Amino Acid Deficiencies of Casein as a Source of Protein for the Chick

Abstract

A synthetic diet which contained 35% of casein and 0.5% of methionine was supplemented with arginine, glycine and creatine. When these were added singly the improvement was slight with 1.5% of glycine, and large with 0.5% of arginine or with 1.5% of creatine. When the rations were deficient in arginine the feathers were imperfect and some of the chicks had an abnormal gait. Weights of the same order of magnitude were obtained with arginine alone and with combinations of arginine and glycine, glycine and creatine, and arginine and creatine; also with a combination of 25% casein and 10% gelatin. The range in weight and the standard deviations of the weights indicated that all of the rations previously mentioned were in some degree inadequate. When casein alone was supplemented with 0.5% arginine, 1.5% glycine and 1.5% creatine simultaneously, the average weight of the chicks was exceptionally high for White Leghorns, the feathers were excellent, and there were no cases of abnormal gait. When the amount of arginine was increased to 1.24% and creatine was omitted, there was no reduction in the average weight. A combination of 25% casein and 10% gelatin was partially inadequate as a source of protein for the chick.