Amino acids and proteins in the horse

In mammals, there are 21 different amino acids known. These amino acids can be partially synthesized by the horse itself (non-essential) amino acids. There are also some amino acids that the horse needs to obtain through diet (essential amino acids). Additionally, there is a "gray area" with a number of amino acids that are non-essential, but in some cases (for example, during illness) become essential.

Proteins are chains of amino acids that are linked together by peptides.

Function of amino acids and proteins in horses:

Spine building
Energy metabolism
Various metabolic processes

Groups of amino acids

9 essential amino acids in mammals: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
6 non-essential amino acids: alanine, asparagine, aspartate, glutamate, serine, and selenocysteine
6 "gray area" amino acids: arginine, tyrosine, glutamine, cysteine, glycine, and proline.

What are proteins?

Multiple amino acids linked together by peptides form a protein. Proteins are essentially just proteins.

15% of body weight consists of proteins, with muscles containing the majority. Proteins provide structure, regulate the transport of nutrients through the blood, regulate metabolic processes, are a component of the immune system, and act as a buffer to maintain stable pH in the body.

Function of amino acids

Some amino acids, in addition to being part of proteins, also have a physiological role in the body. Glutathione (cysteine, glycine, and glutamine) have antioxidant properties. Creatine (arginine, glycine, and methionine) is involved in cellular energy metabolism. Carnitine (lysine, methionine) is involved in the transport of fatty acids through cell membranes. Carnosine (histidine and alanine) is present in high concentrations in the skeleton to buffer lactic acid. Virtually all amino acids also have an independent role in the body.

Digestion of proteins/amino acids

Proteins cannot be directly absorbed in the intestines; they must first be broken down into individual amino acids and peptides. Protein breakdown begins in the stomach by enzymes in stomach acid. These enzymes break down the structure to allow digestive enzymes better access. In the small intestine, along with enzymes from the pancreas, proteins are further broken down into smaller pieces. The broken-down amino acids and peptides are largely absorbed in the small intestine. Undigested proteins and amino acids that have not been absorbed are broken down and absorbed by bacteria in the large intestine. Ammonia remains as a by-product.

To be absorbed from the intestines into the bloodstream, amino acids require a transport system that helps them pass through membranes. Nitrogen plays a crucial role in this process.

Important protein sources

Milk, colostrum contains 10-19% crude protein, and then it stabilizes at 2% in milk. This is a high-quality protein; after 2-3 months, the foal obtains most of its protein from other sources.
Roughage: a good source of protein but varies greatly in quality and quantity. Herb-rich roughage has a higher percentage of protein than roughage consisting almost entirely of grass. The younger the grass, the more protein it contains.
Concentrate feed: concentrate feed and grains are relatively high in protein, depending on the type and quality.

Special amino acids commonly found in supplements

Methionine: keratin is a protein that is the main component of hoof horn and is rich in the amino acids methionine and cysteine. For this reason, methionine is often added to hoof supplements. However, there is no scientific evidence that this has a positive effect on horse hooves.
Tryptophan: tryptophan is added to many calming supplements due to the role it plays in the neurotransmitter serotonin. Serotonin levels are associated with sedation (high levels) and aggression/fear with low levels of serotonin. Studies have shown that oral administration of tryptophan does not have a calming effect on horses, while a high dose administered intravenously does. Therefore, administering tryptophan as a calming supplement may not be effective.

Deficiency or excess?

Symptoms of amino acid deficiency include: lethargy, poor appetite, weight loss, poor hoof and coat condition. Deficiencies are not common, usually limited to a deficiency in a particular amino acid. Most diets provide a healthy horse with the right amount of amino acids. Feeding an excess of amino acids has no benefits for the horse and can be excreted in the urine, causing additional stress.