Effect of changes in dietary protein and oil levels on production parameters of female broiler chickens

Two experiments, as factorial arrangement of treatments in a complete randomized design, were conducted to evaluate weight gain (WG), feed conversion (FC), and carcass characteristics of female broilers fed diets varying in crude protein (CP) and metabolisable energy (ME) levels with graded oil supplementation. In experiment 1, the CP level was 190 and 220 g/kg in the starter diets and reduced by 25 g/kg for each grower diet with ME of 12.1 and 12.6 MJ /kg and oil level of 0 and 40 g/kg. In the second experiment, the level of CP was 190, 210, and 230 g/kg in the starter diets and reduced by 30g/kg in each corresponding grower diet with an oil level of 0, 20, and 40 g /kg. The 190 g/kg dietary CP reduced WG of birds at market age in both experiments but increased the FC value only in trial 2 (P < 0.05). In addition, it reduced protein and moisture contents but increased fat level in ready to cook (RTC) carcasses (P