Abstract
The possible nitrogen sparing effects of supplementing amino acids to a protein free diet for chicks were investigated, using body weight loss and nitrogen balance as criteria. The amino acids were added, alone or in combination, in equimolar amounts of 20.1m mol/kg diet, equivalent to 0.3% methionine. Supplementation with single amino acids had no significant effect on body weight loss, but a combined supplement of methionine plus arginine plus threonine significantly reduced body weight loss. Methionine supplementation improved nitrogen balance significantly; the combined supplement of methionine plus arginine plus threonine had a similar but not significant effect. Other supplements that tended to reduce body weight loss also improved nitrogen balance, but not significantly. Total nitrogen measured in the gut contents of chicks given the protein-free diet or the diet supplemented with methionine and arginine gave no evidence of greater reutilization of endogenous nitrogen by the supplemented birds. Creatinine excretion by birds given the protein-free diet or diets supplemented with methionine, lysine or arginine did not account for differences in nitrogen balance.
