In the equine industry, there is a need for supplements that can improve performance and muscle recovery. Tributyrin and butyrate affect satellite cells and oxidative metabolism in other species. To assess the effects of tributyrin on equine muscle repair, Thoroughbred horses were supplemented tributyrin, and a submaximal exercise test was performed. RNA isolated from the gluteal muscle of horses supplemented with tributyrin had increased myogenin mRNA. Satellite cells isolated from supplemented horses had a higher percentage of proliferating cell nuclear antigen immunopositive cells, indicating tributyrin primed satellite cells to activate. Another experiment was performed to test the effects of tributyrin supplementation on equine muscle metabolism. Horses were fed tributyrin for 30 days while partaking in light exercise training. After the supplementation period, horses performed an exhaustive exercise test. Tributyrin supplementation did not affect performance or measures of oxidative metabolism in the muscle. To measure the effects of butyrate on equine muscle metabolism, Thoroughbred horses were supplemented butyrate for 30 days. At the end of supplementation gluteal muscle from butyrate fed horses had a higher percentage of type IIA fibers. Tributyrin supplementation demonstrated positive effects on satellite cell activation, but failed to increase oxidative metabolism measures. Butyrate did statistically increase the percentage of type IIA fibers, but not oxidative enzyme activity and the modest increase seen would likely not effect performance. Higher doses and longer supplementation of butyrate and tributyrin should be investigated to see if a metabolic shift beneficial to racehorses can be achieved. Furthermore, future research should focus on tributyrin's effects on satellite cells and how supplementation can improve muscle recovery in racehorses.

Thoroughbred racehorses take part in strenuous races that result in exercise induced damage to the muscle. In turn, this resulting damage to the muscle must be properly repaired before the horse can successfully race again. My projects involved finding nutritional supplements to improve equine muscle repair or metabolism. A special cell in the muscle, called a satellite cell is responsible for repairing this muscle damage. Unlike other muscle nuclei, satellite cells have the ability to divide, providing more myonuclei, able to fuse into muscle fibers for repair. In an un-damaged state, satellite cells are lying dormant in the muscle. However, upon stimulus, satellite cells leave their dormant state and become activated. Along with muscle damage, a lot of energy is used during a race. There are two main ways that energy can be made, either without oxygen (anerobic) or with oxygen (aerobic). Aerobic metabolism is able to produce more energy and is fatigue resistant. I supplemented Thoroughbred horse's diet's with two products, butyrate or tributyrin to test their effects on equine satellite cells and muscle metabolism. Ultimately, my research found that tributyrin was able to stimulate equine satellite cells activate after exercise. I also found that butyrate supplementation increased the percentage of aerobic muscle fibers.

Doctor of Philosophy