The objective of this study was to determine the growth response to increasing soybean meal (SBM) dose (low, medium, high) compared to a high-energy, low SBM reference diet (HE L-SBM). A total of 2283 PIC terminal pigs (initial BW=44.25+1.14 kg) were used in a fixed time assay (ca. 133.63+1.23 kg). Pigs were placed in 96 mixed-sex pens (23-25 pigs/pen; 0.75 m2/pig), blocked by pen BW and allotted to 4 diets (HE L-SBM, L-SBM, M-SBM, H-SBM), which were fed in 4 phases beginning at 40.8, 59.0, 86.2, 104.4 kg BW. Dietary level of SBM corresponded to 19.0, 19.0, 24.5, and 30.0% respectively (phase 1); 14.0, 14.0, 18.0, and 22.0% (phase 2); 9.5, 9.5, 13.0, and 16.5% (phase 3) and 7.5, 7.5, 10.5, and 13.0% (phase 4). The HE L-SBM diet contained 20% DDGS, SBM equal to L-SBM diet, amino acids, 3.0% CWG. Diets exceeded NRC (2012) recommendations for nutrients, were iso-nutrient and SID Lysine:NE ratio was kept constant within dietary phase. The HE L-SBM diet had ca. 52 kcal NE/kg advantage to L, M, H-SBM diets (isocaloric). Early growth (phase 1) tended to be greatest for H-SBM (0.917, 0.919, 0.938 kg/d, P=0.118); each exceeding the summer reference diet (HE L-SBM 0.883, P< 0.001). In phase 2, pigs fed SBM diets grew similarly at each level (0.902, 0.920, 0.917 kg/d); HE L-SBM was inferior (0.883, P< 0.010). All diets performed similar for growth in phases 3, 4 (0.932, 0.736 kg/d). Carcass weight was the greatest for M-SBM, L-SBM diets (98.5, 98.6 kg) compared to HE L-SBM (97.1, P< 0.072). Whole-body G:F was greater for H-SBM vs L-SBM, M-SBM (0.354, 0.346, 0.339; P< 0.116, P< 0.005) and equal to HE L-SBM (0.355).
Thus, early growth benefitted from H-SBM; DDGS reduced gain despite fat addition. Caloric efficiency favored H-SBM (9.466 Mcal/kg gain) over HE L-SBM (10.098), as did predicted GHG emission (< 4.6%).