Improvement of in vitro ileal dry matter digestibility by non-starch polysaccharide degrading enzymes and phytase is associated with decreased hindgut fermentation

Efficacy of 11 non-starch polysaccharide (NSP) degrading enzymes (NSP-EZ) was evaluated when added to wheat middlings (WM) or corn distillers dried grains with solubles (cDDGS) using in vitro enzymatic digestion followed by fecal fermentation. For the in vitro enzymatic digestion, NSP-EZ and phytase (10,000 FTU/g) solution were added to WM and cDDGS samples at 20 times of the suppliers' recommended doses. After enzymatic digestion, the hydrolyzed residues were filtered, dried, and pooled for subsequent inocubation in a buffered mineral solution with feces from pigs fed corn and soybean meal based diets. Gas production during fermentation was measured for 72 h, and its kinetics were analyzed by fitting data to an exponential model. The fermentation residues were filtered, and the supernatant was analyzed for concentration of VFA. Addition of NSP-EZ increased (P >  0.05) digestibility of dry matter (3.2%) and energy (4.2%) and solubilization of glucose and protein in WM, but not in cDDGS. During fermentation, the hydrolysis residue from WM treated with NSP-EZ had less (P <  0.05) maximal gas production, greater time to reach half asymptote, and less concentration of SCFA compared with WM control. Fermentation of WM resulted in greater (P <  0.05) disappearance of dry matter (IVFDM) than WM with added NSP-EZ. but there were no differences among cDDGS with or without NSP-EZ. The NSP-EZ containing xylanase activity had a lower (P < 0.01) fractional rates of degradation at T/2 (μT/2) and tended (P = 0.073) to have a lower IVFDM in WM compared with those without xylanase activity. In summary, exogenous NSP-EZ increase in vitro ileal digestibility of dry matter and GE in WM, but decreased fermentation of WM enzymatic residues. These results imply that fiber structure of WM may be modified by NSP-EZ, which may result in partial degradation during small intestine hydrolysis, but fiber in hydrolysis residues appears to be resistant to subsequent microbial fermentation.