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Effect of Exogenous Enzyme Supplementation and Fermentation of Oilseed By-products on in vitro Digestibility and Production of Short Chain Fatty Acid

Jang, J., A. Javaid, P. Urriola and G. Shurson

An experiment was conducted to investigate the effect of exogenous enzyme supplementation and solid-state fermentation (SSF) with a mixed bacterial culture on in vitro dry matter digestibility (IVDMD) and short chain fatty acid (SCFA) production of soybean meal (SBM) or rapeseed meal (RSM). A 2 × 2 factorial design was used and included the factors of 1) exogenous enzyme cocktail (supplemented and non-supplemented), 2) microbial fermentation (fermented and non-fermented) applied to SBM or RSM in vitro. The exogenous enzyme cocktail consisted of non-starch polysaccharide (NSP) degrading enzymes (NSP-EZ) with phytase (10,000 FTU/kg), and the SSF were carried out using Bacillus subtilis. The fermented feed ingredients were collected after 48 h incubation at 37oC. Samples were hydrolyzed in two steps using pepsin and pancreatin to calculate IVDMD. Subsequently, the hydrolyzed residues were filtered, dried, and pooled for incubation in a buffered mineral solution with fresh swine feces. Gas production kinetics during fermentation was measured for 72 h and analyzed by fitting data to an exponential model. The fermentation residues were filtered, and the supernatant was analyzed for concentration of SCFA. The IVDMD from simulated gastric and small intestinal hydrolysis was greater (P < 0.01) for SSF in both SBM and RSM. During fermentation, the hydrolysis residue from SBM treated with SSF required less time to reach half asymptote, had greater maximal gas production, and greater fractional degradation (P < 0.01, respectively) compared with non-fermented SBM. The IVDMD from simulated total tract digestion was greater (P < 0.01) for SSF in RSM compared with SBM, while SBM had greater IVDMD for both SSF and NSP-EZ (P < 0.01). Production of butyric acid was greater for SSF (P < 0.01) compared with non-SSF in both SBM and RSM.

These results suggest that SSF can improve IVDMD and produce greater amounts of butyric acid compared with NSP-EZ supplementation in SBM and RSM.