Feeding high-fiber diets to finishing pigs can reduce performance and carcass yields. Therefore, our objective was to assess the impact of feeding high dietary fiber by using soybean hulls (SBH) and the strategy of withdrawing SBH in late finishing on growth and carcass performance. Two-hundred forty grower pigs (PIC 337×1050, 26.5 ± 3.03 kg BW) were blocked by sex, randomly allotted to pens (n = 15 pens/treatment) and assigned to one of four treatments which were fed in three dietary phases. Pigs were fed diets with either 0% SBH (CONTROL) or 22.5% SBH (SBH) throughout the study or withdrawn from SBH and placed on CONTROL diet 27 (SBH-27d) or 13 (SBH-13d) days before marketing. Dietary treatments were fed in meal form and formulated to equal grams of standardized ileal digestible lysine per megacalorie of metabolizable energy, while allowing energy to float. At the start and end of each phase, BW and pen feed disappearance were collected to calculate overall ADG, ADFI, and G:F. Pigs were marketed in three cuts to a target live BW of 135 kg. At a commercial harvesting facility, carcass weight, backfat depth, and loin depth were collected per pig, and carcass yield and fat-free lean were calculated. All data were analyzed in a randomized complete block design with block as a random effect, treatment as a fixed effect, and pen as the experimental unit. Pigs fed SBH throughout the study or had SBH withdrawn (SBH-13d and SBH-27d) had reduced overall G:F compared to CONTROL (0.35, 0.35, 0.36, 0.38, respectively, P < 0.001), with no differences on overall ADG or ADFI (P > 0.10). Final BW tended to be lowest in pigs fed SBH-13d, compared to CONTROL, with SBH-27d and SBH being intermediate (130.8, 134.1, 133.6, and 131.8 kg, respectively, P = 0.063). Carcass weight decreased (P < 0.001) by 8.3% and 4.7% for pigs fed SBH and SBH-13d, respectively, compared to pigs fed CONTROL, however pigs fed SBH-27d was similar (P > 0.10). Compared to the CONTROL, carcass yield was reduced in pigs fed SBH (75.0% vs 70.0%, respectively, P</em> < 0.001), with pigs fed SBH-27d and SBH-13d being intermediate (73.1% and 73.9%, respectively). Backfat (9.7, 14.0, 13.0, and 12.2 mm, respectively, P < 0.001) and loin (7.3, 7.8, 7.7, and 7.6 cm, respectively, P = 0.007) depth were also reduced on carcasses of pigs fed SBH compared to CONTROL, SBH-27d, and SBH-13d. Compared to the CONTROL, feeding pigs SBH, SBH-13d, and SBH-27d reduced carcass feed efficiency (0.26, 0.23, 0.23, and 0.22, respectively, P < 0.001). Altogether, feeding 22.5% SBH reduces live and carcass performance of grow-finish pigs. However, withdrawing SBH either 13 or 27 days before marketing can partially recover carcass yield and composition losses.

Miller, K., O. Mendoza and N. Gabler. 2025. Effects of high-fiber diets using soybean hulls and the withdrawal prior to market on growth performance and carcass composition of grow-finish pigs. 2025 American Society of Animal Science Midwest Section meeting, Abstract 31.

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