Two experiments were conducted evaluating the effects of specialty soy protein products on nursery pig growth performance and fecal dry matter (DM). In Exp. 1, 360 barrows (DNA 200 × 400; initially 5.6 ± 0.02 kg) were used in a 37-d study to assess a refined soy protein concentrate (SPC) as a replacement for soybean meal (SBM) on a standardized ileal digestible (SID) Lys basis. Diets contained increasing SPC (0, 4.25, 8.5, 12.75, and 17%) replacing 0, 25, 50, 75, or 100% of SBM, and a positive control containing 8.5% enzymatically treated SBM (ESBM). Average daily gain (ADG) and gain-to-feed ratio (G:F) for the experimental period (d 0 to 23) increased (quadratic, P < 0.05) then decreased as SPC increased, with the greatest improvement observed when SPC replaced up to 50% of the SBM. Additionally, average daily feed intake (ADFI) increased (linear, P = 0.019) as SPC increased. Overall (d 0 to 37), increasing SPC increased (quadratic, P = 0.014) ADG and tended to increase (quadratic, P = 0.080) ADFI with the greatest response at 50% and 75% replacement of SBM, respectively. Gain-to-feed ratio tended to decrease (linear, P = 0.087) in pigs previously fed increasing SPC for the first 23 d. Fecal DM increased as SPC increased (linear, P = 0.035) on d 9, and pigs fed 50% SBM replacement (8.5% SPC) had greater (P = 0.011) fecal DM than those fed 8.5% ESBM. In Exp. 2, 1254 mixed-sex pigs (PIC 800 × [Fast LW × PIC L02]; initially 5.6 ± 0.10 kg) were used in a 28-d study to evaluate thermo-mechanically processed SBM (TM-SBM) at increasing levels replacing SBM on a SID Lys basis (0, 25, 50, 75, and 100% in phase 1 and 0, 12.5, 25, 37.5, and 50% in phase 2). For the experimental period (d 0 to 21), ADG and ADFI increased then decreased (quadratic, P ≤ 0.038) with the greatest improvement observed when TM-SBM replaced 25% to 50% of the SBM from d 0 to 7 and 12.5% to 25% from d 7 to 21 with an increase in G:F (quadratic, P = 0.036) observed with TM-SBM replacing 50% and 25% of the SBM from d 0 to 7 and d 7 to 21, respectively, but worsening thereafter. A treatment × day interaction was observed for fecal DM (quadratic, P = 0.024). On d 7, fecal DM increased when TM-SBM replaced 25% of the SBM (quadratic, P = 0.004), but decreased with 50% replacement before remaining constant, with no differences on d 21. Ultimately, replacing 25% to 50% of the digestible Lys provided by SBM in diets for 5- to 13-kg pigs with specialty soy products improved growth performance and fecal DM under the dietary formulation conditions used in these experiments.

Read the full paper here. Read more about Experiment 1 here and Experiment 2 here.

Smallfield, J., M. Tokach, J. Woodworth, J. DeRouchey, K. Gaffield, R. Goodband, J. Gebhardt, A. Warner, C. Hastad, L. Zou, S. May, W. Schweer and C. Pilcher. 2026. Effects of novel specialty soy protein products on growth performance and fecal dry matter of nursery pigs. Translational Animal Science, Volume 10, 2026. https://doi.org/10.1093/tas/txag066