Influence of dietary supplementation of arginine or glycine on the adverse effect in chicks given a tyrosine excess diet.

Abstract

Experiment was done to determine whether arginine or glycine was required to improve the adverse effect of a tyrosine excess diet. Chicks given the tyrosine excess diet demonstrated the retarded growth, depressed feed intake and decreased gain: feed ratio. These indices had a tendency to increase with the level of arginine•HCl (up to 2.0%) or glycine supplementation. The addition of 1.5 and 2.0% arginine•HCl to the tyrosine excess diet significantly (P<0.05) increased the feed intake and the addition of 4.0% glycine significantly (P<0.05) improved the gain: feed ratio. The decreased nitrogen retention rate, which was caused by feeding the tyrosine excess diet, was not improved by the supplementation of arginine or glycine. Chicks given the tyrosine excess diet significantly (P<0.01) increased the excretion of total creatinine. Supplemental arginine or glycine did not result in a substantial change in the increased excretion of total creatinine. The free tyrosine concentration in plasma was remarkably elevated by feeding excess tyrosine. When 2.0% arginine•HCl or 4.0% glycine was added to the tyrosine excess diet, plasma tyrosine concentration was slightly lower than that of chicks given the tyrosine excess diet. The results showed that the beneficial effect of supplemental arginine or glycine on the growth depression due to excess tyrosine could be attributed to the significant improvement of feed intake or gain: feed ratio.