Evaluating the nutraceutical effects of increasing soybean meal in diets with or without distillers dried grains with solubles in growing and finishing pigs in commercial production

Abstract

Beyond amino acids, soybean meal (SBM) contains functional compounds such as isoflavones, saponins, and bioactive peptides that may influence immune and oxidative responses and shift energy allocation toward more productive processes. The experimental objective of was to assess the impact of increasing SBM, with or without distillers dried grains with solubles (DDGS), on biomarkers of immune and oxidative stress modulation and growth performance in grow-finish pigs under commercial conditions. Two experiments were conducted under commercial conditions: Exp. 1 (32 to 68 kg body weight (BW)), and Exp. 2 (78 kg BW to market). In each experiment, pigs were assigned to a 2 x 4 factorial arrangement with main effects of DDGS inclusion (0 or 30 percent in Exp. 1; 0 or 15 percent in Exp. 2) and increasing SBM level (17.5, 23.3, 29.1, or 34.9 percent or 3.9, 12.8, 21.8, or 30.6 percent with DDGS in Exp. 1; 6.5, 11.5, 16.4, or 21.3 percent or 0, 6.4, 12.8, or 19.2 percent with DDGS in Exp. 2), with 15 pens per treatment. Following Exp. 1, a washout period (68 to 84 kg BW; 14 days) occurred, and pigs were fed a common diet with 7.5 percent DDGS and medium SBM. On d-28 of each experiment, serum and plasma were collected from three pigs per pen for biomarker analysis. For digestibility, fecal and feed samples were collected from 8 pens per treatment on d-25 to 27 of each experiment. Pens were weighed every two weeks, feed disappearance was measured, and carcass characteristics were collected upon completion of Exp. 2. In Exp. 1, increasing SBM decreased ADFI (1.88 to 1.82 kg/d) and improved G:F (0.494 to 0.504) whereas 30 percent DDGS inclusion reduced ADFI and G:F compared to diets without DDGS (P[less than or equal to]0.05). In Exp. 2, 0 percent DDGS improved G:F compared to pigs fed 15 percent DDGS (P[less than or equal to]0.05), and increasing SBM improved G:F (0.385 to 0.392) but did not affect final BW (P[less than or equal to]0.05). Pigs fed diets without DDGS had increased HCW, carcass yield, and backfat depth (P[less than or equal to]0.05). Increasing SBM decreased carcass yield and backfat depth regardless of DDGS inclusion. Across both growth phases, increasing SBM elevated serum IL-8 (P[less than or equal to]0.05) and in Exp. 1, 30 percent DDGS inclusion tended to increase serum IL-8 (P=0.09). In Exp. 1, regardless of DDGS inclusion, increasing SBM elevated serum IL-10 (P=0.03), but tended to decrease circulating GM-CSF. Addition of 15 percent DDGS in Exp. 2 decreased serum IL-6 (P=0.06), and a trend toward an interaction between DDGS and SBM was noted in Exp. 2 for GM-CSF, IL-10, and TNF[alpha] (P<0.10).