Why are so many people feeding lysine? Yes, it is an essential amino acid. But it is not going to solve all of your problems.
Let me tell you how muscles are made.
Muscles are made, to a large extent, out of proteins. Proteins are strings of amino acids. The order in which the amino acids are strung together is what makes each protein unique. The ‘recipe’ for putting these amino acids together is encoded in your horse’s DNA. This recipe is copied (in a kind of reverse code) onto a strand of Messenger RNA (mRNA), which leaves the nucleus and travels to the ribosomes where protein synthesis takes place.
The ribosomes match up each set of nucleotides in the mRNA to a matching tRNA, starting at a specific start sequence (like a barcode). The matching tRNA is carrying the amino acid for that specific sequence, which is added to the growing protein.
Eventually, the ribosomes hit a point in the RNA that codes for ‘stop’. This completes the synthesis of the protein.
The important thing to understand here is that, if an amino acid is missing, the ENTIRE process stops. Which results in no protein. Which in turn results in no muscle being built.
Some amino acids can be manufactured by the horse’s body. But some can’t be manufactured and therefore MUST be supplied in the diet. These are called essential amino acids. Essential amino acids for the horse are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
The essential amino acid which is most often missing during protein syntheses is lysine. It is, in other words, the most ‘limiting’ amino acid.
It is for this reason that people are told to supplement with lysine. And yes, it solves the problem of the most limiting amino acid being absent. But, it does nothing for the second most limiting amino acid, threonine. And the third and fourth, etc. Protein synthesis is still in danger of being stopped.
A much better idea is to supplement the entire range of essential amino acids. This can be done by feeding good quality protein (not too much please) or a good supplement.