1Adapted from Shannon and Allee,  with updates from recent research conducted by the authors and summarized in this paper. Ratios are based on NRC  nutrient levels for ingredients. Nutritionists should review their ingredient nutrient values relative to NRC  to apply these ratios to their diets.
5Tryptopan:lysine ratio appears to be increased when the diet contains large excesses of large neutral amino acids (leucine, isoleucine, valine, phenylalanine, and tyrosine). Improvements in pig growth have been observed with Trp:Lys ratios greater than 18%.
6Ratio is at least 60% when high levels of blood meal or cells are included in the diet. Ratio may be lower than 52% when blood cells are not included, but more research is required to verify and to determine the optimal ratio of isoleucine to leucine.