Response of broiler breeders to low-protein diets. 1. Adult breeder performance.

Four hundred female and 50 male commercial strain breeders were reared separately from 1 d to 18 wk of age, with all birds receiving the same diet. At 18 wk, all pullets were weighed and the extreme weights removed from the group. The remaining hens were then randomly sorted into four treatment groups each represented by four replicate groups. Treatment involved feeding different levels of CP (16, 14, 12, and 10%), supplemented with synthetic lysine and methionine in order to maintain constant lysine and TSAA levels, respectively. Diets were isoenergetic and all birds received the same quantity of feed daily. Dietary protein had no effect on egg production (P > .05). However, breeders fed 10% CP were lighter (P < .01) in weight than birds fed 16% CP. Eggs from birds fed 10 and 12% CP were consistently smaller (P < .01), and this resulted in reduced chick weight at hatching. Low-protein diets also resulted in less nitrogen excretion. These data suggest that it is possible to reduce the CP intake of broiler breeders while maintaining intake of critical amino acids without affecting performance.