Effects of increasing soybean meal in late nursery, grower, and finishing pig diets.

Six experiments were conducted to determine the effects of increasing soybean meal (SBM) in late nursery and finishing pig diets on growth performance, fecal characteristics, and carcass traits. In Exp. 1, 266 pigs (initially 10.1 ± 0.17 kg) were randomly assigned to one of four corn-based diets with SBM levels of 25.0, 28.9, 32.5, or 36.2%. In Exp. 2, 340 pigs (initially 13.5 ± 0.18 kg) were randomly assigned to one of five corn-based diets with SBM levels of 25.0, 28.9, 32.5, 36.2, or 40.0%. In Exp. 1, increasing SBM from 25.0 to 36.2%, decreased (linear, P < 0.05) ADG, ADFI, and final BW, with no changes in G:F. In Exp. 2, increasing SBM from 25.0 to 40.0%, decreased ADFI (linear, P = 0.017). However, no effect of the SBM level was observed for ADG, final BW, or G:F. In Exp. 3, 615 pigs (initially 43.2 ± 0.68 kg) were randomly assigned to one of five corn-based diets with SBM levels of 19.1, 22.6, 26.3, 29.9, or 33.5% in a 28-d study. At the conclusion of the study, pigs were fed a common diet for 30 d, then re-allotted to one of five corn-based diets with SBM levels of 11.2, 14.2, 17.2, 20.2, or 23.2% (Exp. 4, initially 102.3 ± 1.55 kg). In Exp. 5, 1053 pigs (initially 39.1 ± 0.78 kg) were randomly assigned to one of five corn-based diets containing 20% of corn dry distillers grain with solubles (DDGS) with SBM levels of 18.2, 23.5, 28.9, or 34.3% in a 28-d study. At the conclusion of the study, pigs were fed a common diet for 30 d, then re-allotted (initially 102.2 ± 1.13 kg) to one of five corn-based diets containing 10% DDGS with SBM levels of 9.5, 13.5, 17.5, or 21.5%. For the grower phase, in Exp. 3, increasing SBM increased (linear, P = 0.05) ADG and G:F. However, when DDGS were included in the diet (Exp. 5), no differences were observed in growth performance. For late-finishing pigs (Exp. 4 and 6), no differences were observed for any growth performance or carcass criteria when increasing SBM in either corn or corn-DDGS-based diets. In conclusion, increasing SBM decreased growth performance in 10 kg nursery pigs but not in pigs initially 13.5 kg. In the grower phase, increasing SBM improved growth performance in corn-SBM-based diets, but not diets containing DDGS. During the late finishing phase, SBM level did not affect growth performance or carcass characteristics, regardless of diet formulation strategy.