Amino acid requirements of growing chickens.

1. Using 18% protein diets (N times 6-25), consisting mainly of conventional ingredients of known amino acid composition, the amino acid requirements as percentages of diet and of dietary protein respectively for broiler chickens between 14 and 28 d of age were found to be: threonine 0-50-0-52% of diet (2-8-2-9% of dietary protein); glycine 0-48-0-50 (2-7-2-8); valine 0-69-0-71 (3-8-3-9); methionine+cystine 0-58 (3-2); isoleucine smaller than 0-48 (smaller than 2-7); leucine smaller than 1-05 (smaller than 5-8); tyrosine+phenylalanine 1-09-1-12 (6-1-6-2); lysine 0-87 (4-8); histidine smaller than 0-34 (smaller than 1-9); arginine smaller than 0-76 (smaller than 4-2); tryptophan smaller than 0-14 (smaller than 0-78). 2. Values found were in general lower than those determined using diets consisting entirely of purified amino acids and the reasons for this are discussed.