Amino acids (AA) are the building blocks of all proteins and are essential for a number of physiological functions within the equine body.

Kristine Urschel, PhD, associate professor of animal science at the University of Kentucky, in Lexington, shared the functional importance of AA and protein in exercising horses during the University of Maryland’s Department of Agriculture and Natural Resources’ 2016 Mid-Atlantic Nutrition Conference, held March 23-24, in Hunt Valley, Maryland.

Horses’ bodies are mostly made of muscle, which makes up 40-55% of their body weight. Muscle contains roughly 70% water, 20% protein, and 10% fat, glycogen, vitamins, and minerals. Proteins comprise the bulk of solid skeletal muscle, and therefore are of particular interest in exercise physiology, Urschel explained

Exercise increases muscle protein “turn over,” meaning the body breaks down and re-synthesizes protein—an important cycle for building muscle. “However, the process is not uniform throughout the body,” Urschel said “The effects of exercise on plasma AA concentrations have been well-studied, but the implications are varied.”

Plasma AA concentration is only snapshot of every internal process at any given moment in time, so it’s difficult to determine exactly where a change might have come from, she explained In general, an increase of essential AAs in the plasma could mean increased protein breakdown, and a decrease in essential AAs could indicate that the AA is being broken down for use as energy source.

How Much Protein?

There has been some controversy