Effect of Different Patterns of Excess Amino Acids on Performance of Chicks Fed Amino Acid-deficient Diets

Abstract

Two assays were conducted to determine the effects on chick growth of individual amino acid deficiencies. Deficiencies of phenylalanine-tyrosine, tryptophan or isoleucine impaired growth more than equal deficiencies of other amino acids. In assay 2 individual amino acids were held at 60% of the chick requirement and were compared with a total deficiency of amino acids wherein all amino acids were reduced to 60% of the chick requirement. Compared with total amino acid deficiency, weight gain was a) increased by individual deficiencies of methionine-cystine, leucine, lysine or arginine, b) not affected by a deficiency of histidine and c) decreased by deficiencies of phenylalanine-tyrosine, tryptophan, isoleucine, valine or threonine. Utilization of the deficient amino acid was greater when that amino acid alone was deficient than when all of the other amino acids were reduced to a comparable level of deficiency. Compared with the complete amino acid diets, food consumption was reduced when individual amino acids were made deficient but not when all amino acids were made deficient simultaneously. The pattern of amino acids in excess of that needed for growth appeared to dictate whether an amino acid imbalance would be superimposed on that of an amino acid deficiency.