Studies on the vitamin requirements of poultry. 8. Genetic differences in the requirements for niacin and riboflavin of meat-type and egg-type chicks

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.

SPARING ACTION BETWEEN METHIONINE, CHOLINE AND VITAMIN B-12 IN CHICKS AND HENS

Two experiments were conducted with White Leghorn strain-cross chicks and two with the same strain of hens in an attempt to determine whether the methionine supplement frequently added to practical corn, soybean meal-type diets could be partially or completely replaced by choline and/or vitamin B12. Methionine, choline and vitamin B12were studied using a factorial design. Significant growth and feed efficiency responses with chicks were obtained only with methionine, suggesting that the diet was adequate in methyl groups as well as in essential choline and vitamin B12. Neither choline nor vitamin B12spared the chicks’ needs for methionine. Based on the statistical analysis, the laying diets were adequate in methyl groups for egg production and feed efficiency, since choline and vitamin B12were not effective in sparing the requirement of methionine for these functions. On the other hand, in one experiment choline supplementation resulted in slight improvement in several parameters of economic importance, suggesting a need for additional methyl groups in the diet employed. Vitamin B12was found to be capable of sparing the need for methionine for egg size, under certain circumstances.