Abstract
Chicks fed a 20% casein-sucrose diet showed severe growth depression, but dietary supplementation with 0.7% arginine-HC1, 0.35% glycine and 0.35% DL-methionine improved the growth rate to almost that of chicks fed a practical diet. Chicks fed high protein diets containing 64% casein showed normal growth, irrespective of the supplementation with such amino acids. Plasma arginine concentration of growth-retarded chicks was significantly lower than that of normal chicks. Plasma threonine/arginine ratio was negatively correlated with the growth rate of the chicks, the ratio of normal chicks being 3-4 whereas that of growth-retarded chicks was about 24. No lysine-arginine antagonism occurred under high casein feeding.
