Large complex molecules comprising single or multiple chains of amino acids. An essential part of all living tissues such as muscle and nerves they are also needed for antibodies and enzymes – nothing in the body happens without the involvement of proteins.
Protein molecules are too large to pass through the gut wall so dietary protein must be broken down into amino acids and peptides by enzymes called proteases and by bacterial fermentation, principally in the hind gut, to permit absorbtion. The component parts are re-assembled into proteins in the liver and other tissues. There is a continuous turnover of proteins in the body with scavenging of their amino acids to build new proteins. All proteins are based on Nitrogen and if the protein supply from the diet is less than requirements then the body is said to be in a negative Nitrogen balance and will begin to source protein and amino acids from it’s own tissues, mainly muscle tissue. If the protein deficiency continues, muscle wasting will result.
For horses, protein quality is important, especially in young growing stock and horses undergoing strenuous exercise where protein demands are high for tissue growth and repair. The ammino acid profile varies between protein from different sources and the amino acid Lysine is used as a guide to quality as it is the first limiting amino acid for growth and repair. Feeds with good Lysine levels include soybean, lupin, and Lucerne. Both protein and Lysine requirements for all the different classes of horse have been established and can be found in the reference publication ‘’Nutrient Requirements of Horses” NRC
Traditionally high protein diets have been blamed for making horses ‘’fizzy’’ but in fact it is energy, not protein which is the most likely culprit in that respect.