Document Type

Thesis - Open Access

Award Date

2025

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Eric Weaver

Abstract

The increasing demand for soybean production in the Midwest, driven by new soybean crushing plants, may reduce the cost of soybean meal (SBM), making it a more accessible and economically viable feed ingredient in swine diets. Replacing dried distillers grains with solubles (DDGS) with SBM and soy hulls at different inclusion rates may influence growth performance, carcass traits, nutrient digestibility, manure nutrient output, pelleting energy use, and economic returns in wean-to-finish pigs. Two experiments were conducted to evaluate these effects. In the first, 566 pigs (PIC × Terminal Duroc, 8.45 and 7.25 kg, 6 weeks of age) were housed in two environmentally controlled rooms with partially slatted floors and assigned to 40 pens (14 pigs/pen). Treatments consisted of diets containing either high (40%) or low (20%) DDGS, or SBM and soy hulls replacing the respective DDGS levels. In the second study, 275 pigs (PIC × Terminal Duroc, 12.8 kg, 7 weeks of age) were housed in a fully slatted facility and assigned to 46 pens (6 pigs/pen) to evaluate high (50%) vs. low (20%) SBM inclusion. All diets were formulated to meet or exceed NRC (2012) requirements with consistent standardized ileal digestibility (SID) lysine and net energy (NE) across treatments. NE values were set at 2,502 kcal/kg for SBM, 2,343 kcal/kg for DDGS, and 2,672 kcal/kg for corn. Data were analyzed as randomized complete block designs with pen as the experimental unit, treatment as the fixed effect, and block/room as the random effect. Across both studies, average daily gain (ADG) was not significantly affected by dietary treatment (P > 0.10). In Study 1, pigs fed SBM and soy hulls diets had improved feed efficiency (6% improvement in gain-to-feed) and lower feed intake compared to DDGS diets (P < 0.05). Digestibility effects varied by phase: during the grower period, crude protein (CP) digestibility was greater in low SBM vs. low DDGS diets (P < 0.05), while in the finisher phase, pigs fed low DDGS had greater DM, OM, GE, and ash digestibility (P < 0.05). No significant differences were observed in carcass traits (HCW, backfat, loin depth, lean %) or manure nutrient concentrations (CP, N, K, P; P > 0.10). In Study 2, feed intake, feed efficiency, and growth performance were unaffected by SBM inclusion level (P > 0.10). Economic analysis indicated that SBM-based diets are generally not competitive with DDGS diets for overall wean-to-finish production unless SBM costs decrease significantly relative to DDGS. However, high SBM diets showed profitability advantages in early growth phases (particularly 13–30 kg BW), and low SBM diets outperformed DDGS during targeted mid-growth periods. In conclusion, strategic use of SBM and soy hulls in place of DDGS can improve feed efficiency without compromising carcass traits, nutrient digestibility, or manure nutrient output. While not broadly economical under current market conditions, SBM inclusion may provide targeted profitability advantages during specific growth phases or in a shifting soybean market.

Publisher

South Dakota State University

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Rights Statement

In Copyright