Metabolizable energy levels for slow growth male broilers raised in semi confined system

Three trials were conducted to evaluate the metabolizable energy (ME) levels and the energy to protein ratio for slow growth male broilers raised in semi confined system in the starter (1 to 21), grower (22 to 49) and final phase (50 to 70 days old). In each experiment, 400 males ISA Label line in the raising phase were allotted to experimental installation constituted by 20 lots with cover area of 3.13 m(2) for feeding and gathering of the birds and a pasture area of 72.87m(2). A completely randomized experimental design was used, with five levels of ME and four replications of 20 birds per experimental unit. The levels of metabolizable energy fed in the ration in the different phases varied in the starter from 2,600 to 3,200 kcal/kg, in the grower from 2,700 to 3,300 kcal/kg and in the final from 2,800 to 3,400 kcal/kg. The crude protein and other nutrients were maintained at the same level in all diets according to the NRC (1994) recommendations, for each phase. The energy to protein ratio and the metabolizable energy that provide the best performance and carcass traits of male broilers ISA Label raised in semi confined system in each phase were: 128 and 2,750, 147 and 2850 and 172 and 3,100 kcal ME/kg of diet in starter, grower and final phases, respectively.