The effect of dietary tryptophan and niacin levels on broiler breeder pullets.

A total of 1500 pullets and 300 cockerels were obtained at one-day of age and reared to six weeks on a commercial-type diet. At six weeks of age, birds were fed one of the following: Diets 1, 2 and 3 contained 0.150 percent tryptophan and no added niacin, 28 mg. added niacin and 250 mg. added niacin per kg. of diet, respectively. Diets 4, 5 and 6 contained 0.112 percent tryptophan and no added niacin, 28 mg. added niacin and 280 mg. added niacin per kg. of diet, respectively. All diets contained 2800 kcal. of metabolizable energy per kg. of diet and were fed for 21 weeks. The 0.112 percent tryptophan diets reduced body weight and percent body protein but increased percent body fat. Niacin levels had no effect on any of the pullet production parameters measured. However, at 21 weeks of age 280 mg. of added niacin in the 0.150 percent tryptophan diets restricted body weights of the males.