Broiler chicken production using dietary crude protein reduction strategy and free amino acid supplementation

Very low self-sufficiency of soybean meal, which is the primary source of protein supplement used by European feed industry, caused great interest in EU to reduce the content of soybean meal in broiler chicken diets. The objective of this study was to evaluate the effect of reduced dietary crude protein (CP) and supplementation with 7 indispensable amino acids on broiler chicken performance and carcass composition. Two experiments (Exp.) were conducted, each with 2,640 fast growing broiler chickens. Grower diets were provided from d 10 to 31 in Exp. 1 and from d 10 to 28 in Exp. 2. In Exp. 1, broiler chickens were assigned to 4 treatments (22, 21, 20, and 18% CP diets supplemented with crystalline amino acids to achieve the same standardized ileal digestible (SID) Lys (10.9 g/kg), SID Met + Cys (8.07 g/kg), SID Thr (7.08 g/kg), SID Ile (7.63 g/kg), and SID Val (8.72 g/kg)) with 6 pens per treatment and 110 broiler chickens per pen. In Exp. 2, broiler chickens were assigned to 3 treatments (20, 19, and 18% CP diets supplemented with crystalline amino acids to have the same SID Lys, Met + Cys, Thr, Ile, and Val plus SID Arg (11.45 g/kg), and SID Trp (10.9 g/kg)) with 8 pens per treatment and 110 broiler chickens per pen. With decreasing CP from 20 to 18%, body weight decreased (P < 0.05). The greatest body weight was achieved at a CP concentration of 20% in both experiments (P < 0.05). In feed conversion ratio, breast meat yield, and an European efficiency factor, there were no differences between CP concentration 20 and 19% in Exp. 2. Based on the European efficiency factor, reducing dietary CP and adding crystalline amino acids seems to be a promising approach to achieve competitive broiler chicken meat production in Europe.