Protein and Amino Acids in the Equine Diet

Protein and amino acids are necessary in the equine diet, especially for hard-working horses.
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In general, mature, working horses need 10-12% protein in their diets, with slightly higher amounts necessary for horses in hard exertion.

Protein is comprised of various amino acids—some are synthesized by the horse and others are essential amino acids that must be supplemented through dietary intake. Protein is critical to maintain and repair tissue. 

In general, mature, working horses need 10-12% protein in their diets, with slightly higher amounts necessary for horses in hard exertion. Alfalfa or legume hay provides high-protein content forage—up to 20%—to the diet. Grass hay provides 5-15% protein. Cereal grains such as oats, corn and barley provide 9-13% protein, but these don’t tend to provide essential amino acids. Balancer pellets can provide up to 30% protein and should be fed when needed.

Feeding too much protein is counterproductive for an equine athlete because it increases water needs and increases internal heat generated through metabolism. In addition, it results in extra ammonia production excreted in the urine, which can lead to respiratory issues in horses stalled indoors for long periods. Consult with your veterinarian regarding correct protein levels to feed each horse.

Amino Acids

Exercise conditions muscle, but it does not "make" muscle. Building strong muscle necessitates dietary intake or supplementation of all 10 essential amino acids:

  • Lysine – for growth, particularly important for young horse growth
  • Threonine – for older horse repair and maturation
  • Methionine – for hoof and hair
  • Valine, Leucine, and Isoleucine are branch chain amino acids (BCAA) important for muscle recovery
  • Phenylalanine
  • Tryptophan
  • Histidine
  • Arginine

To facilitate muscle repair and recovery, nutrients used up in work should be added to the diet. A well-balanced diet includes added amino acids for muscle support. 

Researchers recommend that fast recovery is best achieved when amino acids are supplied within 45 minutes following exercise. 

Adding amino acids to the diet is shown to reduce muscle breakdown and improve muscle synthesis in humans, with the addition of branch-chain amino acids further enhancing positive effects. 

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