Lysine, Methionine and Tryptophan Supplementation of a Corn-Meat and Bone Meal Diet for Growing Swine

Abstract

Sixteen lots of four crossbred pigs (two barrows and two gilts; two lots per treatment) averaging 20 kg initially were used to determine effects of lysine, methionine and tryptophan supplementation of corn-meat and bone meal diets for growing swine. Supplementation with 0.25% L-methionine or 0.20% L-lysine, alone or in combination, did not affect ADG, G/F or PER of pigs fed the corn-meat and bone meal diets over a 42-day experimental period. Inclusion of 0.10% added L-tryptophan, alone or in combinations with L-lysine and DL-methionine, significantly increased ADG, G/F and PER. Tryptophan and methionine supplementation, alone and in combination, increased concentrations of the corresponding free amino acids in the plasma regardless of lysine supplementation. Plasma free lysine increased with lysine supplementation, alone or with methionine. However, inclusion of added lysine with tryptophan, or tryptophan and methionine, did not result in greater levels of free lysine in plasma than obtained from feeding the basal diet. Plasma free lysine was decreased due to supplementation of the diet with tryptophan, alone or with methionine, and was associated with increased rate of gain. Also, as rate of gain increased with tryptophan supplementation, levels of free isoleucine, phenylalanine and especially threonine in the plasma decreased. Tryptophan was the first-limiting amino acid and based on plasma free tryptophan levels less than 0.10% supplemental tryptophan apparently was adequate to supplement the basal diet adequately. Concentrations of free lysine, isoleucine, phenylalanine and threonine were indicative of borderline adequacy or lack of total availability of these amino acids while methionine appeared to be adequate.