Effect of Single Amino Acid Excesses on Glucose Metabolism and Chick Growth, as Influenced by the Dietary Amino Acid Balance

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Abstract
Experiments were conducted to determine if the growth depression in chicks caused by feeding a high level of DL-lysine HCl, L-tyrosine, or DL-methionine could be overcome. The growth depression caused by the addition of lysine was proportionally less when zein, corn, or additional gelatin was included in the diet. The growth depression caused by excess tyrosine was also less when additional gelatin was added. These proteins increase the level of other amino acids in the diet and thus appear to provide a more favorable amino acid balance. The growth depression caused by feeding excess methionine was not influenced by adding arginine or gelatin, even though these make a better dietary amino acid balance. The restricted feed intake of these chicks is believed to be largely responsible for the growth depression caused by excess methionine. Chicks fed high and normal levels of various amino acids were subjected to glucose tolerance tests. When the chicks were fed diets high in DL-methionine, DL-lysine HCl, or DL-phenylalanine, the blood glucose level following sugar ingestion did not return to normal as rapidly as occurred when chicks received normal diets or diets high in L-arginine HCl, L-leucine, or glycine.