High-speed treadmills help take some of the guesswork out of assessment of nutrientsThe development of the relatively inexpensive and reliable high-speed treadmill (HST) has allowed equine exercise physiology and nutrition research to be conducted outside of university settings. This, along with affordable heart rate monitors, lactic acid, and other blood analysis equipment, has also facilitated experiments not possible 20 years ago.
The ability to conduct such research has become an important adjunct to the nutritional studies carried out at Kentucky Equine Research. KER was initially founded, President Dr. Joe Pagan notes, "to disseminate the results of nutritional and exercise research being performed at the universities, to the farms and feed manufacturers who could most benefit from the application of this information."
In addition, Pagan, along with Dr. Stephen Jackson, was interested in continuing his own research. The two began with digestion trials, where all of the manure and urine was collected from horses fed specific diets. The collected material was then analyzed to determine how much and which nutrients were actually consumed, and which were not. Though tedious, this type of study is vital to determine how nutrients are used by the horse.

Step test
It was the addition of their new HST facility and adjacent laboratory that allowed KER to follow up on questions posed by their clients. The primary advantage of the HST is the reproducibility of training and testing as opposed to what can be accomplished on the track. There is never a day the rider does not come in or a day lost to bad weather, and the exercise can be controlled with a precision that no exercise rider can duplicate. "If the protocol calls for a half-mile trot," Pagan explains, "followed by a mile gallop at 20 mph followed by another half-mile trot, we can do this accurately time after time."
The HST also reduces injuries, which, in turn, preserves the group being tested. "When we tried to conduct field trials at the track," Pagan notes, "we sometimes lost horses to injury as quickly as O. J. jurors. And, just like a legal trial, you need a minimum number of participants or the results are just not valid."
But it is during actual testing that the HST really is invaluable. The step test consists of a two-minute walk followed by a half-mile trot. The horse is then galloped a half-mile at four different speeds. Heart rate is measured throughout the test and recorded at the end of each step. In addition, blood samples are drawn through a jugular catheter at the end of each step and analyzed for lactic acid accumulation, as well as other metabolites of exercise. Again, it is the ability to precisely control the exercise that makes the experiment valid. If an effect of a given nutrient on performance is being tested, then the step test will be done at least twice. For one test the nutrient will be fed for a given period (two weeks to a month, typically), while a prescribed exercise protocol is followed. Then the horse is given a step test. The nutrient is then removed from the diet for a similar period, although all other factors, including the exercise protocol, are repeated. The step test is performed again. It is the comparison of the heart rate, lactic acid, and other test data that determine if the nutrient had an effect, had no effect, or was deleterious to performance.

Enter chromium
KER became interested in the possible performance implications of chromium in the horse. Although chromium has long been known to be an essential human nutrient, there was no research on its importance in horses. In species that had been studied, chromium was found to enhance the affinity of the body to bind insulin. Since insulin acts to direct nutrients to target tissues, it is thought that chromium can enhance the uptake of amino acids and glucose by the body. Recent swine studies had found that additional dietary chromium results in increased muscle growth and reduced fattening. So KER sought to determine if chromium would have any effect on performance in the horse.
Six Thoroughbreds who had been in training before the experiment began were used. They were divided into two groups, with three receiving a ration of eight pounds of sweet feed, five pounds of orchard grass hay, and six pounds of AlfaOats, a pellet from Canadian Agra Bio-Cube that is made from a combination of alfalfa and whole oat plants. The other three horses received the exact same ration, along with five milligrams per day of chromium contained in a chromium yeast product (Co-Factor III [Alltech, Inc.]). Each group was fed this ration for two weeks and tested, then the rations were reversed for another two weeks and the tests repeated. This design is meant to eliminate any effects that might occur due to training (although, in practice, once horses are fit, additional training has little effect on their test scores).

And the winner is
Normal lactic acid accumulation is considered a contributing factor to fatigue during strenuous exercise. Typically, as a step test progresses, lactic acid levels increase, peaking after the last step. But, in the case of the chromium-supplemented horse, peak levels were significantly lower than the unsupplemented horses. This is thought to be beneficial to the performance horse.
In addition, another hormone that was measured, cortisol, was significantly lower in the horses fed chromium. Since cortisol is normally produced in response to stressful situations (such as training), this was also seen as a beneficial effect of chromium supplementation.
So is chromium a new essential equine nutrient? "An important factor in determining if your horse will respond to chromium supplementation," Pagan explains, "is whether it is chromium deficient. Strenuous exercise and high-grain diets increase the excretion of chromium into the urine, so horses in heavy training are likely candidates. Rapidly growing horses that are fed high-grain diets are also likely to benefit, but not the mature, sedentary horse. But chromium also seems to reduce the incidence of tying up. Further research is needed here, but it is clear that chromium is important in certain groups of horses."

More product information
There are a whole host of products that are purported to improve performance in the horse. As yet, few have been subjected to the type of experiment that demonstrate that their claims of being "ergogenic" or performance-enhancing are valid.
Lactic acid is a normal by-product of exercise, its production usually linked to increasing fatigue. As horses become fit, they will produce less lactic acid (to the plateau we call dead fit) for a repeated exercise event. Run a horse a half-mile on the track (or treadmill) at 18 mph every other day for two months and the lactic acid levels at the end of exercise will fall.
As a result, lactic acid can be used to compare relative fitness between two individuals, all other factors being equal. Or you can change one factor, say, add a product that claims to "improve" performance, and see if lactic acid levels do, in fact, change. This is what researchers at the University of Kentucky recently did to test the ergogenic performance of a chemical known as trimethylglycine (TMG). Eight mature, untrained Thoroughbreds (five geldings and three mares) were randomly assigned to either receive TMG or be part of the control group. Those that were in the TMG group would be fed 80 mg/kg of their body weight as a top dressing on their feed daily. Both groups were trained and conditioned on a high-speed treadmill. After a 60-day period, both groups were given an exercise test where plasma lactate levels (along with glucose, free fatty acids, and triglyceride levels) were measured during and after testing. The groups were then reversed, with the original control group now receiving the TMG supplement. The two groups were exercised again for 60 days and the tests repeated.
Unfortunately for all of us who would like to be able to feed a product that would shorten the time it takes to get a horse fit, the TMG group did not have lower lactate levels than the control group. If there are advantages to this type of product, they were not revealed for this amount of TMG fed this way and tested by this protocol.