Novel feed enzyme delivery method: Binding exogenous feed enzymes to Bacillus spores to improve enzyme stability and total tract digestibility

  • Author / Creator
    Rosser, Christine L.
  • The effects of binding feed enzymes to Bacillus subtilis (strain RK28) spores on enzyme stability and digestion in cattle were studied in comparison to unbound enzymes. Optimal conditions for adsorbing six different enzymes (α-amylase, β-glucanase, feruloyl esterase, phytase, purified xylanase, and a commercial crude xylanase) to spores were first determined. Spore-bound enzymes were assessed using in vitro ruminal batch cultures for their impact on the degradability of feed substrates, including alfalfa: grass hay and a mixture of barley silage and concentrate (75:25 dry matter basis). Each enzyme was examined individually and in combination in either an unbound or spore-bound form. The batch culture studies were used to identify the most effective spore-bound enzyme for use in an in vivo cattle study. A commercial xylanase was selected to test the administration of spore-bound enzyme on digestibility of feed in the rumen, post-rumen, and total digestive tract of cattle fed an alfalfa: grass hay diet at 1.15% of body weight. The ability of spores to protect bound enzymes in temperatures representing feed processing, and in simulated gastric and intestinal environments, was also tested in vitro. The optimal spore-binding conditions varied according to enzyme being tested, as did the amount of enzyme that could be bound to spores and the retained activity of enzymes once bound to spores. Generally, the addition of enzymes to batch cultures improved degradability, and combinations of enzymes were marginally better than individual enzyme treatments. Spore-bound enzymes did not improve in vitro degradation or fermentation parameters compared with unbound enzyme. An exception to this was the spore-bound commercial xylanase, which reduced methane production and had greater xylanase activity during batch cultures, compared with unbound enzyme. When fed to cattle, there were no differences in in situ degradability variables for unbound compared with spore-bound commercial xylanase (P ≥ 0.315). Ruminal digestibility of organic matter decreased and intestinal digestibility increased, for spore-bound enzyme compared with unbound enzyme (P ≤ 0.028). In addition, there was a tendency for total tract digestibility of neutral and acid detergent fiber to be 4.9 and 4.0% greater for spore-bound enzyme compared with unbound enzyme (P ≤ 0.082). Incubating unbound commercial xylanase in intestinal fluid resulted in rapid degradation (>85%) within 3 h, whereas spore-bound enzyme activity decreased to a lesser extent (15%) and there was evidence of enzyme release by spores in the intestines (approximately 125% of 0 h activity after 6 h incubation). Throughout feed processing conditions, spore-bound enzymes also had increased stability compared with unbound enzymes. Thus, adsorption of feed enzymes to spores has potential to increase enzyme stability throughout feed processing and the gastrointestinal tract of ruminants resulting in increased total tract digestibility of neutral and acid detergent fiber.

  • Subjects / Keywords
  • Graduation date
    Fall 2018
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
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