Use of the ideal protein concept in diets with different energy levels supplemented with phytase for broiler chickens of 1 to 21 days of age

An experiment was carried out to evaluate the performance and nutrients digestibility by broiler chickens in the period of 1 to 21 days of age. The experimental design was completely randomized, where T1 was the control treatment constituted by 21.1% of crude protein (CP), 3000 kcal of apparent metabolizable energy (AMEn)/kg, 0.46% of available phosphorus (AP) and 1.0% of calcium (Ca). T2 was the diet with 17.0% of CP and 3000 kcal of AMEn/kg, T3 the diet with 19.0% of CP and 2900 kcal of AMEn/kg, T4 the diet with 19.0% of CP and 3000 kcal of AMEn/kg, and T5 the diet with 19.0% of CP and 3100 kcal of AMEn/kg. Except for the control diet, the diets were formulated with 0.34% of AP, 0.80% of Ca and supplemented with phytase. The weight gains of the chickens were similar (P>0.05), independently of the experimental diets. However, the worst feed conversion was observed for the birds fed with 17.0% of CP. The birds which were fed diets with 19.0% of CP and 3000 or 3100 kcal of AMEn/kg showed performance similar to those fed with the control diet. The excretion of N and P reduced, on average, 16.5% and 22.0%, respectively, and there was increase in the P retention for the birds that were fed the experimental rations. The retention of Ca and N was smaller and similar, respectively, for the birds that consumed experimental rations. From these results, it is concluded that the diet with 19.0% of CP and 3000 kcal of AMEn/kg, supplemented with phytase, does not affect the 1-to-21-day-old broiler chickens and enables to decrease the environmental impact of the nutrients.