Building Muscle Mass: Researchers Study Protein's Role

Researchers are always working to better understand the equine body and how it functions. Case in point: A team of researchers from the Virginia Tech Middleburg Agricultural Research and Extension Center recently completed an index study on a high-protein diet's relationship to increased muscle synthesis in horses. A better understanding of what happens at a molecular level in the horse's body will help scientists design future studies for examining dietary management practices.

Scientists know the main structural component of muscle is protein, and dietary protein provides the horse's body with amino acids, which are the basis for formation and repair of muscle and other soft tissues throughout the body.

But, researchers had never examined dietary protein's effect on the stimulation of muscle protein synthesis in horses. Kristine L. Urschel, PhD, now an assistant professor in Animal and Food Sciences at the University of Kentucky, and a team of researchers examined muscle protein synthesis in horses fasted for 18 hours (to reduce the levels of amino acids present in their bodies).

The team withheld feed from eight healthy mature horses (9 to 17 years old with no known medical conditions) for 18 hours before taking blood samples. They then offered half of the group a 33% crude protein feed at 2 g/kg of body weight while the other horses served as controls and continued fasting.

At 90 minutes post-feeding research team members took and analyzed blood samples and a tissue sample from the middle gluteal muscle (a large muscle located in the horse's hind end) of each horse in the study, along with a blood sample from each horse, examining each for evidence of increased protein synthesis.

Upon reviewing test results, the researchers found that the horses consuming the high-protein diet had higher amino acid levels in their biopsy and blood samples. When they examined measurements of factors in the muscle that are necessary for protein synthesis, they noted evidence of an increase in protein synthesis in these horses as compared to those that did not consume the high-protein feed.

"This study gives us baseline data in mature, healthy horses and will pave the way for future studies in growing and 'old' horses to see how protein synthesis is affected in animals that are actively gaining (growing horses) and losing ('old' horses) muscle mass," Urschel said.

Urschel explained that this study and future studies like it will aid researchers and veterinarians in determining which type of diet is most efficient in optimizing muscle development.

"This study was the first step toward understanding (what) controls muscle protein metabolism in horses," she said, "but there is still a lot of work to be done before we can translate any of this into improved feeding or management recommendations.

"This study was ... a tool to learn more information about how muscle works so that eventually we can do more applied research," she concluded. "This is literally the first step."

The study, "Effect of feeding a high-protein diet following an 18-hour period of feed withholding on mammalian target of rapamycin-dependent signaling in skeletal muscle of mature horses," was published in February in the American Journal of Veterinary Research. The abstract is available on PubMed.

About the Author

Marie Rosenthal, MS

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