Fermentation of Soybean Meal Using a Novel Bacillus Subtilis Isolate to Improve Nutritive Value in Growing Pigs

Soybean meal (SBM) fed to pigs contains a variety of antinutritional factors that impair the digestion of protein and utilization of nutrients. In the current study, a commercial SBM was subjected to solid state fermentation (SBM: water, 1:1; inoculum, 1%; temperature, 22-25°C) using a novel Bacillus subtilis CP-9 expressing high level of cellulase, xylanase and protease activities. Protein profile of the SBM after 48 h fermentation showed degradation of high molecular weight proteins including antigenic proteins into small-size peptides on sodium dodecyl sulfate polyacrylamide gel electrophoresis. To examine if fermentation altered the nutritive value of SBM, eight barrows (40 ± 2 kg BW) fitted with terminal ileal T-cannula were used. Two semi-purified corn starch–based diets were formulated with unfermented (UF) and fermented (F) SBM as the sole source of AA (min 18% CP, as-fed basis). Pigs were allocated in a two-period cross over design (n = 8) and were fed at 2.8 × maintenance energy requirement. Each period was 9 d; 5 d for adaptation, d 6 and 7 for grab fecal collection and d 8 and 9 for 8 h continuous ileal digesta collection. The diet was considered fixed effect whereas pig and period were considered random effects in statistical analysis. Pigs fed F-SBM had higher (P<0.05) apparent ileal digestibility (AID) of CP (82.7 vs. 79.6%) and ash (46.3 vs. 43.0%) compared with pigs fed UF-SBM. There was no treatment effects (P> 0.10) on AID of NDF and ATTD of acid detergent fiber (ADF), neutral detergent fiber (NDF) and gross energy (GE). In conclusion, fermentation of SBM by a novel Bacillus subtilis CP-9 increased ileal utilization of crude protein and minerals suggesting improved nutritive value in pigs.