The Phenylalanine and Tyrosine Requirements and Their Interrelationship for the Young Chick

A purified crystalline amino acid diet was used to study the phenylalanine tyrosine interrelationship in young chicks. Dietary phenylalanine and tyrosine requirements for maximal growth were observed to be 0.50±.07% and 0.37±.05%, respectively. Tyrosine was thus capable of furnishing up to 42.5% of the total requirement for aromatic amino acids. Under dietary conditions of phenylalanine adequacy and tyrosine deficiency, phenylalanine was found to be equal in efficacy to tyrosine in providing the limiting nutrient, tyrosine. Efficient molar conversion of phenylalanine to tyrosine was observed.