Effects of novel specialty soy protein products on growth performance and fecal dry matter of nursery pigs

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, 1,254 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.