Sports Medicine Meeting
The 17th annual meeting of the Association for Equine Sports Medicine was held in Leesburg, Va., from March 5-8. The meeting was attended by 400 veterinarians, sports physiology researchers, as well as others interested in equine health. The meeting offered topics ranging from how stall housing can impair bone development in young horses, to diagnostic thermography. The following highlights some of the presentations at this year's AESM meeting.
Care Of Tendons And Ligaments
Research showed that supplementing HMB in training and racing Thoroughbreds increased performance.
Signs of ligament or tendon injury will vary, but, according to Reef, "The most frequent indication of tendon or ligament injury is swelling in the affected limb in the tendon or ligament area. Heat and sensitivity on palpation of the injured area are also frequently detected. Lameness is present in less than 50% of the horses with tendon or ligament injury. An injured tendon or ligament should be suspected when the characteristic signs of swelling, heat, and sensitivity in the flexor tendon or ligament are detected, even if the signs are only transient."
Reef went on to say that ultrasonography has become a key instrument in detecting tendon and ligament injury, the extent of the injury, as well as assessing the healing process. Ultrasonography has been incorporated into the rehabilitation program for horses which have suffered these types of injuries, said Reef.
Peggy Miller, Iowa State University, and John C. Fuller Jr., Metabolic Technologies Inc., conducted a study on the effects of supplemental B-hydroxy-B-methylbutyrate (HMB) involving 48 racing Thoroughbreds to determine if HMB was beneficial in training racing Thoroughbreds. Supplemental HMB use in humans has been shown to decrease muscle protein breakdown while shortening the recovery time for muscles associated with intense exercise and possibly increasing endurance of the athlete due to an increase in aerobic capacity.
After three weeks of being fed the HMB supplement, the horses showed a 5% increase in red blood cells. After the first race, HMB supplemented horses had 46% lower creatinine kinase levels with a 15% decrease in other muscle-related enzymes and an increase in white blood cell counts by the end of the meet. According to the paper presented, "Improvement in horse condition resulted in an 18.8% win rate for HMB-supplemented horses compared with 11.4% win rate for the controls (which didn't receive HMB). In conclusion, supplementing HMB in training and racing Thoroughbreds was shown to increase overall performance because it decreased training and race-related muscle damage and increased aerobic capacity."
Housing And Bone Formation
Researchers in the Department of Animal Science, Michigan State University, conducted a study on the effects stall housing has on young horses in relation to skeletal injuries sustained once they were placed in a training program. The study consisted of 16 Arabians at 18.6 months of age, which were divided into two groups -- one group was kept in stalls and the other group was turned out to pasture.
"After an 84-day pre-training period, six horses from each group were randomly chosen to complete a 56-day training period. Every 28 days, radiographs of each horse's left front leg were taken to measure mineral content of the third metacarpal, as determined by radiographic bone aluminum equivalencies (RBAE), and 24-hour urine collections were taken to measure urinary deoxypyridinoline. Every 14 days, blood samples were taken 11 hours post-feeding to measure serum osteocalcin concentrations."
It was found that RBAEs of the lateral cortex decreased in the horses which were confined to stalls. The horses in stalls also had a lower rate of osteoblastic activity in their bones compared to the pasture group at Day 14. After Day 14, osteoblastic activity in the stall horses returned to baseline.
The study concluded, "It appears that transferring young, growing horses from pasture to stalls negatively affects normal bone growth due to limited access to forced or free exercise. Initial training did not alleviate the negative effects of the change in housing on bone formation."
Horses have 168 joints in their spines and 42 joints in their lower limbs. With this number of joints, the possibility of something going wrong is a definite concern. Researchers at the University of Pennsylvania conducted a study to examine the care of the back in performance horses.
According to Benson Martin, Jr., VMD, Dipl. ACVS, "Addressing many of the problems, include feeding a diet appropriate for the level of exercise, being reasonable in making demands on the horse's exercise regime, insuring at least 15-30 minutes of warm-up before any serious exercise, insuring a long period of cooling out afterwards, insuring the tack is in good order and is a proper fit for the particular horse, insuring the horse is well-shod, insuring soundness problems are addressed in a timely fashion, and if necessary, consulting with your veterinarian if your horse has any untoward changes in performance, habits, or attitude."
After making use of radiology, ultrasound, thermography, scintigraphy, treadmill, lameness exam, etc., your veterinarian will be able to diagnose the problem at hand and assist in correcting it. A proper exercise plan, along with therapy, should be undertaken in order to bring your horse back to his prior performance level.
Bone And Joint Development
Questions about young Quarter Horses have been raised concerning longing them at early ages and the effect that has on their developing long bones. Researchers at Michigan State University have conducted research to address these concerns. Twenty-one yearling Quarter Horses were used in this study to "examine the effects of longing and glucosamine supplementation on known biological markers of joint and bone metabolism in yearling Quarter Horses," according to the study.
The study concluded that horses receiving glucosamine supplements tended to have higher keratin sulfate (marker for cartilage degradation) compared to non-supplemented groups. Longed horses tended to have lower osteocalcin (marker for bone formation), while horses given supplements and which were walked tended to have more bone formation when compared to the horses which were longed with or without supplementation.
Feeding the 3-Day Event Horse
According to Pat Harris, PhD, VetMB, MRCVS, good nutrition in the three-day event horse will bring out his optimal performance. Make sure adequate, and appropriate, levels of energy are fed to the horse as a crucial part of the diet. Be sure not to feed too much, or you run the risk of getting an overweight horse which ends up lethargic, has digestive disturbances, or could colic. However, according to Harris, you want to feed enough energy to supply the horse with the appropriate weight and condition scoring that is required.
What is the right amount of energy to feed? When answering this question, Harris said horses are individuals, just like people, and individual needs must be kept in mind when feeding -- some horses are easier keepers than others.
Cereals are fed to horses as an energy supply. Energy itself is not a nutrient, but cereals are converted by the horse into ATP, which releases energy. Harris also pointed out that horses do not have the capability to break down large amounts of starches. To help with this, feed smaller meals more frequently. The larger the amount you feed the horse, the faster the horse's gastrointestinal tract rids the feed from its body before full nutrition is gained from the meal. The horse has evolved as a grazer, which means his GI system is designed to have frequent and small meals. Harris says, "The horse will get more nutrition from more frequent, small meals than he will from the same amount fed at one time."
Feeding fat to horses also was addressed by Harris. He said, "You must train on a fat-supplemented diet because it takes weeks to months for a horse's body to adjust to the fat content." Harris advised not to feed fat right before you begin to show because your horse's body will not be adjusted to the added fat and it will reflect in his performance.
Harris also warns that feeding too much fat will result in an overweight horse, oily feces, an easily excitable horse, or an upset gastrointestinal tract. Harris' final word on fat was that no more than 10% of the total diet should be fat.
As a final word on diet, Harris says, "Feeding for performance is a balancing act." Harris added that part of the reason you warm horses up before riding is to activate mechanisms in the horse that release energy.
According to Nathaniel White II, DVM, Dip. ACVS, if radiographs are taken and you don't see spaces between bones (cartilage), then the cartilage is damaged, or absent. Signs of joint disease include joint fluid that has increased protein levels and abnormal cells. An ultrasound will expose thickened joint capsules or bone chip fractures. Scintigraphy will aid in showing which areas of the affected area are "hot," which will indicate where the problems are located.
Ideally, joint fluid should be clear. If it appears cloudy, then it's an infected joint.
Non-steroidal anti-inflammatory drugs (NSAIDs) are used to treat inflammation in joint problems. However, White points out that continued overuse of NSAIDs over an extended period of time can produce gastric ulcers in the GI tract of the horse, in which case the drugs become toxic to the animal.
Other treatments of joint disease include hyaluronic acid (HA) to promote the production of good fluid in an infected joint. In the past, fluid from a good joint was transferred into the affected joint, but today, HA allows this procedure to be performed with synthetic joint fluid.
Corticosteroids also are commonly used to treat joint disease. By reducing water movement in and out of the joint, corticosteroids preserve the joint during the healing process. Polysulfated GAGs, which are given intra-articularly, preserve cartilage and keep it from further breaking down. Polysulfated GAGs are very beneficial in repairing cartilage. Oral GAGs such as Cosequin and Flex-Free aid in protecting joints from disease.
Other treatments of joint disease include arthroscopic exploration, which is used as a diagnostic tool as well as a treatment for horses with joint problems. Joint flushes are used to get rid of damaged cartilage, which allows new cartilage to grow in its place. Immobilization and rest also are beneficial when treating this type of injury.
White concluded his talk by pointing out that the primary infection-causing joint problems might be in the bone, in which case the problem with the bone needs to be addressed in order to care for the joint.
Reaching Potential With Hooves
Many horses never reach their full potential because of their feet, according to Scott Pleasant, DVM, MS, Dip. ACVS. Pleasant said that good feet consist of good conformation and hoof care.
The growth of the hoof is from the coronet down, and usually at a rate from zero to one-half inch per month -- slower in the winter and faster in the summer. Pleasant noted that some horses will grow hooves faster than others. The horses which grow hooves slowly will be a problem for the farrier because those horses will be a challenge to keep shoes on.
We've all heard the saying about white vs. black feet, but according to Pleasant, there is really no difference in strength or growth rate between these two colored hooves.
The foot is designed to absorb and dissipate pressures upon it. With this in mind, the larger the hoof, the better it's able to perform this task.
A healthy hoof should have the following attributes: The hoof wall thickness needs to be secure in order to absorb the pounding shock of hitting the ground and also to hold the shoe in place. The sole should be concave. The hoof should be wider as it goes toward the ground -- if this doesn't happen, then the hoof does not absorb shock well and the blood flow in the hoof suffers. Hoof angles are specific for each horse, with the slope of the hoof matching the slope of the pastern. Pleasant also said the slope of the heel should be the same as the slope of the toe.
A question many owners ask is whether or not they should shoe. Pleasant's answer is that it depends on the intended use of the horse. According to Pleasant, shoeing protects the hoof from excessive wear that possibly could cause lameness. He also said that some horses don't need to be shod because of the excessive growth rate of the hooves. Many farriers and veterinarians work together on shoeing in order to treat abnormalities in the limb.
Pleasant says no nails should be placed beyond the widest part of the horse's hoof. By doing this, the hoof still can contract and expand the way it's designed in order to absorb the shock of its hitting the ground. The shoe sticks out beyond the hoof, but the hoof will grow into the shoe in about six weeks' time.
Environmental factors that affect the condition of the hoof are urine, manure, and repeated wet/dry conditions. Urine and manure provide the perfect growth medium for bacteria that can erode the hoof walls, according to Pleasant. Repeated wet/dry conditions cause the hoof to expand and contract continually, which gives bacteria ample opportunity to enter into the hoof wall and cause damage.
Pleasant's comment on thin walls and soles is that thin soles bruise easily and can cause shoeing problems because shoes can't be nailed on safely since sensitive tissue could be penetrated.
Under-run heels are a problem with some horses since this condition robs the horse of support. As a final comment on under-run heels, Pleasant said, "As a horse owner, be patient with your farrier when he's trying to correct under-run heels because you have got to get the hoof growing first, and that will take time."
Tracy Turner, DVM, gave the audience a lesson on thermography. According to Turner, thermography measures the temperature of the skin and lets you know what is going on under the skin's surface. However, Turner added, it's only a diagnostic tool to find out the location of the "hot" area. Further tests are needed to diagnose the problem.
Thermography does provide a non-invasive practical aid in diagnosis. It's commonly used in pre-purchase exams, saddle fitting, hoof balancing, in checking feet to see if any parts of the hoof are being stressed, and as a training aid in order to prevent injuries.
According to D. S. Kronfeld, BVSc, the nutritional goals the horse owner should try to achieve with his horse depend on the type of horse and the type of work the horse is performing. Kronfeld said the broodmare has the toughest task of all horses. Spend plenty of time on her nutritional needs since you are actually taking care of two horses.
If there are nutritional problems, the first thing Kronfeld does is inspect feces samples from horses in the facility. The condition of the feces tells a lot about the diet of the horses.
If the horse is experiencing weight loss, the following five things should be checked:
The content of the GI tract -- this is easily corrected in a matter of days.
Water loss -- easily corrected within a few hours.
Fat loss -- more tricky, might take a few weeks to restore.
Protein loss -- difficult to correct and will take two to three months.
Bone mineral loss -- very slow to correct, will take several months.
To see if the horse's energy needs are being met, owners need to consider body weight, body condition score, temperature, pulse, respiration, and the activity of the horse.
Emaciation, according to Kronfeld, has many causes, including bad teeth, bad feet, bad feed, or a deprivation of energy. On the other hand, an overweight horse is almost certainly caused by overfeeding. Kronfeld said nutritional support of sick horses is vital because when a horse is ill, it goes into a fasting phase, which causes it to lose weight suddenly. This phase is called hyper metabolism. In these cases, it's important to increase nutrition to the animal because fever and other body systems are making the horse's metabolism speed up and expend calories. In these cases, protein is mobilized rapidly along with fat.
David M. Nunamaker, VMD, presented a study titled "Adaptation of the Third Metacarpal Bone to Growth and Superimposed Training in the Thoroughbred Racehorse." The study focused on metacarpal stress, or bucked shins, that the horse experiences during race training. Nunamaker's hypothesis was that high strain cyclic fatigue causes decreased bone stiffness in vivo, just as it does in vitro.
According to Nunamaker, "Revised training regimes are designed to decrease the number of high-strain cycles, which at the same time introduce the bone to the environment in which it must survive."
About the Author
Tim Brockhoff was Staff Writer of The Horse:Your Guide to Equine Health Care from 1995 to 1999. His degree is in Agricultural Communications from the University of Kentucky, and his equine experience is with American Saddlebreds.
POLL: Radiographs for Hoof Care