206 Effects of Soybean Meal Concentration at a Fixed 12% Dietary CP on Growth and Carcass Performance of Finishing Pigs from 115 to 136 Kg.

Research has reported performance reduction when finishing pigs are fed corn-soybean meal diets formulated below 12% CP even when diets are fortified with all AA at or above minimum NRC (2012) requirements relative to Lys. A total of 280 pigs (DNA 600 × 241, initially 114.2 kg) were used in a 23-d trial to determine the effects of SBM concentration with CP fixed at 12% on finishing pig performance. Pens of 7 or 8 pigs (balanced number of pigs per treatment) were randomly assigned to 1 of 6 dietary treatments with 6 replications. Treatments consisted of 5 levels of SBM (10.6, 7.7, 4.9, 2.7, and 0%) with 12% CP and a negative control (NC) treatment with 4.0% SBM and 10% CP. All diets were formulated to 0.55% SID Lys with increasing levels of corn gluten meal used as SBM was decreased to maintain the 12% CP. Data was analyzed with PROC GLIMMIX procedure in SAS with pen as the experimental unit and initial BW as a blocking factor. For growth performance, decreasing SBM while maintaining 12% CP marginally decreased (linear, P=0.06) ADG (0.95, 0.94, 0.93, 0.90, and 0.90 kg/d), increased (linear, P=0.01) ADFI (3.36, 3.37, 3.43, 3.56, and 3.50 kg/d), worsened (linear, P<0.01) G:F (0.284, 0.278, 0.273, 0.253, and 0.257) and marginally worsened (linear, 0.07) final BW (136.2, 135.7, 135.7, 134.9, 134.9 kg). Feed intake was lowered (P<0.01) in pigs fed the diet with 12% CP and 10.6% SBM compared with pigs fed the NC diet (3.36 vs 3.60 kg), resulting in a marginal improvement (P=0.06) in G:F for pigs fed the 12% CP, 10.6% SBM diet (0.284 vs 0.267). For carcass characteristics, decreasing SBM decreased (linear, P=0.03) carcass ADG (0.73, 0.72, 0.71, 0.69, and 0.69 kg/d) and worsened (linear, P<0.01) carcass feed efficiency (0.218, 0.213, 0.209, 0.193, and 0.197). Pigs fed the diet with 12% CP and 10.6% SBM had improved (P=0.04) carcass G:F compared with pigs fed the NC diet (0.218 vs 0.204). Reducing the concentration of SBM worsened ADG, G:F, BW, carcass ADG, and carcass feed efficiency. Additionally, pigs fed the 12% CP and 10.6% SBM had improved G:F and carcass G:F compared with pigs fed the NC diet. These results suggest that reduced SBM concentration could be one of the reasons finishing pig performance is decreased when low CP diets are fed.