Lysine is the first-limiting amino acid in corn-soybean diets for swine and second limiting, after Methionine, in poultry.

Corn, which comprises the largest portion of monogastric diets, is low in lysine. In order to meet the amino acid requirements of swine and poultry, high-protein ingredients such as soybean meal and animal by-product meals are blended with corn. In the past, excess protein was fed to meet the requirement of the first limiting amino acid. With the commercialization of L-Lysine, nutritionists have more flexibility with utilizing nontraditional feed ingredients, which may improve profitability without loss of feed quality. As a result, the lysine requirement of livestock can be met in a cost-effective manner by reducing the amount of costly, high-protein ingredients that were once fed.