The role of tryptophan in the nutrition of dogs on nicotinic acid-deficient diets.

It has now been definitely established that there exists an interchangeability of nicotinic acid and tryptophan in the nutrition of some animals on diets deficient in the vitamin and containing only suboptimal amounts of the amino acid (1-S). Because the dog has been employed as the experimental animal in the classical investigations on nicotinic acid deficiency, it seemed of interest to determine whether this same nicotinic acid-tryptophan relationship exists for this species. The results of these nutrition experiments, together with those obtained in the study of the urinary excretion of some nicotinic acid derivatives under these experimental conditions, are presented here.