Impact of nutrition on the ruminal microbiome and epithelial tissue

Abstract Text: Ruminal microbiome composition and epithelial tissue function can influence the diet’s ability to address the nutrient requirements of cattle, but these associative effects are poorly characterized.  Experiments were conducted to determine the effect of two dietary strategies, subacute ruminal acidosis (SARA) and the inclusion level of condensed distillers solubles (CDS), on the ruminal microbiome and epithelial gene expression.  In both experiments, rumen samples were separated into solid and liquid fractions while epithelial papillae were excised from the rumen.  After using a feed restriction acidosis-induction model, relative abundance of Bacteroidetes was increased (P < 0.01) in the solid fraction of SARA cows compared with Non-SARA cows.  Quantitative PCR indicated greater Anaerovibrio lipolytica, Prevotella bryantii, and Succinimonas amylolytica (P < 0.03) after induction in the solid fraction of SARA cows, while Streptococcus bovis and Succinivibrio dextrinosolvens were greater (P = 0.02) in SARA cows pre- and post-induction.  The predicted functional profile of the solid fraction ruminal microbiome post-induction corresponded to known metabolites impacted by high-concentrate feeding.  Beta-diversity metrics indicated that in the liquid fraction the effect of day was greater than the effect from differences in ruminal pH response.  Effects of SARA on ruminal epithelium 24 hr post-induction were modest.  An increased expression of CLDN1 and CLDN4 (P = 0.01) was observed after feed restriction.  Results suggest that a more rapid adaption to a single bout of SARA occurred within the solid fraction microbiome.  As supplemental fat is often added to ruminant diets to increase the energy density of the ration, the effect of CDS inclusion at 0, 10, 19, and 27% in a coproduct based diet was determined.  The greatest effects were observed in the liquid fraction as species richness and alpha diversity decreased with greater CDS inclusion.  Linear increases of Firmicutes (P < 0.01) in the liquid fraction were driven by greater relative abundance of Ruminococcaceae (P < 0.01) with additional CDS.  Decreased Bifidobacteriaceae and Spirochaetaceae (linear; P < 0.02) in the liquid fraction were observed with greater CDS.  Relative abundance of Desulfovibrionaceae increased quadratically in the solid and liquid fraction with the highest levels at 19% CDS inclusion.  No effect of CDS was observed in ruminal epithelium expression of genes related to ketogenesis and transcription regulation. Overall, dietary composition and ruminal pH affected the ruminal microbiome community and epithelial gene expression and may influence nutrient utilization.  

Keywords: nutrition microbiome epithelium