USO DO CONCEITO DE PROTEÍNA IDEAL EM RAÇÕES COM DIFERENTES NÍVEIS ENERGÉTICOS, SUPLEMENT ADAS COM FIT ASE PARA FRANGOS DE

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.