Dietary Energy, Digestible Lysine and Available Phosphorus Levels Influence Growth Performance and Carcass Traits of Broilers

Energy (E) and amino acids (AA) are two of the most expensive components in broiler diets. There is no general consensus regarding the interaction of E and AA on broiler performance and this requires further investigation. Phosphorus (P) is the third most expensive diet component after E and AA (Woyengo and Nyachoti, 2011). Phosphorus plays a vital role in E and AA metabolism, and protein synthesis while P requirement has not been established with certainty. It was hypothesized that the requirements of digestible lysine (dLys, based on the ideal ratio as suggested by Baker and Han, 1994), AMEn and available P (avP) for broilers are not in the same proportion and these nutrients may interact with each other to affect broiler performance. To test this hypothesis, an experiment was conducted using a 3-factor-3-level Box-Behnken design that included dLys (9.5, 10.5, 11.5 g/kg), AMEn (12.77, 13.19, 13.61 MJ/kg) and avP (3.0, 4.0, 5.0 g/kg) generating a total of 15 treatments with 5 replicates of 12 birds. A total of 1050 d-old Ross 308 male broiler chicks were fed a common starter diet (dLys 12.0 g/kg, AMEn 12.77 MJ/kg, avP 4.5 g/kg) up to d 14 and allocated to treatment diets from d 14-34. Response surface was fitted by first, second or third degree polynomial regressions in JMP statistical software v. 12.0.1.