Arginine and Creatine Interrelationships in the Chick

Studies were conducted to evaluate the possible role of creatine synthesis in variations of the arginine requirement of chicks. Chicks of a high (HA) arginine requirement strain grew poorly and had lower liver transamidinase activity than chicks of a low (LA) arginine requirement strain when fed an arginine-deficient diet. Supplementation of the diet with arginine eliminated the strain differences. Although liver transamidinase activity was lower for chicks of the HA strain when the arginine deficient diet was fed, supplementation of the diet with creatine failed to eliminate the difference in growth rate between chicks of the two strains. Variations in the rate of creatine synthesis, therefore, appeared to be of minor importance in hereditary variations of the arginine requirement of chicks. A study of creatine plus creatinine excretion revealed that the daily excretion of creatine plus creatinine represented on a molar basis less than 5% of the arginine consumed when chicks were fed an arginine-deficient or -adequate diet. The growth response to dietary creatine for both strains of chicks was maximal when creatine was added to the diet at a level equivalent on a molar basis to 5% of the dietary arginine. This response was similar to that obtained when the diet was supplemented with an equivalent amount of arginine. It is concluded therefore that the effect of dietary creatine on growth can be attributed solely to sparing of arginine otherwise used for creatine synthesis.