With the recent Renewable Fuel Standard Program developed by the Environmental Protection Agency, soybean oil is expected to be in record demand by the fuel energy industry. As a result, there will be the potential opportunity for increased usage of soybean meal (SBM) in swine diets. Therefore, the objective of this study was to evaluate the effect of different levels of SBM in late nursery diets on growth performance and fecal dry matter (DM). In Exp. 1,266 pigs (DNA 241 × 600; initially 10.1 ± 0.27 kg) were fed 1 of 4 dietary treatments which were corn-based with SBM levels of 25.0, 28.9, 32.5, or 36.2%. In Exp. 2,340 pigs (DNA 241 × 600; initially 13.5 ± 0.29 kg) were fed 1 of 5 dietary treatments which were corn-based with SBM levels of 25.0, 28.9, 32.5, 36.2, or 40.0%. Both experiments lasted 21 d with 14 replicate pens/treatment and 4 or 5 pigs/pen. At d 21 and 26 postweaning for Exp. 1 and 2, respectively, pens of pigs were randomly allotted to treatments in a randomized complete block design with BW as the blocking factor. Additions of SBM replaced feed-grade amino acids to form experimental diets, and all diets were formulated to be nearly isocaloric with SBM NE considered to be 100% of corn NE. Dietary additions of feed-grade AA were adjusted to meet or exceed NRC (2012) AA requirements in relation to Lys for Ile, Met, Cys, Thr, Trp, and Val. In Exp. 1, increasing SBM from 25.0 to 36.2% decreased ADG (linear, P=0.012), ADFI (linear, P < 0.001), and final BW (linear, P=0.021), with the greatest change occurring when SBM increased from 28.9 to 32.5%. No evidence for difference between treatments was observed for G:F (P=0.729). Fecal DM decreased (linear, P < 0.006) as SBM increased in the diet at d 7 but not on d 21. In Exp. 2, starting with a heavier initial BW, increasing SBM from 25.0 to 40.0% decreased ADFI (linear, P=0.017), with the greatest change occurring when SBM increased from 32.5 to 36.2%. However, no evidence for treatment differences (P≥0.198) was observed for ADG, final BW, or G:F. Fecal DM decreased (linear, P≤0.046) at d 7 and 21 as SBM increased in the diet.
In conclusion, feeding higher than 28.9% SBM for nursery pigs starting at 10 kg BW does compromise performance, but when pigs are closer to 13.5 kg BW, higher SBM diets did not affect ADG or G:F. Also, increasing the level of SBM reduced fecal DM more markedly a week after the transition to high SBM diets compared to 3 weeks after the start of treatment feeding.
