Arginine

Arginine (Arg) is a conditionally essential amino acid in foals, young growing horses, pregnant mares, or during recovery from an illness, infection or traumatic injury. Arginine is physiologically active in the L-form (L-Arg) and participates in protein synthesis in cells and tissues. Arginine is important for blood flow, the urea cycle, and nitric oxide levels. There is evidence that long-term usage influences release of hormones.

When horses are receiving excessive levels of the amino acid lysine, or not enough protein in their diet, they have an increased risk of arginine deficiency. Arginine deficiency in horses can impair insulin secretion, liver lipid metabolism, and glucose production. Horses may show signs of muscle weakness, hair loss, poor quality mane and tail hair that easily breaks, prolonged wound healing, and liver damage.

Supplementing a horses diet with l-arginine has been shown to alter the absorption of other amino acids in mares. High doses of l-arginine can cause gastrointestinal upset preceding diarrhea.