The effects of increased levels of niacin supplementation on growth rate and carcass composition of broiler chickens.

Four experiments were conducted to examine the response of broiler chickens to different levels of niacin. Practical-type diets, calculated to contain from 20.7 to 23.7 mg niacin per kg from intact ingredients, were fortified with a complete vitamin mixture which provided 33 mg supplemental niacin per kg of diet, in excess of the National Research Council (1977) suggested requirement of 27 mg per kg through 6 weeks of age. A niacinamide supplement was used to provide additional levels of 0, 33, or 66 mg per kg. Diets differed in content of added fat and energy levels in two of the experiments and in the presence or absence of animal protein sources in two others. The addition of niacinamide at 33 and 66 mg per kg to a diet already supplemented with 33 mg per kg from a complete vitamin premix, calculated to exceed the present NRC suggested requirement, resulted in improved body weight gains with sex differences noted in some experiments. Feed utilization was improved in some studies. There was no effect on the amount of abdominal fat or carcass dressing percentage. The results of these studies indicate that the modern rapidly growing broiler chick may require niacin levels greater than those generally recommended by the National Research Council (1977), which are based largely on studies where performance was considerably lower than obtained with the modern strains of broilers.