Lysine — Frequently Asked Questions

The one in shortest supply relative to the pattern the animal needs to build protein. Because protein synthesis requires all the essential amino acids in the right proportion, the scarcest one caps how much of the rest can be used, and the surplus is deaminated and excreted as nitrogen. In cereal-based pig and poultry diets, lysine is limiting first.

By allowing total crude protein to be cut. Without supplementation the only way to supply enough lysine is to raise dietary protein, which oversupplies every other amino acid and sends the excess out as urinary nitrogen. Adding crystalline lysine lets protein come down by several percentage points while performance is maintained, so less nitrogen is excreted.

Most commonly L-lysine monohydrochloride at 78 percent lysine, and also as liquid and sulfate forms at different concentrations. The form determines both the lysine delivered per tonne and the handling, so it must be specified. All commercial feed lysine is produced by bacterial fermentation of a sugar substrate.

Because only the L-form is biologically active. Animals can use L-lysine but not the D-isomer, so a racemic mixture would deliver only half the nutritional value for the same weight. Fermentation produces the L-form exclusively, which is one reason it displaced chemical synthesis routes for amino acid manufacture.