the body, but can be more concentrated in particular organs and tissues. For example, the level of potassium is very high in red blood cells but quite low in plasma, and the level of calcium in blood is low, but comparatively very high in bone and in muscle cells. The body has in-built mechanisms that work to maintain the correct electrolyte balance within the tissues, fluids and cells. These modify the absorption of electrolytes in the gut, or their excretion by the kidneys. These mechanisms are not foolproof however, and electrolyte loss through sweat can be a major issue for Thoroughbreds. The sweat of the equine athlete, unlike its human counterpart, is hypertonic; meaning that horse sweat contains higher levels of electrolytes than the circulating blood plasma. Consequently, the horse loses comparatively large quantities of electrolytes through sweating.

Although the electrolyte composition of equine sweat varies between individuals, on average a litre would contain about 3.5g of sodium, 6g of chloride, 1.2g of potassium and 0.1g of calcium. From this we can see that the majority of the electrolyte lost is in the form of sodium and chloride or ‘salt’. The amount of sweat produced on a daily basis and therefore the quantity of electrolytes lost differs from horse to horse and depends on a number of factors. As sweating is primarily a cooling mechanism, how hard a horse is working, i.e. the duration and intensity of exercise and both the temperature and humidity of the environment are all significant. Horses can easily produce 10 litres of sweat per hour when working hard in hot humid conditions. Stressful situations can also cause greatly increased sweating.

For example, during transport horses can lose a significant amount of electrolyte through sweating and the opportunity for replenishing this loss through the diet may be less as feeding frequency is reduced. Use of electrolyte supplements either in the form of powders or pastes is advocated before, during and after travel, especially over long distances. Jim Paltridge from IRT (UK) Ltd, (International Racehorse Transport), says, "we use a powdered electrolyte supplement added to the feed on a regular basis given for the 3 days prior to travel. We find this helps offset much of the loss normally incurred during transport and subsequently the horses arrive at their destination in better shape. We feel this electrolyte supplementation is a valuable attribute in the ongoing battle to reduce in-flight dehydration".

Electrolytes lost from the body in sweat must be replenished through the diet. All feeds, including forages, have a natural electrolyte content and in concentrate feeds this is usually enhanced by the addition of ‘salt’, which is sodium chloride. Forages such as grass, hay, haylage or alfalfa (lucerne) naturally contain a large amount of potassium, as can be seen from the table 1 below. In fact, 5kg of hay for example, would provide in the region of 75g of potassium, which largely meets the potassium needs of a horse in training. It is therefore questionable whether an electrolyte supplement needs to routinely contain very much potassium unless forage intake is low. Calcium is another important electrolyte, but it is lost in sweat in only very small amounts and its availability in the diet tends to be very good.

Calcium is particularly abundant in alfalfa with each kilogram of the forage providing nearly 1.5g of calcium. A kilo of alfalfa alone would therefore go a long way towards replacing the likely calcium loss through sweating. In addition, the calcium found in alfalfa is very ‘available’ to the horse in comparison to other sources, such as limestone. Calcium gluconate is another very available source of calcium, however, it has a relatively low calcium content compared to limestone (9% vs. 38%) and so much more needs to be fed to achieve an equivalent calcium intake. Interestingly, there is great variation between individual horses in their ability to absorb calcium, however, scientific studies carried out at Edinburgh Vet School showed that this variability was considerably less when a natural calcium source in the form of alfalfa was fed.

By far the most important electrolytes to add to the feed are sodium and chloride or ‘salt’. The levels of sodium and chloride found in forage are quite low and due to manufacturing constraints only limited amounts of salt can be added to traditional racing feeds. A typical Racehorse Cube fed at a daily intake of 5kg (11lbs) would provide only about 20g of sodium and 30g of chloride. As can be seen from table 2 this is a fair way short of meeting the daily requirements for these particular electrolytes by a racehorse in hard work.

It is therefore very important that supplemental sodium and chloride is fed. Ordinary table salt is by far the simplest and most economical electrolyte supplement, but the downside is the issue of palatability as the addition of larger quantities of salt to the daily feed can cause problems with horses ‘eating up’. As an alternative salt could be added to the water, but only when a choice of water with and without salt is offered. Salt should not be added to the water if it puts a horse off from drinking, as dehydration will become a problem.

Inadequate water intake can also contribute to impaction colic. Saltlicks are another alternative, although intake can be vary variable and we rely on the horse’s innate ability to realise its own salt requirements, which is questionable. So addition to the feed is by far the best route for adding salt or electrolyte supplements to the diet. Splitting the daily intake between two or three feeds can reduce problems with palatability.

Mixing salt and Lo Salt can make another simple DIY electrolyte supplement in the proportion of for example 500g to 250g respectively. Salt is sodium chloride (NaCl), whilst Lo Salt contains a mixture of sodium chloride and potassium chloride (KCl). This formulation provides 3g of sodium, 6g of chloride and 1g of potassium per 10g measure. This DIY mixture will replace these electrolytes in the approximate proportions that they are lost in sweat. What are the implications of a racehorse’s diet containing too little or too much of an electrolyte and how can we assess this? An inadequate level of certain electrolytes in the diet in some horses may simply result in reduced performance. In other individuals, it can make them more susceptible to conditions such as rhabdomyolysis (tying up), or synchronous diaphragmatic flutter (thumps), both of which are regularly seen in horses in training. Conversely, an excess electrolyte intake is efficiently dealt with by the kidneys and is ultimately removed from the body via the urine.

Therefore, the most obvious effect of an excessive electrolyte intake is increased drinking and urination. For this reason, the use of water buckets rather than automatic drinkers is preferred, as whilst the latter are far more labour efficient, the ability to assess water intake daily is lost. Excessive electrolyte intake can also be a causative factor in diarrhoea and some forms of colic. There is also some recent evidence in the scientific press that suggests that repeated electrolyte supplementation might aggravate gastric ulcers. However, these early studies used an electrolyte administration protocol typical of that seen during endurance racing, rather than simply a daily or twice daily administration, which is more commonly used in racing.

Supplements that contain forms of electrolyte that dissolve more slowly in the stomach, however, may be less aggressive to the sensitive mucosa. Unfortunately blood levels of sodium, potassium, chloride or calcium are poor indicators of whether dietary intake is sufficient or excessive unless it is very severe. This is because the body has effective systems for regulating the levels of these electrolytes in blood within very tight physiological limits. A creatinine clearance test, which measures the electrolyte content of a paired blood and urine sample is a much more useful indicator of dietary electrolyte adequacy.

There are a large number of commercial electrolyte products available, with a wide range in the breadth of ingredients that they contain. Consequently, they vary enormously in the amount of electrolyte that they deliver per recommended daily dose, as can be seen in table 3. In addition, whilst some glucose or other carbohydrate can help improve palatability, its presence should not compromise the amount of electrolyte that is contained within the supplement. In humans, it is recognised that the uptake of sodium from the gut is improved in the presence of glucose, while this effect in horses has not been firmly established. Electrolyte paste products are also often used either before and or after racing or travel.

These products are useful as they allow rapid electrolyte intake even when feed eaten may be reduced following racing. These electrolyte pastes often provide a more concentrated form of supplement and it is extremely important to ensure that the horse has access to water immediately following their use. Failure to do this may mean that the concentration of electrolytes in the gut actually draws water from the circulating blood, which can exacerbate dehydration. Another disadvantage with paste supplements is that if they are not formulated well, with an appropriate consistency, they can be difficult to dispense from a syringe and the horse may also be able to spit most of the product out after administration.

Some simple rules of thumb for choosing a good electrolyte are that salt should be one of the first ingredients listed on pack, as all ingredients are listed in descending order of inclusion. Additionally, be wary of supplements that taste sweet, as they may contain a lot of carbohydrate filler and little electrolyte. Some electrolyte supplements also contain many superfluous ingredients such as vitamins and trace minerals. The inclusion of these latter ingredients is largely unwarranted and their presence could cause issues with oversupply if the electrolyte is multi-dosed daily. Some electrolyte products specifically marketed towards racing may also contain bicarbonate.

The theory behind its inclusion is sound as ‘milk shaking’, whilst outside the rules of racing, has some scientific validity. However, the limited amount of bicarbonate contained in such electrolyte supplements is unlikely to have the positive effect on performance attributed to the former practice. Other extra ingredients such as pre-biotics may be more useful as they may improve the absorption of some electrolytes. In Summary, electrolyte supplementation in one form or another is essential within a racing diet. Ensuring that you are using a good electrolyte supplement is important and the quantities fed must be flexible and respond to changes in the level of work, degree of sweating and climate.

Inhalation therapy - treating airway problems in the racehorse

Physiologically speaking, one of the major limiting factors to racehorse performance is how efficiently the lungs can exchange gasses. Training maximises the potential of any athlete, equine or human, to continue functioning at full throttle while the metabolism changes to deal with an oxygen debt in the muscle tissues. Clearly any threat to the efficiency of the lungs will result in poor performance. Horses are subject to a wide range of respiratory diseases; heaves, lung bleeding or exercise- induced pulmonary haemorrhage (EIPH), and exercise induced Airway Inflammatory Disease (IAD) among them. Another description of the same basic problem is Chronic Obstructive Pulmonary Disease or (COPD). Like all mammals, horses suffer from allergic reactions as well as viral and bacterial infections. The epithelial linings of the airways and the lungs are sensitive to infection or foreign bodies of any size, and the result is usually a mucosal discharge which blocks the airway.

Whichever route an animal has airway problems, by infection or allergy, the result is almost the same; mucous builds up, coughing and irritation, frequent nose bleeding and considerably reduced performance. Moreover, some animals with tendencies towards heaves can show little signs of respiratory stress at times, but can be triggered later, more frequently by pollen and dust, when a change in regime occurs. The treatment options can be quite different for horses with a zootic infection to those with an allergy. Treatment of IAD involves the use of bronchial dilators and steroids, which have treatment implications of their own. Some of the drugs used can cause the gut to become sluggish, and can lead to colic.

Many of them induce tachycardia, the speeding of the heart rate, and still others make the animal skittish and nervous. Similarly, the use of corticosteroids in cases of allergic response, can affect the immune system, lead to numbers of other opportunistic infections, particularly in the mouth and have been implicated in laminitis. Bronchodilators include substances well known to human medicine and their function is to cause the dilation of the airways, thus allowing more air in and out of the lung. When irritated, the airways constrict and then produce mucous, which is then countered by the drug. There are two types of drug used for dilation of the airways, and they work very differently in the horse.

The Salbutamol type inhalation works on receptors on the epithelial cells of the airway, relaxing the muscle, thus causing dilation. They work at best for around an hour. A second class of drug, anticholinergics, work on various parts of the larger airway. Consequently, a mixture of the two types of drug is frequently used. Nigel Haizelden of the Ledston Equine Clinic in Castleford, West Yorkshire has been using this therapy for over 12 years and states that all kinds of drugs are administered using this system. Using a nebuliser, antibiotics, corticosteroids and bronchodilators are regularly applied. He points out that “the nebuliser is used to get the specific particle size which is required to reach a certain part of the lung – this is critical to the treatment.” Another important aspect of the bronchodilator is that the easier breathing allows the animal to relax under exercise, something which tends to promote further airway dilation. However, they do nothing for inflammation. Treatment should be associated with a regime which removes the animal from possible irritants. Trainer magazine has dealt with varying aspects in recent issues, from dust-free bedding to pollen allergy; particularly that produced by Oil Seed Rape.

One of the problems of treatment has included the fact that in order to get the drugs into the animal, the whole horse has to be treated. Injecting a horse with drugs means providing a high enough concentration in the animal’s blood which, when diluted by the circulatory system and metabolised by the liver, there is enough at the site of operation to do its work. Consequently a much higher concentration of drug is used than would be required if it could somehow be administered solely where it is needed and nowhere else. Inhalation therapy has been used in humans for a long time, from the vapour baths of Victorian days to modern viral carrier gene manipulation therapy proposed for such disorders as cystic fibrosis.

There are a number of benefits. Firstly the lung is an excellent way of getting a balanced concentration of drug into the blood stream. It works very quickly. In the case of airway disease, the drug is being used directly at the point that it is needed, and consequently the amount of drug required to be effective is greatly reduced. This improves treatment options by reducing the possibility of side effects. There are a couple of products on the market that allow this type of therapy. The Aeromask and the Equine-haler. Both are available via the vet and come from the United States. Their use has become increasingly widespread across Europe, particularly in France and Germany, where there have been particular links with American racing practices. IN the UK they have been used for at least fifteen years and the treatment regimes have developed accordingly. The Aeromask is strapped onto the head and the drug is held in a reservoir called the spacer. The Equine-haler is a cone which has to be held over the nose of the animal while the drugs are placed in a compartment at the bottom. This allows for a metered dose aerosol to deliver a dose to the spacer which is then inhaled by the horse. It only works on one nostril, and a puff of medicine is released into the nose.

The Equine-haler need not be held in position all the time, it allows for a puff of medicine to be fired into a spacer which then can be applied to the horse when it breathes in next time. Between the two it should be possible to find a regime which will ideally suit any animal, those shy of the head bag of the Aeromask could easily treated by the Equine-haler and visa versa according to the treatment required. It is important that only a measured amount of drug is administered, under veterinary control, so that overdoses do not occur. Similarly, the equipment should not be used to administer anything other than prescribed medicines. One yard on the continent was reported to have used their own remedies in association with the mask, which consequently caused some blistering to the horse’s mouth.

There are some risks associated with the use of inhalation therapy. One is associated with the drugs themselves. These drugs are particularly effective on the metabolism of the animal. It produces dilation of blood vessels, particularly in the liver, and it also promotes the production of insulin. In America at least, where there are different rules in various states regards doping, trainers are advised to take advice before racing. However, this method of treatment has meant that withdrawal periods for horses under treatment are considerably reduced in comparison to former treatments. Another possible problem is associated with the effect of the drug on the mouth, where fungal infections have been associated in humans with constant use.

Back problems - how they can affect performance, and how to treat them

It is well documented that horses can suffer with back problems and they tell us by their actions. Sometimes the signs are blatant – for instance the horse stops jumping, or displays an obvious aversion to being saddled. Most of the time the signs are much more subtle. The animal may slightly change its way of moving in order to avoid pain and if untreated this becomes a chronic and long term problem, the slight change of gait becoming a progressive shortening of stride and a reduced level of performance.

The power source in the equine comes from the hind limbs propelling the body forward. If there is pain within that area the animal will use less power – and therefore go slower, or be unable to clear fences – than if it felt no pain. Traditionally we look at a horse being ‘trotted up’ in a straight line as a way of assessing soundness. This is an adequate measure in many cases where there is obvious lameness in one limb however a lame horse can ‘trot up’ sound and this shouldn’t be the only measure of soundness. Other tests such as trotting on a circle in both directions, on both hard and soft surfaces should be used. Assessing the animal at a walk on a level surface and observing from both the rear and from the side is also a very useful tool in diagnosing a slight lameness or restriction of gait. What manifests itself at a walk will still be there at a gallop. And knowing how the animal moves when sound and supple is key to knowing when something is starting to go wrong – perhaps catching a small problem before it becomes a serious lameness issue. Just saving itself from a fall or slip up when in the field can be enough to cause a problem.

A momentary error of judgment by horse or rider can force a horse to use its athletic ability to get out of trouble. A twist or over-big jumping effort can be enough. The horse can go on to complete the course or win the race that day but later, when the body has cooled down and the tired muscles are trying to recover pain can develop because of that over exertion. A subluxation may have occurred An almost imperceptible lameness or a restriction of free movement of the limbs can make all the difference between winning and losing. A slight ache or low grade back pain can make all the difference between staying the distance and tailing off last. Do horses have an ‘off day’? Or is there an underlying problem which is preventing full extension, making the animal hold itself back in order to avoid pain? The Spinal Cord is the keystone of the body. Maintaining its health and integrity is imperative in maintaining the health and wellbeing of the body as a whole, and doubly so in the case of a performance athlete.

The protection of the spinal cord is paramount in the actions of the horse or any vertebrate. The nervous system controls the whole body, with nerve control of practically every cell of the body. Subluxations or trapped nerves can interfere with the ability of the nervous system to function to the best of its ability both in control and in counteracting disease. Manipulation is therefore a means of reducing these subluxations to improve the functioning of the whole body. The skeleton is responsible for supporting the body and providing it with a strong framework consisting of rigid components which can move relative to each other at articulating joints. The spinal column provides protection to the spinal cord.

If a joint in the spinal column were to be dislocated that would result in damage to the spinal cord and paralysis or death. Between each pair of vertebrae a pair of spinal nerves leave the spinal cord through a small ‘gap’ in the muscles, ligaments and other soft tissues. A subluxation is where the joint between two bones is misaligned – muscles go into spasm and can pull one of the bones of the joint slightly out of alignment. If a joint is subluxated then the two surfaces are not quite in the correct position and nerves become impinged or ‘trapped’.

A nerve which has become trapped cannot send signals to muscles therefore function is affected. The equine athlete, and particularly the race horse, is highly susceptible to damage of the back, neck and poll. The body is put under a great deal of stress and pressure during breaking and fitness work whilst still immature. Added to this the horse must learn to carry the weight of a rider on its back and to balance itself with this shifting weight. Exertion such as galloping and jumping stresses the musculoskeletal structure and it is whilst under stress and when fatigued that injuries can occur more easily. The neck, chest withers and shoulders are of paramount importance to the action of the forelimbs.

The main nerves which feed the forelimbs leave the spinal cord between vertebrae in the lower neck and chest area (C6 –T2). If a horse struggles to flex and bend its neck to each side, up and down, shows stiffness or pain reactions it will cause restricted limb action, reduced ability to gallop, reduced speed, reduced stamina and reduced performance. As a highly strung and active animal the young horse is likely to be ‘sharp’ and difficult to handle during breaking. Whilst lunging they are prone to over-excitement resulting in leaping, bucking, rearing, spinning around etc - once backed they are still likely to display these behaviours. Rearing followed by unbalancing and going over backwards, or rearing whilst tied up with the entire weight of the body being taken over the poll region by the headcollar can lead to damage of the neck, withers and back. Rearing and hitting their head on a stable beam or flinging up the head and hitting it on the door frame or in a vehicle are all possible scenarios for damage to the poll and neck resulting in tension, pain and the development of other symptoms.

Sensitive withers can be just ticklishness but could also be soreness from the front limbs and neck. Concussion can travel right up the forelimbs resulting in sore withers. Of course a horse of any age can become sensitive in the neck and poll and often we do not know what they have done or when they have done it, unless it can be attributed to a particular incident such as a crashing fall or getting cast in the stable. Often the problem exists without explanation and could have been there for months or years – like living with a permanent head ache. Treatment with manipulation is straightforward and can give lasting relief. The main nerves which feed to the hind limbs leave the spine in the lumbar and sacral region (L4 - S2) and inflammation, soreness and pain in this area can and does cause the horse to take a shorter hind stride or unequal hind strides. The result of this will be a reduction in power leading to slower galloping speed and/or reduced stamina and failing to stay the distance.

The inexplicable poor performance of any horse could be attributed to any of the above. Fitness to do the job required is a vital part of injury prevention. Weeks of slowly building up the workload are necessary to attain the level of fitness needed for the job in mind. Additionally training involves keeping the body free from aches and pains which might lower the level of performance that the individual can attain. During training nerve damage can and does occur which will cause restrictive movement and a loss of straightness. This can be due to conformational defects, concussion, over-exertion, muscle strain, or injury.

There are no absolutes when it comes to conformation of the limb and the flight of the limb through the phases of a stride. Generally we look at conformation relating to the breed or type of the animal when standing. Some abnormalities or defects may only be evident during a phase of stride and may affect a pair of limbs or a single limb. Abnormal development within a joint can also cause a limb to exhibit a lateral gait defect. Normally the joints such as fetlock, carpus and tarsus work in a hinge-like fashion, backward and forward in a straight line parallel to the horse’s midline. An abnormality can produce a swivel-like motion and cause the limb to arc in flight. Even if a horse shows all the conformational traits that theoretically add up to straightness, if it experiences pain in any part of its body it may break all of the conformation rules in order to use its limbs in a manner which creates the least stress and pain.

An injury or soreness in a limb can cause a horse to protect one portion of the limb when landing, subsequently altering the arc of the foot’s flight. When a horse has pain in a part of the body other than the hooves or limbs, its balance during movement may be negatively altered as it compensates for the soreness. Back soreness can mimic lower limb lameness and alter foot flight. A variety of factors can cause a horse to carry its body in a stiff or crooked fashion. Sometimes the stiffness or pain is subtle but just enough to prevent the horse from tracking straight. As most people will know from personal experience – back pain reduces their ability to move freely, slows them down and if left untreated is debilitating and can lead to a long term loss of full musculoskeletal function together with general irritability.

This is no less the case in the horse and it does not necessarily mean that the horse is lame only that performance has been reduced. A horse suffering with back or neck pain will be unable to gallop as fast as it did prior to the injury, will be unable to ‘stay’ as far. The pain will restrict it and it will be unwilling to keep galloping thereby being seen to fade in the last furlongs or in severe cases never being able to lay up with the pace and being adrift from the offset. By being vigilant to the signs pain and of over-exertion and by allowing for recovery of the musculoskeletal system after work these problems can be minimised. The signs can be subtle but they are there – sometimes rest is needed, sometimes an injury has occurred which will require treatment.

Hoof Cracks - a very common problem in racehorses

A keen-eyed racegoer spotted a horse running in the USA last summer with six quarter cracks spread between three of its feet. While this number would be highly unusual in the UK, the problem of the hoof crack is not, and is one, which plagues the trainer, vet and farrier.

For the trainer, the words “The apple of your eye has popped a quarter crack, guv’nor,” are not welcome. Some great names have won Group One and other big races carrying hoof cracks, but the onset of a crack will result at minimum in serious problems in the horse’s preparation. Nevertheless, it is quite common for several horses to have cracks of one kind or another in a larger yard at the height of summer. “Some years you might have none, other years you might have two or three,” says Phil Brook, a leading Newmarket racing farrier who works with likes of David Loder, Chris Wall and Cheveley Park Stud.

The key to the treatment of hoof cracks lies in a determination of why they have occurred. This in turn relies on an understanding of the anatomy and dynamics of the hoof. TYPES OF HOOF CRACK Hoof cracks can occur at various locations on the hoof wall, and can be of varying degrees of severity. Cracks are normally defined by their location (toe, quarter or heel) and may also be defined by their type (e.g. sand, grass or horizontal) A grass crack originates at the ground surface and extends up the hoof wall; a sand crack originates at the coronary band, and runs downwards towards the base of the hoof. A horizontal crack runs more or less parallel with the coronary band. Cracks may be ‘superficial’ or ‘deep’. A deep crack can be defined as one, which has penetrated the sensitive laminae.

These are by far the more serious problem being the result of some trauma that has taken, or is taking place inside the hoof capsule. These can bleed during or after exercise and carry the additional risk of infection.

CAUSES OF CRACKS

Standard farriery textbooks will explain that the most likely cause of hoof cracks is either anterior-posterior (front to back) or medio-lateral (side to side) imbalance. Anterior-posterior imbalance may be caused by ‘long toe / low heel’ syndrome, which can result in breakover being forced too far forward through poor foot dressing. The pull of the deep digital flexor tendon conflicts with the point of breakover to cause a tearing of the laminae from the hoof wall and a consequent toe crack.

Likewise, medio-lateral imbalance may also be the result of the failure by the farrier to detect and correct, so far as is within his power, any imbalances. However, in most modern racing yards, good farriery can be taken as a given; and we have to look elsewhere for the causes of these cracks. Medio-lateral imbalance is more usually caused by conformation. Where it has not been possible to correct a limb imbalance when the animal was a foal, then the resultant incorrect loading will inevitably cause stress on other areas of the body, including the hoof. As the horse develops, this creates a potential for quarter-cracks.

A further cause may be injury – an overreach may cause injury to the coronary band, which results in poor hoof growth and a consequent crack in one area of the hoof. Alternatively, simply kicking the walls can open up a weak hoof or an old injury. “Thin-walled hooves with narrow heels can be particularly important causes of quarter-cracks,” says Phil Brook. “Likewise, flat and contracted feet can result in excessive tension at the coronary margin, also resulting in cracks.”

Another contributory factor is the breed itself. Bad feet are often inherited. If the hoof itself is of a weak structure, then it is even more susceptible to the development of cracks, whether through imbalances, conformation or injury. It is significant that cracks tend to appear in the spring and early summer as horses step up to faster work. All-weather surfaces have been cited as one of their root causes, the hard core exploiting any potential weaknesses in the hoof as both speed and concussion increase. Firm going may have the same effect.

TREATMENT OF CRACKS IN RACEHORSES

A hoof crack can never, of course, heal. The two sides of the hoof that have split will never grow together again. But, if the prime cause of the crack can be resolved, then there is usually no reason why good, solid hoof wall should not grow down from the coronary band to replace the area of the crack. The ultimate treatment for a serious hoof crack is of course rest. “Ideally,” says Phil Brook, “ you will want to get 1 – 1 ½ inches of growth from the coronary band before doing any work with the horse.” But for a horse in training, that is not often an option. Farriery techniques that might be used for the same problem on a horse that was not in training are not available to the racing farrier. For instance, lateral extension shoes to correct the weight-bearing through the hoof and limb, are not an optionwhilst the horse is in training, since these shoes will inevitably be lost in work and the problem perhaps exacerbated.

SUPERFICIAL CRACKS

Superficial cracks, which penetrate only the insensitive laminae, can normally be resolved by cleaning out and dressing by the farrier. It is important for the two sides of the crack to be separated so that the edges do not rub together as the hoof naturally expands and contracts with the horse’s action. If this is allowed to happen, then the crack will be perpetuated.

DEEP CRACKS

In the case of deep cracks, two different aspects of treatment are involved. On the one hand, action is required in order to address the original cause of the crack; and, on the other, the split hoof needs to be patched in order to immobilise the two sides, stabilise the hoof capsule and, when possible, allow the horse to continue to work. As Nick Curtis, farrier to Newmarket vets Greenwood Ellis, says, “You can put on any patch you want, but the underlying cause of the crack is what you need to find out. It is a 3-D thing – you have to take everything into consideration. The goal is to get the foot landing level and in line with the skeleton.” Without this double-handed attention, a horse can easily become lame. If, for instance, the two sides of a deep toe crack are pinching the sensitive laminae as the horse puts weight on the hoof, then lameness will follow. In addressing the cause of the hoof crack, the farrier has a number of options open to him. First and foremost, he will ensure that hoof balance is correct and will do whatever he can to correct any limb imbalances. Secondly he will probably use bar shoes to provide more support at the heel. On a racehorse, he is more likely to use ‘straight’ bar shoes than ‘egg’ bars, which can be pulled off in training and certainly in racing. Straight bar shoes are available either in steel or in aluminium versions. The aluminium version can be used for racing or simply as a lightweight therapeutic shoe. A secondary technique sometimes used is to relieve the bar shoe in the area directly beneath the crack in order to reduce the pressure being transmitted to that section of the hoof. This section of the hoof and shoe obviously has to be kept clean so that the effect of the relief is maintained. Thirdly, he may use a shock-absorbent sole packing material such as Vettec’s Equi-Pak. This is a liquid urethane dispensed onto the sole and frog which will ease concussion through the hoof. “Keep him off the all-weather surface for a while” could easily be additional advice from farrier to trainer. A nutritional supplement designed specifically for the hoof might also be recommended if the original problem has been a poor quality or thin-walled hoof.

PATCHING A CRACK

There are a number of ways that may be used to patch a crack, sometimes used on their own or in conjunction with each other. Shallow self-tapping screws may be inserted in the horn to either side of the crack. Wire or strong fibre filament is then wound between them to stabilise the crack. Similarly, a metal plate can be secured with screws on either side Wire can also be sutured directly into the good horn on either side of the crack without the use of screws. Another method, only open to the farrier over the last fifteen years, is the use of acrylic adhesives such as Equilox or Hoof Life and fibreglass cloth. Once the sensitive laminae exposed by the crack have healed sufficiently, a piece of fibreglass large enough to span the crack is impregnated with the adhesive, and is then applied over the surrounding area. Further adhesive is then applied on top To avoid infection, a straw or some form of removeable putty may be used underneath the adhesive, to create a cavity through which the area may be dressed and flushed out regularly. The acrylic or PMMA adhesives, whose main ingredient is Polymethyl Methacrylate, have proven the most effective in imitating hoof horn. Once cured, they can be rasped, and, when used for hoof repair, can be nailed into as if they were normal hoof wall. The Hoof Staple can also be used. This is a product resembling a double-ended fish-hook that spans the crack and is driven in on either side. In the USA, some senior veterinarians have started to use a product called Lacerum, manufactured by BeluMed X of Little Rock, Arkansas, in the treatment of hoof cracks. This is a platelet-rich plasma solution, obtained either from the horse being treated or a donor horse, that is used to promote healing, to accelerate the growth of healthy tissue and to fight off bacterial infection.

Thus, while cracks are, if anything, becoming more prevalent, new products and techniques are becoming available to the farrier as the result of developing technologies that permit him to address the issues in new ways and to find new solutions to the hoof crack problem. For further reading: ‘Farriery – Foal to Racehorse’ by Simon Curtis ‘No Foot, No Horse’ by Gail Williams and Martin Deacon ‘Hickman’s Farriery ‘(2nd Edition) by J. Hickman and Martin Humphrey ‘Principles of Horseshoeing II’ by D. Butler.

Do horses suffer from jet-lag?

The consequences of jet lag for the equine athlete have become more relevant in recent times due to increased travel of performance horses across multiple time zones for international competition. The effects of jet lag are significantly more detrimental for the professional athlete hoping to perform optimally in a new time zone. Before defining the implications of jet lag for the horse, it is first necessary to understand the effects of light on any mammalian system. Most all life on earth is influenced by the daily cycles of light and dark brought about by the presence of the sun and the continuous rotation of our planet around its own axis.

From the simplest algae to mammals, nearly all organisms have adapted their lifestyle in such a way that they organize their activities into 24-hour cycles determined by sunrise and sunset. For this reason, many aspects of physiology and behaviour are temporally organized into circadian rhythms driven by a biological clock. Thus, biological clocks have evolved that are sensitive to light and so enable physiological anticipation of periods of activity. Light is the primary cue serving to synchronize biological rhythms and allows organisms to optimise survival and adapt to their environment. An example of this environmental adaptation is clearly evident in the mare’s natural breeding season. As the number of hours of light gradually increases in the early spring, the mare’s reproductive system reawakens and within weeks is ready for conception.

With an 11 month, one week gestation period, horses have evolved to produce their young when the days are long and warm and the grass is green – the ideal environment for a growing animal and for a lactating mare with increased nutritional needs. However, we have interfered with nature’s design. With the creation of a universal birthday for Thoroughbred horses of January 1st and the economic demands to produce early foals for sale as mature yearlings, we have succeeded in altering the mare’s natural breeding season through use of artificial lighting programmes. A 200-watt light-bulb, in a 12-foot by 12-foot stall, switched on from dusk until roughly 11:00 pm nightly and beginning December 1st, is sufficient to advance the onset of the mares reproductive activity such that she should be ready to be bred by February 15th, the official start of the breeding season. From this, it is clear that light can control seasonal rhythms. What is more important in relation to jet lag is that light also closely regulates daily, or circadian rhythms. These circadian rhythms include changes in body temperature, hormone secretion, sleep/wake cycles, alertness and metabolism. A disruption of these rhythms results in jet lag.

It can be defined as a conflict between the new cycle of light and dark and the previously entrained programme of the internal clock. The first step to understanding jet lag is to examine the workings of the biological clock and the extent to which the daily cycles of light and dark can control physiological processes. All mammals possess a “master” circadian clock that resides in a specific area of the hypothalamic region of the brain. This area of the brain is responsible for regulating diverse physiological processes such as blood pressure, heart rate, wakefulness, hormone secretion, metabolism and body temperature. Each of these processes is in turn affected by time of day.

During daylight hours, the eye perceives light and light energy is transmitted via a network of nerve fibres to the brain. Here, the light signal activates a number of important genes and these “clock” genes are responsible for relaying signals conveying the time of day information to the rest of the body. Recent advances in the study of circadian rhythms and clock genes have shown that a molecular clock functions in almost all tissues and that the activities of possibly every cell in a given tissue are subject to the control of a clockwork mechanism. The role of the “master” clock in the brain is to communicate the light information to the clocks in the peripheral tissues, so that each tissue can use this information for its own purpose.

Thus, as day breaks and eyes perceive morning light, hormones are produced to help us to wake up, enzymes are activated in our digestive systems in anticipation of breakfast, heart rates increase, muscles prepare for exercise and many more circadian rhythms are initiated. This master clock in the brain, that controls so many bodily functions, must be reset on a daily basis by the photoperiod, whether it is sunrise and sunset or lights on and lights off, in order for an organism to be in harmony with its external environment. Jet lag occurs due to an abrupt change in the light-dark cycle and results from travel across multiple time zones, which in turn causes de-synchronization between an organism’s physiological processes and the environment.

Coupled to this is the fact that the circadian clock can only adapt to a new lighting schedule gradually and while the brain receives the light information directly, there is a further lag period involved in transmitting the time of day message to peripheral tissues. As a consequence, behavioural and physiological adaptation to changes in local time is delayed. This means that following a transmeridian journey, travellers are forced to rest at an incorrect phase of their circadian cycle, when they are physiologically entrained to be active and more importantly for the athlete, they are expected to perform when they are physiologically set to rest. As mammals, horses also suffer from the effects of jet lag.

Research is needed to understand the extent of physiological disruption caused by a transmeridian journey, the time period of the disruption and the overall effect it has on equine performance. Until now, no studies have been undertaken to investigate the physiological effects of jet lag in the horse. Studies in human athletes have demonstrated the detrimental effects of translocation on exercise capacity and performance. One early study examined human subjects following intercontinental flights consisting of eastward or westward journeys across multiple time zones (1). Results clearly demonstrated significant disturbances in heart rate, respiratory rate, body temperature, evaporative water loss and psychological function. Interestingly, these disturbances were found to be more profound following the eastward flight.

A more recent study conducted using top athletes from the German Olympic team investigated the effects of time-zone displacement on heart rate and blood pressure profiles (2). In athletes, blood pressure and oxygen supply to the organs are of utmost importance for optimal performance and successful competition. Rhythm disturbances in the 24-hour profiles of heart rate and blood pressure were found to be present up to day 11 after time-zone transition. The athletes were involved in intensive training programmes throughout the study and underwent frequent bouts of strenuous exercise.

Regular exercise at a set time in the 24-hour clock can strengthen circadian rhythms that are integral to physiological processes and can act as a timing cue secondary to light. It is also thought to aid in resynchronisation to a new time-zone. However, exercise was not found to improve the jet lag effects in this study, an observation that has relevance for the athletic horse in intensive training. The investigators concluded that following a flight across six time zones, athletes should arrive for their competition at least two weeks in advance in order to overcome the jet lag effects before competing.

Another study using fit human subjects examined performance times before and after an eastward journey across 6 time zones (3). Performance times for a 270m sprint were slower for the first 4 days following translocation as were times for a 2.8km run on the second and third days. This can be explained by the fact that the athletes’ internal body rhythms, including several neuromuscular, cardiovascular and metabolic variables and indices of aerobic capacity are out of synchrony with the environmental light-dark cycle following a transmeridian journey. Small mammals such as rats and mice have historically been used to study human circadian disorders such as jet lag. Current research being conducted at the Gluck Equine Research Center at the University of Kentucky has resulted in successful isolation of a number of ‘clock’ genes.

A comparison of these equine specific genes with their human counterparts has revealed an unusually high similarity between these two species at the DNA level, closer than the similarity observed between small mammals and humans. Unlike humans and horses, rats and mice are nocturnal animals and have yet to be proven as elite athletes. Further research is underway to investigate in detail the effects of jet lag on equine performance that will eventually lead to the development of measures to counteract these effects. Until then, information on the effects of transmeridian travel derived from studies on human performance can be used to provide guidelines to horse trainers, especially based on the similarity between the species in question. The severity of the jet lag effects can depend on a number of factors. These include the ability to preset the bodily rhythms prior to flying (4), the number of time zones crossed, the direction of the flight and individual variability.

Just as set exercise times can affect circadian rhythms in many physiological processes, feeding schedules also play an important role in entraining biological clocks, particularly within the digestive system. Horses anticipate feeding times. Banging of hooves on doors and rattling of empty feed buckets are common sounds that greet those responsible for feeding a yard of hungry horses. Therefore, it is important to change both feeding times and exercise schedules to mimic the new time zone prior to travel, in order to shorten the amount of time required for resynchronisation of digestive function and performance capacity upon arrival. Lighting is also of paramount importance. Exposing animals to early morning bright light for several days prior to an eastward journey across multiple time zones, or, extended hours of evening light prior to a westward journey, will help synchronize circadian rhythms to the new time zone prior to travel.

A recent study that tested a combination of approaches to hasten the resynchronisation of a group of elite sports competitors and their coaches to a westerly transmeridian flight, demonstrated the usefulness of combining melatonin treatment, an appropriate environmental light schedule and timely applied physical exercise to help the athletes overcome the consequences of jet lag (5). Melatonin, a hormone secreted by the pineal gland of the brain during the hours of darkness, is thought to help synchronize sleep-wake cycles and resynchronisation to a new time zone, but its suitability for these purposes has yet to be tested in the horse. Of course, these procedures to preset bodily rhythms need not be implemented if it is possible to arrive at the destination in sufficient time to allow natural re-entrainment to the new light-dark cycle.

For financial reasons, this is not necessarily feasible for the equine athlete. Two other important factors that determine the severity of jet lag effects are the number of time zones crossed and the direction of the flight. As one would expect, the greater the number of time zones traversed, the more severe the physiological disruption. For example, a flight from Europe to the East Coast of the United States, across six time-zones, would require a significantly greater resynchronisation time than a flight from the East Coast to the West Coast (three time zones), within the continental U.S. Any transmeridian journey in an eastward direction will result in a more profound disruption of circadian rhythms than a similar journey in a westward direction. The reason for this is a molecular one and involves the individual characteristics of certain clock genes. Suffice to say that clock genes react more rapidly to light than to darkness. When travelling in a westward direction i.e. from Europe to the United States, travellers enter an environment consisting of extended hours of evening light. The light continues to stimulate clock genes in the brain and adaptation to the new time zone occurs more rapidly. To some extent this may explain the success experienced by European horses at U.S. racetracks, even when they arrive three to four days prior to a race.

Knowing exactly how long it takes for the equine athlete to overcome any travel effects that may impinge on performance following such a flight, should provide valuable information to European trainers. In contrast, an eastward journey results in a shortened day length at the destination and requires a phase advance of the circadian clock. Travellers experience earlier nightfall and as the clock genes cannot respond well to darkness, an extended duration of jet lag. To emphasize, it will take an animal longer to adapt to the new light-dark cycle following an eastward flight and consequently longer to reach optimal performance levels following transit.

Pharmacokinetics deals with absorption, distribution, metabolism and elimination of drugs and these steps are influenced by physiological function of the body, which we now know to be influenced in turn by time of day. The implications of this for the athletic horse following transmeridian travel is worth highlighting, as it underlines the importance of knowing approximate physiological resynchronisation time to a new time zone. For example, terbutaline, a bronchodilator similar to clenbuterol commonly used by equine practitioners, has a significantly longer half-life when administered in the morning than in the evening (6). This implies that drug clearance times can be affected by transmeridian travel. In addition to the disruption of circadian rhythms, travel stress can also be a significant factor in further compounding the effects of jet lag following the transportation of horses across multiple time-zones.

Major complications associated with long-distance travel include pleuropneumonia, otherwise known as ‘shipping fever’, dehydration and colic. Even in cool conditions, horses will often lose 2-5 pounds of body weight for every hour they travel, as they do not like to drink while travelling (7). Care of horses during long-distance transportation is an extensive topic that requires separate attention. At the Gluck Equine Research Center, preparations are underway to conduct several experiments that will simulate phase advances and delays in the lighting schedule of groups of horses, thus mimicking eastward and westward journeys, so that the molecular and physiological effects of jet lag and the time duration of these effects can be investigated. The goal of this research is ultimately to provide practical guidelines to trainers in order that measures can be taken to counteract the detrimental effects of jet lag on performance, therefore leveling the playing field for horses competing away from home.