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Increasing Dietary Soybean Meal Level Improves Growth and Feed Conversion Efficiency in Healthy Pigs and Reduces GHG Emissions

Boyd, R., D. Rosero and A. Elsbernd

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%).