The Isoleucine Requirement of Weanling Swine Fed Two Protein Levels

Abstract

Three experiments were conducted with weanling pigs to measure the isoleucine requirement and its relation to the dietary protein level. A synthetic diet containing soluble blood flour supplemented with methionine was used as an isoleucine-deficient diet and was calculated to contain 88% total digestible nutrients. Supplementary L-isoleucine was added as a 32% concentrate with D-alloisoleucine as the remainder. With a diet containing 13.35% protein the maximum rate and efficiency of gain were obtained with a minimum level of 0.46% L-isoleucine, equal to 3.4% of the dietary protein. On the other hand, with 26.70% protein the maximum rate and efficiency of gain occurred at a minimum level of 0.65% L-isoleucine, equal to 2.4% of the dietary protein. The L-isoleucine need in the high- and low-protein diets was 0.74 and 0.52% of the total digestible nutrients, respectively. Assuming a linear relationship between dietary protein and isoleucine requirement, expressed as a percentage of the protein, the isoleucine need within the protein range studied may be expressed by the equation, Ŷ=4.5−0.076X, where Ŷ is the isoleucine need and X is the percentage of dietary protein. Copyright © . .