The lack of response of broiler chickens to supplemental niacin when fed a corn-soybean meal diet from 3 to 7 weeks of age.

An experiment involving 1296 Cobb feather-sexed broiler chickens was conducted to determine their need for supplemental niacin from 3 to 7 wk of age when fed a corn-soybean meal diet. Birds were raised in litter floor pens to 3 wk of age and fed a diet that met or exceeded the 1984 National Research Council nutritional requirements. From 3 to 7 wk of age, birds were assigned to six dietary treatments consisting of 0, 3, 6, 12, 24, and 36 mg of supplemental niacin/kg of feed. Twelve replicate pens (six per sex) were fed each dietary treatment. The corn-soybean meal basal diet (unsupplemented with niacin) contained by analysis 21.3% crude protein, 23% tryptophan, and 22 mg of niacin/kg of feed. Birds were weighed at 3 and 7 wk of age on a per pen basis. The body weight gain, total feed intake, and feed conversion were determined for male and female chickens between 3 and 7 wk of age. There were no significant differences in body weight gain (P = .67), feed intake (P = .36), and feed conversion (P = .12) due to dietary treatments. Treatment by sex interaction was not significant for body-weight gain (P = .53), feed intake (P = .76), and feed conversion (P = .53). It was concluded that a corn-soybean meal diet containing 22 mg of niacin/kg (from corn and soybean meal) and .23% tryptophan was adequate for optimum growth and feed conversion of broiler chickens from 3 to 7 wk.