Effects of Aspergillus oryzae fermentation extract on in vitro equine cecal fermentation

The objective of this study was to examine the effects of Aspergillus oryzae fermentation extract on the in vitro equine cecal fermentation of soluble starch, amino acids/peptides, coastal bermudagrass hay, and alfalfa hay. Cecal contents were obtained from a cecally fistulated Quarter Horse gelding fed coastal bermudagrass and grain (70:30) either unadapted or adapted to dietary A. oryzae supplementation (2 g/d). Mixed cecal microorganisms were incubated in anaerobic media for either 24 h (soluble starch, amino acids) or 48 h (bermudagrass hay, alfalfa hay). A. oryzae was added to the incubation bottles (n = 4) at concentrations of 0, .07, or .7 g/L. Fermentation of soluble starch in the presence of .7 g/L of A. oryzae resulted in increased concentrations of acetate, propionate, NH3, and L-lactate and decreased final pH. Addition of .7 g/L of A. oryzae to amino acid/peptide fermentations decreased final pH and increased concentrations of H2, acetate, propionate, butyrate, and total VFA. When alfalfa hay or bermudagrass hay was fermented with .7 g/L of A. oryzae, CH4, IVDMD, and digestion of NDF and ADF decreased. When adapted mixed cecal microorganisms were used, .7 g/L of A. oryzae did not inhibit methanogenesis or fiber digestion and L-lactate concentrations were not increased with soluble starch as the substrate. These results suggest that cecal microorganisms exposed to A. oryzae via the diet may adapt to the product. Incorporation of A. oryzae into in vitro incubations at concentrations similar to current recommended usage levels resulted in little change in final pH and fermentation products.