Is your horse getting a balanced range of essential and non-essential amino acids from their feeding program? Your horse needs adequate amino acids in their diet to make proteins.

Proteins are complex molecules that are required for almost every physiological function including muscle contraction, neural communication, metabolism of sugars and fats, immune responses and more.

Suboptimal protein or amino acid levels in the diet can cause a broad range of symptoms in horses including:

  • Loss of muscle mass
  • Poor growth
  • Slow recovery from illness
  • Poor performance
  • Rough coat
  • Weak hooves

These signs are not exclusive to protein deficiency and could also occur when energy needs are not met or with vitamin and mineral deficiencies. A diet evaluation complete with a hay analysis is the best way to determine whether your horse is getting adequate amino acids from their feeding program.

Does Your Horse Need More Amino Acids?

Young, growing animals are most susceptible to amino acid deficiency because they have a higher demand for protein to support their rapid growth. Protein requirements are also higher in mares during late gestation and early lactation to support optimal fetal growth and milk production.

Horses, like all animals, can not store excess amino acids to use at a later time. Protein must be continuously supplied by the diet. However, feeding too much protein is not only expensive, but can cause unnecessary strain on the liver and kidneys.

Senior horses, those under heavy exercise, and horses with metabolic concerns should have their protein intake carefully assessed to avoid oversupply.

Some amino acid supplements might be useful to horses if their diet is lacking in a particular amino acid. Lysine, threonine and methionine are the most commonly deficient amino acids in equine diets.

Ensuring their requirements are met will support optimal protein synthesis for overall health of the horse.

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  • Optimal protein synthesis
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Amino Acid Nutrition in Horses

When an equine nutritionist balances the protein content of your horse’s diet, they will pay close attention to whether it is meeting individual amino acid requirements.

Horses do not absorb intact proteins from the diet. Instead, the proteins in forages, grasses, and grains, are broken down by enzymes in the small intestine.

The individual amino acids or small peptides (short chains of 2-3 amino acids) are subsequently absorbed into the blood. These are used by all cells of the body to make the proteins your horse requires.

Proteins can only be made if all the necessary amino acids are available. If not, the body will break down other proteins to supply the required amino acids which can have negative health consequences.

Rate limiting amino acids are those that are most often supplied in the diet in the lowest amount relative to what a horse requires. This concept is commonly exemplified by the analogy of a barrel with staves of different heights. The barrel will only hold as much water as the lowest stave will contain. Similarly, a horse will only make as much protein as the first rate limiting amino acid can support.

Types of Amino Acids

There are 21 amino acids that are used to make proteins in horses. These all have a similar chemical structure, but differ in the arrangement of atoms in a part of the molecule referred to as the amino acid side chain.

Amino acids can be broadly divided into three categories:

  1. Essential: 10 amino acids that must be provided in the diet because they can not be made in the body (endogenously).
  2. Non-essential: Amino acids that can be made from amino acids or other compounds in the body and do not need to be supplied by the diet.
  3. Conditionally essential: Amino acids that might be necessary in the diet because their supply can not keep up with demand under certain circumstances such as rapid growth or illness.

Below we will review the roles, sources, symptoms of deficiency and excess, and requirements for each amino acid. We also evaluate the amino acid profile of various protein sources.

Before making changes to your feeding program, you can submit your horse’s diet for analysis online and one of our equine nutritionists will help you review your horse’s needs.

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Essential Amino Acids

The 10 amino acids that must be supplied by the horse’s diet are:

  • Lysine
  • Threonine
  • Methionine
  • Tryptophan
  • Leucine
  • Isoleucine
  • Valine
  • Histidine
  • Phenylala