What if my mare did not get pregnant? Why embryo’s fail and improving odds of successful horse breeding

Words - Jackie Bellamy-Zions

If entering the winter, your breeding prospects have come up empty, there are considerations to ponder and actions you can take for successful breeding next year.  “Don’t let those mares sit all winter, with untreated conditions such as a uterine infection,” says Dr. Tracey Chenier, Theriogenologist and researcher from the Ontario Veterinary College at the University of Guelph.  “Have a thorough veterinary evaluation now to help ensure her uterus is clean and she is healthy and cycling early next year, for the best chance of a positive outcome.”

Common Issues Conceiving and Potential Solutions

“The number one reason your mare didn't get pregnant in any given year may be due to uterine infection,” says Chenier.  “The term we use is endometritis.”  Most often caused by a bacterial infection, it is often associated with poor perineal conformation.  In other words, your mare has a tilt to her vulva causing the vagina and uterus to become contaminated with bacteria every time she defecates.  It is also common for these mares to wind suck, which can lead to infection and inflammation that results in a hostile environment the embryo cannot survive in.  A minor surgical procedure known as a Caslick’s suture reduces the chance of contamination in most affected mares. Severely affected mares may require additional procedures to reconstruct the perineal body.

Another common form of endometritis is PBIE, or persistent breeding induced endometritis.   In these cases, there is a prolonged inflammatory response to semen and contamination that occurs at breeding.  Again, the mare has a hostile uterine environment in which the embryo cannot survive.  To improve the chance of conception, this condition can be managed by ultrasound within 6 to 12 hours after breeding.  She is checked for fluid retention and inflammation and if present, the uterus is lavaged to remove the fluid and calm the inflammation.  The veterinarian may also advise administration of oxytocin to increase uterine contractions and help remove the fluid.

Another very common reason for the mare not getting pregnant is their age.  “We actually consider mare’s fertility to decline as early as 12 years of age,” says Chenier, “and that surprises people that as early as 12 years, their fertility can decline significantly.”  Older mares can have poorer oocyte (egg) quality.  This reduces their chances of getting pregnant and can result in higher rates of mid-gestational losses.

Older mares are more susceptible to many circumstances including uterine conditions, metabolic disease, changes to the uterus, fibrosis and cysts.  Fibrosis of the uterus will reduce the chances of carrying a pregnancy to term.  Endometrial cysts or fluid filled sacs in the lymphatics of the uterus can block the ability of the embryo to move around and interfere with the placenta formation.

Less Common Conception Issues

“Stress, nutritional issues, and hormone deficiencies can make it difficult for an embryo to survive,” explains Chenier “but these issues are generally less common.”  

The corpus luteum is the structure that forms on the ovary after the mare ovulates and its progesterone production maintains the pregnancy early on.  This structure may be susceptible to effects of severe stress, illness, or inflammation in the uterus.  Progesterone/altrenogest supplementation can often save these early pregnancies but the mare will have to stay on the supplements until the fetoplacental unit takes over pregnancy maintenance by 120 days.  The fetoplacental unit is a crucial interface between maternal and foetal circulatory systems, providing essential nutrients and oxygen to support foetal growth and development.

Early pregnancy loss can happen from days 0–60 of gestation.  To help avoid risk factors like excessive stress, ask your vet before changing or adding anything to your mare’s routine. Consult your vet before administering any vaccines or deworming products.

“Oviductal blockage is another uncommon condition,” says Chenier, “but in mares that are not conceiving and everything else is normal (no uterine infection, good stallion fertility…) it should be considered.”  An effective treatment the veterinarian may suggest, involves applying the hormone prostaglandin E to the oviductal papillae, which opens the oviduct and allows that blockage to be cleared out. 

Diagnostics used to investigate early embryonic loss

“A good reproductive evaluation is really important to find out the reasons why a mare either didn't get pregnant or lost a pregnancy,” says Chenier.

Veterinarians use rectal palpation, especially with ultrasound, to help detect fluid and infection.  Palpation with ultrasound can detect the presence of endometrial cysts, conditions on the ovary, such as failure to ovulate and ovulatory follicles.

Cultures, gained from swabs of the uterus, are performed to detect inflammation and infection.  This is helpful in cases where antibiotic use is required in order to determine what type of antibiotic to use.

Uterine biopsy is indicated in certain cases.  “I recommend a biopsy in any mare that fails to get pregnant after three attempts, especially if we are not getting good answers on a swab culture and ultrasound,” says Chenier.  As well as providing a prognosis, it provides a lot of information on treatment options to improve the mare’s fertility.

A biopsy can help provide better information about what's going on in the uterus and in the case of inflammation, identify the type of inflammation present.

Chronic infections are more likely to be caused by something like a dormant strep infection, and biopsy may be the only way to diagnose the fibrosis of the uterus that would be directly related to prognosis.  If you found out your mare’s uterine biopsy was a Grade 3, meaning she has a lot of permanent severe changes in that uterus, her likelihood of carrying a foal to term is between zero and ten percent.  This is really important information to help the breeder to decide whether they want to invest the time and money to attempt to breed a mare with a prognosis revealing these challenges.

Ultrasound is useful in identifying conditions such as endometrial cysts.  Cysts can be removed by putting an endoscope in the uterus and then using either laser or electrocautery to a blade to improve a mare’s chances of pregnancy.  Electrocautery involves using a heated electrode to cut or coagulate tissue during surgery. When applied to a blade, it allows for precise cutting with minimal bleeding.

“In really rare cases where all else has been ruled out, a karyotype might be considered,” says Chenier.  “If it's a young maiden and everything else seems to be working, there may be a genetic reason that she's not able to get pregnant, but that would be the exception.”  Karyotyping involves staining chromosomes and examining them to identify structural changes or numerical abnormalities. 

Improving the odds of pregnancy

The all-important veterinary evaluation will check the mare’s general health, body condition and uterine health as well as rule out metabolic diseases like insulin resistance and Cushings.

One must ensure the broodmare’s nutritional needs are met.  Calories, protein, vitamins, and minerals are all passed on to the foal while in utero.  Consult your vet or an equine nutritionist to ensure your mare gets a balanced diet and to learn how her nutritional needs increase during pregnancy.

Use of light to manipulate the season is a consideration if you want to breed your mare early in the season for a January – March foal.  Mares stop cycling during the winter.  “I think it's helpful to expose the mare to the cold and the darkness of the fall to reset her system before you start her under lights,” say’s Chenier.  She recommends lighting programs begin around December 1st with what amounts to ten-foot candles, which is equivalent to 100 lux intensity of light.  In old style lighting with incandescent bulbs that was the 100 Watt bulb and the old saying was you needed to be able to read a newspaper in every corner of the stall.  16 hours of total light per day is recommended, and this includes natural light.  From a practical point of view, that means if you turn your mare out at 8:00 o'clock in the morning, bring her in at four, and have the lights on in the stall until 11:00 PM, you will be providing an adequate amount of light.  Chenier also describes the use of a commercially available equine light mask that is worn 24/7, like a fly mask.  It is battery powered and delivers blue light to one eye on a timed basis.

“Good breeding management is always key,” emphasises Chenier.  “Negative uterine swabs before breeding ensure the mare is free of infection, limit to one cover in mares prone to infection or inflammation, correcting poor perineal conformation and then practise optimal timing.”

Not breeding at the right time is much less likely in the thoroughbred industry, where mares are being bred by natural cover.  If the mare is not in heat and not ready to ovulate, she is not likely to stand for the stallion.  

If a mare is bred too early, the sperm will not live long enough.  Mares can stay in heat a day or two after they have ovulated.  If breeding happens too late (after ovulation), the oocytes will no longer be viable.

If the chosen stallion has fertility issues, the breeder may need to closely monitor their mare’s ovulation for the most optimal timing of breeding to improve odds of success.  Chenier says, “If their sperm doesn't live very long inside the mare, we have to manage those cases differently and make sure we're breeding those mares really close to ovulation to get good fertility for those stallions.”  Stallion fertility should always be considered a possibility when mares are not conceiving.

If breeding early in the season, one needs to make sure the mare is cycling properly and not just in spring transition.  A vet check will confirm the mare is experiencing a real heat and ovulating for early breeding (Feb – April).

Is SDFT tendinopathy a “professional condition” in the jumping racehorse?

Words - Jean Baptiste Pavard

Tendon and ligament disorders are one major cause of poor performance and wastage in equine athletes. The most common structures involved are the superficial digital flexor tendon (SDFT), the suspensory ligament (SL), the deep digital flexor tendon (DDFT) and the accessory ligament of the deep digital flexor tendon (ALDDFT), also called the inferior check ligament.

Thoroughbred racehorses are particularly predisposed to tendon and ligament injuries accounting for approximately 50% of all musculoskeletal injuries to competing racehorses. However, some structures are much more exposed to injuries than others in this population of equine athletes.

Most tendon injuries in racehorses occur to the forelimb tendons, with overstrain injury of the SDFT at the very top of the list. This is particularly true in jump racing, where the prevalence of superficial digital flexor tendinopathy has been found to involve up to 24% of horses in training over 2 seasons (Avella et al. 2009) and could be considered as a “professional condition”. 

The higher exposure of tendon injury in jumping horses compared to flat racehorses might be explained by the fact they compete over longer distances, for more seasons and are generally older than horses that race on the flat. Another reason is very likely that the SDFT of jumping horses support bigger strains, and repetitively, when landing over fences. 

The main issue for this type of injuries is that tendon healing is slow and requires a long recovery between 10 to 18 months depending on the severity of cases. Although the scar tissue of tendon injuries can be optimised with an effective rehabilitation program, its functionality remains inferior with relatively high re-injury rates in the years following the original lesion. Thus, a complete understanding of SDF tendinopathy and its major risk factors in jump racing are very important to improve prevention and early management of the condition which is a potentially career-ending condition. In the racing community, it has become crucial given big issues it involves in sporting and economic terms, as well as for the health and the welfare of racehorses. 

SDF tendonitis - characteristics in jumping racehorses

SDF tendinopathy is one of the most common injuries in jump horses with a prevalence from 10 to 45% depending on epidemiological studies with some variations among trainers. Most of the cases involve the forelimbs, but hindlimb injuries also occur. Typically, lesions are found at the mid-cannon level in a central core lesion. 

The disruption of the tendon fibres might generally occur in this area because it appears to be preferentially loaded and degenerates more over the time. However, injuries of the SDFT can be seen at all the levels of the tendon. They are most commonly unilateral, but bilateral SDFT injuries can also occur.

Tendinopathy is a result of mechanical overload, varying from single fibril disruption to complete rupture of the whole tendon. The most common cause of SDFT overstrain injuries in NH horses is an accumulation of damages from repetitive overloading. 

The structure of the tendons in horses is matured around 2 years old, and after maturity there is very limited or no adaptation possible. It means that if tendons accumulate an excess of micro-damage over the time (tendon cells have a capacity to repair defects, but it is limited and need time), they become weaker with a loss of elasticity and strength leading to a point where higher SDFT loads / strains result in disruption of fibres with a clinical tendon injury. 

Moreover, it is important to be precise that forelimb flexor tendons in racehorses function close to their maximal load / strain-bearing capacity with a narrow safety margin. While failure of the SDFT has been shown occurring for tensile strain* from 12 to 20% in vitro, peak strains within SDFT at the gallop are by around 16%. Since racehorses operate close to the functional limit of the SDFT during fast work, any risk factors that lead to higher loads on tendons during training or racing can result in clinical injury with significant disruption of tendon fibres. Some of these in NH horses are discussed below.

* % increase in length from original length / tensile strain

Causes – Risk factors

Epidemiological studies have identified risk factors for SDF tendinopathy in racehorses. As discussed previously, jump horses are at greater risk than flat racehorses and it could be partially explained by horses being older in jump racing. 

Indeed, risk of SDFT injuries increases considerably with age and it appears that the prevalence in jump horses is more important in horses older than 5 years old, with the maximum injury rate seen in horses 12 to 14 years of age. 

Other major risk factors identified for SDF tendinopathy are frequent high-speed work, longer race distance, harder racetrack surface, heavier bodyweight and longer training career. Although they were not clearly identified as such, fatigue in relation with exercise duration or lack of fitness and conformation / shoeing (long toe, low heel) might increase the risk of SDF tendon injuries.  

In jump racing, SDF tendonitis appeared more common in steeplechasers than in hurdlers, but the reason may be the older age of the first ones rather than the type of racing. 

Diagnostic

Assessment of suspected tendon injuries should be based on history and clinical signs associated with diagnostic imaging. In many racing stables, people assess forelimb flexor tendons daily which can help to detect the early lesions of SDF tendinopathy. 

However, first signs may be very subtle and variable depending on history, severity and location of injury. They are usually noted within 24 hours of fast work or racing but can also develop at slower work. It is often subclinical and resolves quickly for non-severe injuries with acute lesions characterised by heat, soft tissue swelling and pain on palpation, whilst chronic ones appear with fibrosed thickening. 

Overstrain SDFT injuries are classically in the mid-cannon area and present a more or less severe change in profile of the back of the limb leading to the well-known qualification of “bowed tendon”.  

However, the obvious signs of inflammation (thickening and heat) are not always present even for some significant injuries and lameness doesn’t appear to be a very consistent feature associated with SDFT injuries. It is typically mild (1 to 2 grades out of 5 at the trot) and improves rapidly over the first week after the injury, however the tendon remains weakened. Consequently, the level of lameness and pain on palpation don’t have a good correlation with the severity of the lesion, except in the most severe cases.

In cases of apparent “bowed” injury with pain response on palpation, it is sufficient to consider there is likely an active tendonitis. In more subtle configuration, the need for ultrasound is indicated to confirm and assess the extent of the lesion.  

It may be best to perform or repeat tendon scans at 1 to 3 weeks after clinical injury first noted. Indeed, it allows us to assess lesion severity more accurately because of ultrasonographic underestimation of lesion extent at the beginning of tendon injuries. It is also very important in cases of suspected lesions but initially not well defined. 

Moreover, both tendons should be systematically examined on ultrasound for 2 major reasons. Firstly, SDFT tendinopathy are bilateral in up to 67% of cases (Webbon), and secondly it helps to differentiate active lesions versus subclinical changes on ultrasound (ex. “juvenile tendinitis”). A careful ultrasound assessment is also keen to exclude the presence of potential concomitant lesions (ex. SL desmitis).

When SDFT lesions are suspected, the horse should be put at stall rest with only short hand walking until the injury is confirmed or not by ultrasound a few weeks later.  

Ultrasound is routinely used by equine veterinarians and is elected to diagnose SDFT injuries as first-line diagnostic imaging. Whilst it is particularly relevant to document tendon lesions, it has been beneficial to develop a scoring system using specific measurements in order to categorise the severity of SDFT tendinopathy. 

It is also very useful to establish prognosis and monitor the healing process in line with an adapted rehabilitation program.

Prognosis and return for racing

The prognosis of SDF tendinopathy can be very variable depending on the severity of injury, the convalescence program and the type of racing. Overall, sport prognosis in the Thoroughbred is guarded with a reported return to racing from 20 to 60 % of cases. The major issue of tendon injuries in racehorses is the need for a long recovery and the high rate of re-injury due to poor regenerative capacity of tendon tissue, which is considered as a limiting factor for racing. However, return to training / racing activity is common for most mild / moderate SDFT injuries.

A study with jump racehorses affected by SDFT injuries classifying lesions severity by ultrasound established that all horses with mild lesions returned to training, and 63% raced. 50% of moderately affected horses returned to training, and 23% raced. 

In severe lesions, only 30% of horses resumed training, and 23% raced. In the study, the mean of reinjury rate for horses resuming work was 40% over a period of follow-up from 9 to 30 months, but some studies with longer follow-up reported up to 80% of horses sustaining a re-injury. Also, it is remarkable to note that a significant number of re-injuries affect the opposite normal limb.

Definitely, long-term prognosis is influenced by the severity of the lesions. The more severe SDFT lesions are, the lower chance of return to racing, shorter racing career and drop in racing class of those resuming there are. Complete ruptures of SDFT are hopeless for sport prognosis, but paddock life remains possible. 
The other factors established to influence the sport prognosis in racehorses affected by SDFT lesions are concomitant lesions, and more particularly bilateral tendinitis which have very poor prognosis. The less classical SDFT lesions like those at the level of carpal or proximal cannon have poorer prognosis for racing and ongoing lameness is frequently present. While it is difficult to study the influence of rehabilitation programs due to the need for a long period of follow-up, controlled exercise showed to provide better prognosis than only uncontrolled pasture rest. 

Treatment & Management: How to optimise the healing of tendon lesions?

Contrary to bone, healing of tendon lesions doesn’t allow you to get back pre-injury tissue due to its poor regenerative capacity. It means the structure and function of healed tendons are modified with different mechanical properties. Thus, the aim of SDF tendinopathies’ treatment is to optimise the healing process in order to get a strong and functional repaired tendon as much as possible. 

Although there are different options available in the management of SDFT lesions in racehorses, all of them should respect a long recovery with progressive return to work. As said previously, tendon healing is slow, and it is common to consider at least 12 months for return to racing in horses affected by SDFT injuries. 

To understand how to manage SDFT tendinopathy, it is important to consider the different phases in the tendon healing process.

In the initial days following the injury, the acute phase is characterised by inflammatory reaction. For a long time, it was advised to control quickly and aggressively the inflammatory response to limit damage to the tendon. However, it is now more and more controversial because the initial inflammatory phase would be beneficial for the repair process of tendons. 

The best management of this phase is to treat only in case of excessive pain and acute swelling through the use of anti-inflammatory drugs and cold therapy locally for a period of 3 to 5 days. During this phase, it is important to minimise exercise with stable confinement for the initial weeks. As we discussed previously, the ultrasound assessment of tendon injuries is generally best performed 1 to 3 weeks after the initiation of the injury because it allows to determine the full extent of the lesion. Thus, it is recommended to scan flexor tendons at the end of the acute phase to grade the severity of the lesion and establish a rehabilitation program and prognosis for return to racing activity. 

The other crucial period in the management of SDFT tendinopathy is the rehabilitation phase which can begin soon after the inflammation subsides. The cornerstones of healing tendon are the need for time and progressive graded and controlled exercise program. Protocols are quite empirical due to the difficulty to compare long-term outcome with homogenous groups. 

Indeed, the program should be determined in relation to the severity of the injury, but classically at least 6 months are necessary for return to cantering. A typical program is to introduce walking once the acute phase has passed with gradual increasing duration until 12 weeks. Ideally, monitoring of healing with ultrasound assessment every 3 months allows to control the evolution of the repair through an assessment of fiber pattern alignment and tendon/lesion size. In normal evolution, trotting can be introduced after 12 weeks and cantering after 32 weeks. Generally, the re-introduction to normal race training is resumed not before 8 to 12 months. Prognosis of SDFT lesions reported for horses rested for less than 6 months is poorer with higher risk of re-injury. 

Additional therapies can be used in the aim of optimising the healing of tendon tissue after injuries. Some of them are more and more popular and promising, but it is still difficult to evaluate and compare their efficacy. These modalities have to be considered as an additional intervention to graded exercise programs. 

The main interest of these therapies is not to reduce rehabilitation, but to optimise the healing process reducing the chance of re-injury after return to training. These additional therapies range from firing to intralesional therapies with PRP (Platele-rich plasma), PSGAGs (Polysulfated glycoaminoglycans), growth factors (IGF-1) or stem cells. To optimise the efficiency of these therapies, the treatment should be generally realised during the acute phase (more or less 2 weeks after the initiation of the injury). 

How SDF tendinopathy can be prevented in racehorses

Prevention is very important due to long recovery and guarded prognosis linked to high re-injury rate. 23–67% of horses with tendon injury treated using conservative methods will re-injure their tendons within 2 years of the original injury.

Strategies with success in preventing/reducing the incidence of tendon injury have not been validated; however, awareness of risk factors associated with SDFT tendinitis provides some useful guidance. 

• Avoid excessive training to fatigue and permit sufficient recovery time after racing or high-speed training. 

• Avoid use of poorly prepared or inappropriate track surfaces. 

• Long-term use of exercise boots/bandages may also contribute to increased risk; magnitude of this risk is unknown but should be balanced against rationale for routine use of bandages in horses that are not prone to interference injuries. 

• Strategies to reduce risk of reinjury of a rehabilitating/ rehabilitated tendon have also not been validated; however, it is rational to limit excessive loading of tendon. 

• Possible aspects to assist with above: incorporate treadmill use in training programme; attention to rider weight; minimise horse accruing excessive body condition; ensure maintenance of good dorsopalmar foot balance. 

• Possible benefit to be derived from regular post-exercise cryotherapy (such as cold water immersion): cooling the lower limb effectively can reduce enzymatic activity in tendon and potentially inhibit cell attrition resulting from high-intensity exercise. 

Tracks that are very hard result in higher speeds and increased peak impact loads. These fast tracks are therefore more likely to produce overstrain injuries of tendons. 

However, tracks where the surface is uneven, slippery, or shifty seem also to contribute to damaging loading patterns on tendons. Numerous factors influence the mechanical behaviour of a track surface; the weather and track maintenance have a major influence. Moisture content affects all tracks’ mechanical properties, and extreme temperatures appear to affect some synthetic tracks’ mechanical characteristics dramatically. 

Experience over years with a particular track type will allow identification of track conditions that may predispose to tendon injuries.

Fatigue is influenced primarily by the horse’s work schedule, level of fitness, and intensity of competition. Fatigue should be considered as a contributor to tendon injuries. With the onset of muscle fatigue, a horse’s stride characteristics change,13 altering the forces on the tendons. Fatigue in any sport results in an inevitable loss of form and coordination in each stride, which is likely to result in an increased risk of injury.

At high speed, lameness may result in excessive loading of the tendons in the contralateral limb.

Horses who are overweight or carrying excess weight will produce greater forces on their tendons compared with lower weight individuals.

Conclusion

In conclusion, tendon and ligament disorders prove to be a major cause of poor performance and lameness within the racing industry. With SDF tendinopathy being at the forefront of these lameness’, there are many strategies that can be adopted to prevent / reduce the incidences of tendon injuries within the thoroughbred.

Stem Cell Therapy - the improved diagnostics available to treat lameness

Article by Jackie Zions (interviewing Dr. Koenig)

Prevention is the ideal when it comes to lameness, but practically everyone who has owned horses has dealt with a lay-up due to an unforeseen injury at some point. The following article will provide tools to sharpen your eye for detecting lameness, review prevention tips and discuss the importance of early intervention. It will also begin with a glimpse into current research endeavouring to heal tendon injuries faster, which has obvious horse welfare benefits and supports horse owners eager to return to their training programs. Dr. Judith Koenig of Ontario Veterinary College (OVC) spends half of her time as a surgeon and teacher with a strong interest in equine sports medicine and rehabilitation, and the other half as a researcher at the OVC.

Lameness is a huge focus for Koenig, whose main interest is in tissue healing. “I think over the past 20 or 30 years we have become very, very good at diagnosing the cause of lameness,” says Koenig. “In the past, we had only radiographs and ultrasound as a diagnostic tool, but by now most referral centres also have MRI available; and that allows us to diagnose joint disease or tendon disease even more. We are much better now [at] finding causes that previously may have been missed with ultrasound.” 
Improvements in diagnostics have resulted in increased ability to target treatment plans. With all the different biologics on the market today, Koenig sees a shift in the management of joint disease with more people getting away from steroids as a treatment.

The following list is excerpted from Equine Guelph’s short course on lameness offered on TheHorsePortal.ca. It outlines the different diagnostics available:

When asked for the latest news on research she has been involved in, Koenig proclaims, “I'm most excited about the fact that horses are responding well to stem cell treatment—better than I have seen any response to any other drug we have tried so far!”

Koenig has investigated the use of many different modalities to see if they accelerate tissue healing and has studied which cellular pathways are affected. Two recent collaborative studies have produced very exciting findings, revealing future promise for treating equine osteoarthritis with stem cell therapy.  

In a safety study, Koenig and her team at the Ontario Veterinary College have shown equine pooled cryopreserved umbilical cord blood, (eCB) MSC, to be safe and effective in treatment of osteoarthritis.  

“These cells are the ones harvested from umbilical cord blood at the time of foaling and then that blood is taken to the lab and the stem cells are isolated out of it,” explains Koenig. The stem cells are then put through a variety of tests to make sure they are free of infectious diseases. Once given a clean bill of health, they are expanded and frozen. 
The stem cells harvested from multiple donors of equine umbilical cord blood [eCB, (kindly provided by eQcell), MSC] were compared to saline injections in research horses. “This type of cells is much more practical if you have a cell bank,” says Koenig. “You can treat more horses with it, and it’s off the shelf.” There were no systemic reactions in the safety study. Research has also shown no different reactions from sourcing from one donor or multiple donors.  

In the second study, 10 million stem cells per vial were frozen for use in healing OA from fetlock chips in horses that were previously conditioned to be fit. After the fetlock chip was created, exercise commenced for six more weeks, and then osteoarthritis was evaluated by MRI for a baseline. Half the horses were treated with the pooled MSC stem cells, and the control group received saline before another month of exercise. Then MRI and lameness exams were repeated, and arthroscopy was repeated to score the cartilage and remove the chip.

Lameness was decreased and cartilage scores were improved in the group that received stem cell therapy at the time of the second look with arthroscopy.

Many diagnostics were utilised during this study. MRIs, X-rays, ultrasounds and weekly lameness evaluations all revealed signs of osteoarthritis in fetlock joints improved in the group treated with (eCB) MSCs. After six weeks of treatment, the arthroscopic score was significantly lower (better cartilage) in the MSC group compared to the control group. 

“Using the MRI, we can also see a difference that the horses treated with stem cells had less progression of osteoarthritis, which I think is awesome,” says Koenig. “They were less lame when exercised after the stem cell therapy than the horses that received saline.”

This research group also just completed a clinical trial in client-owned horses diagnosed with fetlock injuries with mild to moderate osteoarthritis changes. The horses were given either 10 million or 20 million stem cells and rechecked three weeks and six weeks after the treatment. Upon re-evaluation, the grade of lameness improved in all the horses by at least one. Only two horses presented a mild transient reaction, which dissipated after 48 hours without any need for antibiotics. The horse’s joints looked normal, with any filling in the joint reduced.
There was no difference in the 18 horses, with nine given 10 million stem cells and the other nine 20 million stem cells; so in the next clinical trial, 10 million stem cells will be used.

The research team is very happy with the results of this first-of-its-kind trial, proving that umbilical cord blood stem cells stopped the progression of osteoarthritis and that the cartilage looked better in the horses that received treatment. The future of stem cell therapy is quite promising!
Rehabilitation
Research has shown adhering to a veterinary-prescribed rehabilitation protocol results in a far better outcome than paddock turn out alone. It is beneficial for tendon healing to have a certain amount of controlled stimulation. “These horses have a much better outcome than the horses that are treated with just being turned out in a paddock for half a year,” emphasises Koenig. “They do much better if they follow an exercise program. Of course, it is important not to overdo it.”

For example, Koenig cautions against skipping hand-walking if it has been advised.  It can be so integral to stimulating healing, as proven in recent clinical trials. “The people that followed the rehab instructions together with the stem cell treatment in our last study—those horses all returned to racing,” said Koenig.  

“It is super important to follow the rehab instructions when it comes to how long to rest and not to start back too early.”

Another concern when rehabilitating an injured horse would be administering any home remedies that you haven't discussed with your veterinarian. Examples included blistering an area that is actively healing or applying  shockwave to mask pain and then commence exercise.

Prevention and Training Tips
While stating there are many methods and opinions when it comes to training horses, Koenig offered a few common subjects backed by research. The first being the importance of daily turnout for young developing horses.  

Turnout and exercise
Many studies have looked at the quality of cartilage in young horses with ample access to turn out versus those without. It has been determined that young horses that lack exercise and are kept in a stall have very poor quality cartilage.
Horses that are started early with light exercise (like trotting short distances and a bit of hill work) and that have access to daily paddock turnout, had much better quality of cartilage. Koenig cited research from Dr. Pieter Brama and similar research groups.

Another study shows that muscle and tendon development depend greatly on low grade exercise in young horses.  Evaluations at 18 months of age found that the group that had paddock turnout and a little bit of exercise such as running up and down hills had better quality cartilage, tendon and muscle.  

Koenig provides a human comparison, with the example of people that recover quicker from injury when they have been active as teenagers and undergone some beneficial conditioning. The inference can be made that horses developing cardiovascular fitness at a young age stand to benefit their whole lives from the early muscle development.

Koenig says it takes six weeks to regain muscle strength after injury, but anywhere from four to six months for bone to develop strength. It needs to be repeatedly loaded, but one should not do anything too crazy! Gradual introduction of exercise is the rule of thumb.

Rest and Recovery
“Ideally they have two rest days a week, but one rest day a week as a minimum,” says Koenig. “I cannot stress enough the importance of periods of rest after strenuous work, and if you notice any type of filling in the joints after workout, you should definitely rest the horse for a couple of days and apply ice to any structures that are filled or tendons or muscles that are hard.” 

Not purporting to be a trainer, Koenig does state that two speed workouts a week would be a maximum to allow for proper recovery. You will also want to make sure they have enough access to salt/electrolytes and water after training.

During a post-Covid interview, Koenig imparted important advice for bringing horses back into work methodically when they have experienced significant time off.
“You need to allow at least a six-week training period for the athletes to be slowly brought back and build up muscle mass and cardiovascular fitness,” says Koenig.  “Both stamina and muscle mass need to be retrained.”

Watch video: “Lameness research - What precautions do you take to start training after time off?” https://www.youtube.com/watch?v=zNHba_nXi2k

The importance was stressed to check the horse’s legs for heat and swelling before and after every ride and to always pick out the feet. A good period of walking is required in the warmup and cool down; and riders need to pay attention to soundness in the walk before commencing their work out.

Footing and Cross Training
With a European background, Koenig is no stranger to the varying track surfaces used in their training programs. Statistics suggest fewer injuries with horses that are running on turf. 

Working on hard track surfaces has been known to increase the chance of injury, but delving into footing is beyond the scope of this article.

“Cross training is very important,” says Koenig. “It is critical for the mental and proper musculoskeletal development of the athlete to have for every three training days a day off, or even better provide cross-training like trail riding on these days." 

Cross-training can mitigate overtraining, giving the body and mind a mental break from intense training. It can increase motivation and also musculoskeletal strength. Varied loading from training on different terrain at different gaits means bone and muscle will be loaded differently, therefore reducing repetitive strain that can cause lameness.

Hoof care
Whether it is a horse coming back from injury, or a young horse beginning training, a proficient farrier is indispensable to ensure proper balance when trimming the feet. In fact, balancing the hoof right from the start is paramount because if they have some conformational abnormalities, like abnormal angles, they tend to load one side of their joint or bone more than the other. This predisposes them to potentially losing bone elasticity on the side they load more because the bone will lay down more calcium on that side, trying to make it stronger; but it actually makes the bone plate under the cartilage brittle.  

Koenig could not overstate the importance of excellent hoof care when it comes to joint health and advises strongly to invest in a good blacksmith. Many conformational issues can be averted by having a skilled farrier right from the time they are foals. Of course, it would be remiss not to mention that prevention truly begins with nutrition. “It starts with how the broodmare is fed to prevent development of orthopaedic disease,” says Koenig. Consulting with an equine nutritionist certainly plays a role in healthy bone development and keeping horses sound.