Frontiers in Microbiology (Dec 2016)

Synergism of cattle and bison inoculum on ruminal fermentation and select bacterial communities in an artificial rumen (Rusitec) fed barley straw

  • Daniela B Oss,
  • Gabriel O Ribeiro Jr.,
  • Marcos I Marcondes,
  • WenZhu Yang,
  • Karen A Beauchemin,
  • Robert John Forster,
  • Tim Mcallister

DOI
https://doi.org/10.3389/fmicb.2016.02032
Journal volume & issue
Vol. 7

Abstract

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This study evaluated the effect of increasing the proportion of bison relative to cattle inoculum on fermentation and microbial populations within an artificial rumen (Rusitec). The experiment was a completely randomized design with a factorial treatment structure (proportion cattle:bison inoculum; 0:100, 33:67, 67:33 and 100:0) replicated in two Rusitec apparatuses (n=8 fermenters). The experiment was 15 d with 8 d of adaptation and 7 d of sampling. Fermenters were fed a diet of 70:30 barley straw:concentrate (DM basis). True digestibility of DM was determined after 48 h of incubation from d 13-15, and daily ammonia (NH3) and volatile fatty acid (VFA) production were measured on d 9-12. Protozoa counts were determined at d 9, 11, 13 and 15 and particle-associated bacteria (PAB) from d 13-15. Select bacterial populations in the PAB were measured using RT-qPCR. Fermenter was considered the experimental unit and day of sampling as a repeated measure. Increasing the proportion of bison inoculum resulted in a quadratic effect (P0.05). Increasing bison inoculum linearly increased (P<0.05) concentrate aNDF disappearance, total and concentrate N disappearance as well as total daily VFA and acetate production. A positive quadratic response (P<0.05) was observed for daily NH3-N, propionate, butyrate, valerate, isovalerate and isobutyrate production, as well as the acetate:propionate ratio. Increasing the proportion of bison inoculum linearly increased (P<0.05) total protozoa numbers. No effects were observed on pH, total gas and methane production, microbial N synthesis, or copies of 16S rRNA associated with total bacteria, Selenomonas ruminantium or Prevotella bryantii. Increasing bison inoculum had a quadratic effect (P<0.05) on Fibrobacter succinogenes, and tended to linearly (P<0.10) increase Ruminococcus flavefaciens and decrease (P<0.05) Ruminococcus albus copy numbers. In conclusion, bison inoculum increased the degradation of feed protein and fibre. A mixture of cattle and bison rumen inoculum acted synergistically, increasing the DM and aNDF disappearance of barley straw.

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