Effect of protein levels on broiler breeder hen diets on nitrogen and energy balance

Two experiments were carried out with the objective of testing the effects of diets with different crude protein levels on the balance of N and energy of broiler breeder hens at 36 and 46 weeks of age. The poultries were fed with diets containing 12.0; 13.5; 15.0; 16.5 and 18.0% crude protein and 2. 800 kcal of metabolizable energy/kg of diet, from 24 to 56 weeks of age. In both trials, linear effects of crude protein were observed on N intake and nitrogen excretion, but not on N retention. The effect of crude protein on gross energy excretion was quadratic at 36 weeks and linear at 46 weeks of age. There was a fourth degree effect on gross energy consumption and on a pparent metabolizable energy at 46 weeks of age. However, at 36 weeks of ag e there was no effect of crude protein on these variables. protein use was not efficient on diets containing crude protein levels above 12.0%.