Horses need muscle to support and move the skeleton and protect joints, tendons and ligaments. In addition, working horses will use these muscles to support the rider and perform the athletic tasks required.
Muscles are predominantly made from the building blocks of protein called amino acids. There are some amino acids that the horse can produce for himself and others, called essential amino acids, which he must receive from his diet. There are 9 essential amino acids, and research has indicated that there are at least two which are particularly important for muscle development – Lysine and Leucine.