A total of 360 barrows (200 × 400, DNA; initially 5.6 ± 0.02 kg) were used in a 37-d study to evaluate the effects of increasing levels of soy protein concentrate on growth performance and fecal dry matter. At weaning, pens of pigs were randomly allotted to one of six dietary treatments in a generalized randomized block design with body weight as a blocking factor. There were five pigs per pen and 12 pens per treatment. Experimental diets were fed in two phases from d 0 to 9 (phase 1) and d 9 to 23 (phase 2) followed by a common phase 3 diet from d 23 to 37. Treatments were corn-soybean meal-based and consisted of increasing soy protein concentrate (SPC; PurePro Soy, Bunge; Chesterfield, MO) at 0, 4.25, 8.5, 12.75, and 17% replacing soybean meal (SBM) in the diet. The diet containing 17% SPC replaced 100% of the SBM. A sixth diet served as a positive control containing 8.5% enzymatically treated SBM (HP 300, Hamlet Protein; Findlay, OH) partially replacing SBM in the diet. All diets were formulated to the same standardized ileal digestible lysine (SID Lys) level and were similar in energy content with SBM net energy (NE) considered to be 100% of corn NE. Dietary additions of feed-grade amino acids (AA) were adjusted to meet or exceed AA requirements in relation to Lys for Ile, Met and Cys, Thr, Trp, and Val. On d 9 and 23, fecal samples were collected from the same three randomly selected pigs in each pen to determine fecal dry matter (DM). During the experimental period (d 0 to 23), ADG and G:F increased (quadratic, P < 0.05) as SPC increased with the greatest improvement in ADG and G:F when SPC increased from 0 to 8.5%. Pigs fed 8.5% SPC or 8.5% HP 300 had similar performance (P > 0.10). Additionally, ADFI increased (linear, P = 0.019) as SPC increased. Overall (d 0 to 37), increasing SPC (d 0 to 23) increased ADG (quadratic, P = 0.014) and ADFI (quadratic, P = 0.080) with the greatest response observed at 8.5% SPC. However, overall G:F tended to decrease (linear, P = 0.087) in pigs fed increasing SPC for the first 23 d after weaning. Fecal DM, increased as SPC increased (linear, P = 0.035) on d 9, and pigs fed 8.5% SPC had greater (P = 0.011) fecal DM than those fed 8.5% HP 300. However, no differences in fecal DM were observed on d 23. In summary, partial replacement of SBM with 8.5% SPC improved nursery pig growth performance compared to other inclusion levels and resulted in higher fecal DM compared to HP 300.

Smallfield, J., M. Tokach, J. Woodworth, R. Goodband, J. DeRouchey, K. Gaffield, J. Gebhardt and L. Zou. 2025. Evaluating increasing levels of soy protein concentrate on growth performance and fecal dry matter of nursery pigs. 2025 American Society of Animal Science Midwest Section meeting, Abstract 20.