Effect of dietary concentrations of energy, crude protein, lysine, and methionine on the performance of White Leghorn layers in the tropics

Three experiments were conducted using White Leghorn layers (Babcock) from 21 to 72 wk of age to evaluate the effect of dietary ME (2,350 and 2,600 kcal/kg) and CP (15, 16.5, and 18%; experiment 1), and supplementation of low-CP diets with graded concentrations (0.65, 0.70, 0.75, and 0.80%) of lysine (experiment 2) or methionine (0.305, 0.335, 0.355, and 0.395%; experiment 3) on layer performance. Each diet was fed ad libitum to 8 replicate groups housed in an open-sided poultry house (22.0 to 35.5 degrees C). Dietary concentrations of CP had no effect (P > 0.05) on egg production (EP), feed intake (FI), FE, egg weight, egg mass (EM), and BW, except the egg weight during the initial 3 periods, which was significantly lower in layers fed 15% CP. A higher (P < 0.05) rate of EP and higher FE and EM were observed in groups fed 2,600 kcal of ME compared with those fed 2,350 kcal of ME/kg. In experiment 2, EP, FI, and FE were not affected by dietary lysine concentrations, except for FI in period 7. Egg weight during the majority of periods and EM increased nonlinearly (P < 0.05 to 0.001) and linearly, respectively, with increasing dietary concentrations of lysine. Final BW increased linearly with increasing dietary lysine concentrations. In experiment 3, dietary methionine concentrations had no influence (P > 0.05) on EP. Feed intake decreased linearly and FE improved nonlinearly (P < 0.05) with increasing dietary concentrations of methionine. Egg weight increased nonlinearly with increasing methionine concentrations during periods 2, 8, and 9, and over the trial period. Dietary methionine concentrations did not influence EM (except during periods 2 and 8), shell defects, and BW. It was concluded, based on the data, that White Leghorn layers (21 to 72 wk) reared in open-sided houses in the tropics require approximately 0.70% lysine and 0.305% methionine in diets containing approximately 15% CP and 2,600 kcal of ME/kg while maintaining 16.5% CP during the initial phase of production for optimal egg size.