Nutritional effects on the growth and fatness of broilers

1. Broiler chickens given diets high in protein, or choice-fed on a high protein balancer, had much lower abdominal fat contents than those reported in many recent experiments. The values for males were 10.8 g/kg liveweight at 56 d at 2.43 kg liveweight in one experiment in Scotland and 16.0 g/kg liveweight at 42 d at 1.93 kg liveweight in another in South Africa. For females the values were 18.8 g/kg liveweight at 56 d at 2.15 kg liveweight in Scotland and 15.7 g/kg liveweight at 42 d at 1.60 kg in South Africa. 2. The content of abdominal fat was, in general, increased by reducing the protein content of the diet or by dilution of the food with oil or starch. It was, in general, reduced by diluting the food with dietary fibre which also reduced liveweight gain. 3. The results are consistent with the idea that chickens attempt to control their food intake so that they achieve a particular fatness. This level of fatness differs between the sexes and between degrees of maturity.