May 21 , 2021
There are three branched-chain essential amino acids in the body of horses. These are Leucine, Isoleucine and valine. As an essential amino acid, an adequate quantity of leucine is compulsory in the diet of horses to fulfill the body's needs. Leucine and other branched amino acids are obtained from plant proteins. A large amount of leucine is present in horse feed. It is also present in oats, corn, and soybeans. During digestion, pancreatic enzymes hydrolyze the protein, and leucine is produced which is essential for the proper growth of young horses.
Like in human physiology, leucine and lysine are the most abundant amino acids present in the muscles of equines. A large amount of leucine is present in skeletal muscle. It is used to make new proteins in a horse’s muscles. It also burned as an energy source during exercise. Leucine stimulates protein synthesis by activating the enzyme mTOR. It helps repair and build muscles.
The horse body uses leucine as a source of gluconeogenesis during starvation, infection, stress, and recovery from trauma and surgery to promote the healing process. It is converted into alanine which is used in the liver to make glucose. In this way, leucine maintains the glucose level of the horse during exercise and backs up the muscles during hard activities. If leucine is given after exercise, it stimulates the secretion of insulin which restores the glycogen level of muscles, depleted during exercise.
Leucine is also involved in the production of hemoglobin which is a red blood cell protein that binds oxygen and transports it to various tissues of the body along with muscles. Leucine is also converted to HMG-Coenzyme A, a precursor of cholesterol that is involved in maintaining healthy cell membranes. HMG-CoA is also involved in the production of ketone bodies which acts as a source of energy during horse exercise.
Leucine is a part of enkephalins which are opioid-like compounds that act as painkillers. Leucine maintains nitrogen balance in adult horses. It is recommended that 10 grams of L-leucine with sugar after exercise helps in rapid exercise recovery and in rebuilding glycogen stores. It is especially recommended for frequent muscle soreness and poor topline horses.
Deficiency of leucine limits exercise ability causes early fatigue in exercise. It also causes poor quality hair and hoof growth in horses and sometimes results in weight loss. Excess of leucine disturbs vitamin B3 production in the liver and alters the normal body functioning of horses.
Horses normally get sufficient leucine from diet but athletic horses must be provided with leucine supplementation to avoid complications and ensure normal activity of horses.