Some abstracts do not have video files because ASAS was denied recording rights.
471
The effect of binding feed emzymes to spores of bacillius Subtlis and bacillius Coagulans on in Vitro NDF digestibility in ruminal batch cultures
Immobilization of enzymes on Bacillus spores has been shown to enhance enzyme stability. Binding feed enzymes to spores may therefore protect them in the rumen environment and improve enzyme efficacy. The objective of this study was to determine whether a xylanase feed enzyme bound to the surfaces of Bacillus subtilis or Bacillus coagulans spores would improve in vitro ruminal NDF digestibility compared to free enzyme. Three separate in vitro ruminal batch cultures were performed on different days using the following treatments: B. subtilis spore-bound enzyme (BsubE; 1.0 × 109 B. subtilis spores + 0.1 mg xylanase enzyme protein); B. coagulans spore-bound enzyme (BcoaE; 1.0 × 109 B. coagulans spores + 0.1 mg xylanase enzyme protein); free enzyme (ENZY; 0.1 mg xylanase enzyme protein); and control (CON; water). The treatments were applied to alfalfa hay (2-mm particle size) 4 h before incubations. Rumen fluid was collected from two cannulated heifers and mixed with Menke’s buffer (3:1) under anaerobic conditions to make inoculant. Serum vials containing pre-treated alfalfa hay (0.5 g) were filled with 60 ml of inoculant and then incubated on a shaker (39°C) for 0, 3, 6, 12, 24 and 48 h. Triplicate vials were removed at each time point to measure gas production, methane emission, and alfalfa digestibility. Gas production (ml/g dry matter (DM)) at 48 h was not different between BsubE, BcoaE, or ENZY (P > 0.05); however, it was reduced in CON vials compared to the other treatments (P < 0.001). Methane emissions at 24 and 48 h (ml/g DM) were least for CON (25.2 and 29.8 ml/g, respectively), intermediate for the spore treatments (25.8 and 30.5 g/ml for BsubE; 25.9 and 30.7 g/ml for BcoaE), and greatest for ENZY (35.4 and 39.0 ml/g, respectively; P = 0.011). In vitro DM digestibility was not different at 24 h (P = 0.36), but at 48 h there was a difference between CON (78.9%) and BsubE, BcoaE and ENZY (average 80%; P = 0.018). There was a tendency for greater NDF digestibility at 48 h in the enzyme treatments, compared to CON (P = 0.075). These data showed that the feed enzyme enhanced digestion of alfalfa. However, there was no difference when the enzyme was applied in free-form or bound to spores. Protection of feed enzymes through absorption to Bacillus spores may be more effective when the enzymes are unstable in a ruminal environment.
Keywords: feed enzyme, rumen digestibility, spores