The experiment was conducted to evaluate the effect of different energy levels and feeding programs on performance of broilers from 42 to 57 days of age. One thousand and six hundred 1-d male chicks (Cobb) were assigned to a completely randomized design with 2 x 4 factorial arrangement (two levels of energy: 3,200 and 3,600 kcal ME/kg and four different feeding programs: amino acid recomendations). From 1 to 41 days of age all birds were fed the same corn and soybean meal-based diet and, after, the experimental diets were fed. Weight gain, feed intake, feed:gain ratio at the end of each period, energy conversion and productive efficiency in the overall period were evaluated. The 3,600 kcal ME/kg level increased bird performance, but the partition of digestible amino acid requirements in both periods decreased performance. The performance from 50 to 57 days of age indicated that late slaughter must be anticipated one week, because after 49 days of age feed:gain ratio decreases.
digestible amino acids; metabolizable energy; regression equations
