Effect of Different Proteins and Protein Levels on the Glycine Need of the Chick Fed Purified Diets

THE glycine requirement of the young chick was reported by Almquist and Mecchi (1942) to be 1.5% of the diet when glycine was furnished by free amino acids and only 1.0% when glycine was supplied by a protein such as gelatin. Wietlake et al. (1954), using casein diets, were unable to demonstrate that supplemental glycine significantly improved chick growth. A glycine requirement in excess of 1.5% of the diet was suggested by Fisher et al. (1955), for both purified and practical diets for optimal growth and feed efficiency of fast-growing chicks. Klain et al. (1960) reported that a dietary requirement for glycine could not be demonstrated with a synthetic amino acid diet even though the diet was devoid of serine. However, Greene et al. (1960) using an improved amino acid mixture, capable of supporting better growth, noted that growth, feed utilization, and nitrogen retention improved with each increment of glycine…