Uso do conceito de proteína ideal em rações com diferentes níveis energéticos, suplementadas com fitase para frangos de corte de 1a 21 dias de idade

English. 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.

Portuguese. Avaliou-se o desempenho e a digestibilidade de nutrientes para frangos de corte de 1 a 21 dias de idade. O delineamento experimental foi inteiramente casualizado, sendo os tratamentos T1: ração controle com 21,1% de proteína bruta (PB), 3000 kcal de energia metabolizável (EMAn)/kg, 0,46% de fósforo disponível (Pd) e 1,0% de cálcio (Ca); T2: ração com 17,0% de PB e 3000 kcal de EMAn/kg; T3: ração com 19,0% de PB e 2900 kcal de EMAn/kg; T4: ração com 19,0% de PB e 3000 kcal de EMAn/kg; T5: ração com 19,0% de PB e 3100 kcal de EMAn/kg. Com exceção da ração controle, as rações foram formuladas com 0,34% de Pd, 0,80% de Ca e suplementadas com fitase. O ganho de peso das aves foi semelhante (P>0,05) em todos os tratamentos. Porém, observou-se pior conversão alimentar para as aves que receberam a ração com 17,0% de PB. As aves que receberam as rações com 19,0% de PB e 3000 ou 3100 kcal de EMAn/kg apresentaram desempenho semelhante àquelas que receberam a ração controle. A excreção de N e P reduziu, em média, 16,5 e 22,0%, respectivamente, e houve aumento na retenção de P para as aves que consumiram as rações experimentais. A retenção de Ca e N foi menor e semelhante, respectivamente, para as aves que consumiram as rações experimentais. Conclui-se que a ração com 19,0% de PB e 3000 kcal de EMAn/kg, suplementada com fitase, não afeta o desempenho de frangos de corte de 1 a 21 dias de idade e permite diminuir a excreção do N e do P.