Arginine Requirement of the Chick and the Arginine-Sparing Value of Related Compounds

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Abstract
Male White Leghorn chicks were reared to 4 weeks of age on a basal, purified diet that contained 35% of casein and 10% of soybean oil. The diet, which contained by analysis 1.2% of arginine, was supplemented with 0.5% of methionine and in some cases with glycine. Graded levels of arginine, creatine, guanidoacetic acid and glycine were added as supplements. Under these conditions, the arginine requirement for maximal growth without added glycine was 2.25% and with 1.5% of added glycine it was 2.1% of the diet. When the basal diet contained 1.2% of arginine, creatine spared about 0.4% of arginine and 1% creatine was as effective as higher levels. When the basal diet contained 1.5% of arginine, about 0.3% of arginine was spared by 0.5% of creatine, and when it contained 1.8% of arginine, 0.25% was spared by 0.3% of creatine. Creatinine spared slightly less arginine than creatine, and guanidoacetic acid spared about one-half as much. When the arginine level was suboptimal, 3.0% glycine supported a faster rate of gain than 1.5% but not when adequate arginine or arginine plus creatine were present. When sufficient arginine and insufficient glycine were present, creatine improved the growth rate and thus may be said to spare the glycine requirement.