156 Effects of Standardized Ileal Digestible Lysine Level on Growth Performance in 35 to 80 Kg DNA Finishing Pigs

Two studies were conducted to estimate the SID Lys requirement for growth and feed efficiency of 35-80-kg DNA finishing pigs. In Exp. 1, 608 pigs (600 × 241, DNA; initially 36.3±0.91kg) were used to estimate the SID Lys requirement from 35-55-kg. In Exp. 2, 700 pigs (DNA 600×241; initial BW of 53.2±0.86kg) were used to estimate the SID Lys requirement form 50-80-kg. Pens of pigs were blocked by BW and randomly allotted to 1 of 6 dietary treatments with 7-10 pigs/pen in a randomized complete block design with 12 replications per treatment. Diets were corn-soybean meal-based and SID Lys increased by increasing soybean meal and feed-grade amino acids while maintaining minimum ratios for other amino acids. Increasing SID Lys increased (linear, P < 0.05) ADG in both studies. From 50-80-kg, ADFI decreased, then increased (quadratic, P = 0.004) with increasing SID Lys. Feed efficiency improved, while Lys intake/d, and Lys intake/kg of gain increased (linear, P < 0.05, 35-55-kg; quadratic, P < 0.05, 50-80-kg) with increasing SID Lys. At current ingredient and pig prices, there were no statistical differences in income over feed cost (IOFC) from 35-55 kg. From 50-80-kg, increasing SID Lys increased (linear, P < 0.001) IOFC. Linear models resulted in the best fit for ADG, G:F and IOFC from 35-55-kg, with optimum performance at 1.20% SID Lys or greater. A quadratic polynomial model predicted a requirement of 0.97% SID Lys for optimum G:F from 50-80-kg. Meanwhile, a broken-line linear model predicted optimal IOFC at 0.76% SID Lys from 50-80-kg. In summary, these results suggest that the optimal SID Lys level for 35-55-kg DNA finishing pigs is at least 1.20%. The optimal SID Lys level for 50-80-kg DNA finishing pigs depends on the response criteria, with growth performance optimized at or above 0.97% SID Lys and IOFC maximized at 0.76% SID Lys.