Effects of different mixtures of fibrolytic enzymes on digestion and fermentation of bahiagrass hay

This study was designed to determine the best combination of ferulic acid esterase (FAE), cellulose (CEL), and xylanase (XYL) for hydrolyzing mature bahiagrass in the absence of rumen fluid, and to evaluate effects of the best multienzyme cocktails on digestibility and fermentation of bahiagrass in the presence of rumen fluid. In Experiment 1, 42 enzyme mixtures of pure CEL, XYL, and FAE were dissolved in a citrate phosphate buffer (pH 6.0) and added to 0.5 g of a 12-week regrowth of bahiagrass (Paspalum notatum) hay. In each mixture, each enzyme was applied at 0, 0.5, 1, or 2 g/100 g of dry matter (DM) except that FAE was not applied at 2 g/100 g DM. Dry matter (DM) disappearance was measured after the solutions were incubated at 39 °C for 24 h. Each enzyme was applied in triplicate and the experiment was repeated thrice. The highest DM disappearance was with enzyme cocktails containing 2, 2, and 0 (2–2–0) or 2, 2, and 1 (2–2–1) g of XYL, CEL, and FAE, respectively/100 g of forage DM. In Experiment 2, the hay was treated with nothing (Control), a commercial enzyme preparation (Depol 740, D740L) containing all three enzymes, or the 2–2–0 and 2–2–1 enzyme cocktails from Experiment 1. The enzyme mixtures were dissolved in 1 ml of citrate–phosphate buffer (pH 6.0) and sprayed on 0.5 g of bahiagrass hay in triplicate in each of two runs. Samples were fermented in buffered-rumen fluid using a wireless automated gas production system for either 24 or 96 h in duplicate runs, and residues were analyzed for DM and volatile fatty acid concentrations. The kinetics of 96 h fermentation were determined by fitting a non-linear model to the data. For the 24 h fermentations, enzyme application did not increase DM or NDF digestibility but all enzyme mixtures decreased acetate concentration (P<0.001) and increased (P<0.04) propionate and butyrate concentrations. Consequently, all enzyme mixtures decreased (P<0.001) the acetate to propionate ratio. For the 96 h fermentations, all enzyme mixtures decreased the lag phase (P<0.05) but did not impact DM or NDF digestibility, gas pool size or fermentation rate. This study identified certain mixtures of XYL, CEL, and FAE that increased 24-h DM disappearance of bahiagrass in the absence of rumen fluid. Application of these multienzyme cocktails reduced the lag phase and improved efficiency of fermentation of mature bermudagrass in rumen fluid but did not improve extent of DM digestion.