Effect of Excess of Individual Essential Amino Acids in Diets on Chicks

Abstract

Excesses of single amino acids given in the diets of chicks from day 8 to day 18 depressed growth and food intake to varying degrees, which were dependent on the kind of amino acid supplemented. L-Methionine and L-phenylalanine caused the severest growth depression. L-Tryptophan, L-threonine, L-lysine, L-histidine, L-tyrosine and L-leucine were apparently toxic. All other amino acids tested, L-arginine, glycine, L-valine, L-cystine and L-isoleucine, showed no or only a slight effect.
An increase in the blood plasma concentration of the amino acid in dietary excess was observed, and the possible existence of a branched-chain amino acid antagonism was suggesested in chicks.