245 Effects of Standardized Ileal Digestible Tryptophan to Lysine Ratio on Growth Performance of PIC Line 337-Sired Grow-Finish Pigs

Abstract

Abstract This study was conducted to estimate the SID Trp:Lys requirement for growth and feed efficiency of PIC 337 × 1050 pigs from approximately 46- to 73-kg. A total of 840 pigs [initial body weight (BW) = 45.9 ± 0.95 kg] were used in a 28-d growth performance study. Pens of pigs were blocked by BW and randomly allotted to dietary treatments with 22 to 27 pigs per pen and 7 replications per treatment in a randomized complete block design. Pens were provided 1 of 5 dietary treatments with increasing SID Trp:Lys ratios at 15, 17.5, 19, 21, and 23%. Two corn-soybean meal-based diets with 30% DDGS containing 15 and 23% Trp:Lys ratios were blended to achieve dietary targets for SID Trp:Lys. Average daily gain, ADFI, G:F, Trp Intake/kg of gain, and final BW increased (quadratic, P ≤ 0.008) with increasing Trp:Lys ratio, while Trp intake/d increased linearly (P < 0.001; Table). Additionally, Lys intake/d increased (quadratic, P = 0.009) while Lys intake/kg of gain decreased (quadratic, P = 0.008). A broken-line linear model predicted no further improvement to ADG beyond 19.5% SID Trp:Lys for 46- to 73-kg pigs. Meanwhile, a broken-line linear model suggested no further improvement to G:F beyond 19.3% SID Trp:Lys, while a similar fitting quadratic polynomial model suggested that maximum G:F was achieved at 21.3% SID Trp:Lys. In summary, these results suggest that the optimal SID Trp:Lys level for 46- to 73-kg pigs is 19.5% for ADG and 19.3 to 21.3% for feed efficiency.