Standardized ileal digestible lysine requirement of male broilers at the age of 0–10 days

Two experiments were conducted to determine the standardized ileal digestible (SID) lysine requirement for 10-day-old male broilers. In experiment 1, 3 experimental diets including 2 diets composed of corn or soybean meal as the sole source of amino acids and an N-free diet were used to investigate standardized ileal digestibility of amino acids in corn and soybean meal for 11-day-old broilers. A total of 480 birds were allocated to the 3 treatments with a randomized complete block design, and each treatment included 8 cages per treatment and 20 birds per cage. In experiment 2, a total of 720 1-day-old birds were used for 10 days. The birds were allocated to 6 diets and 8 blocks with a randomized complete block design to estimate the SID lysine requirements. The 6 experimental diets were based on corn-soybean meal, and the concentrations of SID lysine in the diets increased equally from 9.8 g/kg to 14.8 g/kg with a consistent ratio of other indispensable amino acids. As the SID lysine increased, the average daily gain and gain:feed ratio increased linearly and quadratically (P < 0.05). The SID lysine requirements for average daily gain and gain:feed ratio were 13.27 g/kg and 12.89 g/kg for the one-slope broken-line, 15.33 g/kg and 13.99 g/kg for the quadratic broken-line, 14.56 g/kg and 13.24 g/kg for 95% of the upper asymptote of the quadratic model, and 14.18 g/kg and 13.56 g/kg for the first intercept between the plateau of the one-slope broken-line and quadratic models, respectively. In conclusion, the SID lysine requirements for 10-day-old broiler chicks fed corn-SBM-based diets ranged from 13.27 g/kg to 15.33 g/kg for average daily gain and from 12.89 g/kg to 13.99 g/kg for gain:feed ratio.