Addition of phytogenics and autolyzed yeast impact on the rumen epithelial microbes

The effectiveness of nutritional intervention strategies for the prevention of ruminal dysbiosis under modern feeding regimes remains unclear due to the complexity of the rumen ecosystem. The rumen epimural community, due to proximity, has the greatest opportunity to influence host gene expression with regards to barrier function, cell function and localized inflammation in high energy diets. The aim of this study was to determine the effect of two different feed additives on the rumen epimural community and host gene expression. Eight rumen cannulated Holstein cows were randomly assigned to one of three feeding groups: autolyzed yeast (AY), phytogenics (PHY) and control (CON). Cows were fed an intermittent SARA model which started with 100% forage diet (Baseline) followed by two 65% concentrate-diet induced SARA challenges (SARAI, SARAII), separated by one week of forage-only. Rumen papillae samples were collected via the cannula during the Baseline, SARAI and SARAII periods. Microbial DNA was extracted and sequenced targeting the 16S rRNA gene and host RNA was analyzed using RT-qPCR. Bioinformatics and statistics were performed using QIIME,R and SAS. Using the Shannon index for diversity, a tendency towards effect of feed additive treatment, and a tendency towards an interaction between treatment and feeding phase. Analysis of the taxonomic assignment at the genera level showed an increase in Pseudobutyrivibrio (P = 0.06), Selenomonas (P = 0.07) and SHD-231 (P = 0.01) in PHY treatment animals, whereas Succiniclasticum tended to decrease in both PHY and AY treated animals compared to the control. Linear discriminant analysis effect size testing was performed and based on treatment x feeding phase interaction, a number of biomarker genera were identified including the previously identified Succiniclasticum. Supplementation with AY correlated positively with CD14 and DRA expression but negatively correlated to CLDN1, MyD88, and MCT4 expression. Supplementation with PHY showed positive correlations to TLR4 and a negative correlation to CLDN4. Anaerovibrio showed the highest positive Pearson correlations to biogenic amines including putrescine (r = 0.67), cadaverine (r = 0.84), and tyramine (r = 0.83). These results show that the addition of feed additives to high grain production diets can have a positive influence on the epimural community stability and that changes in the epimural community are correlated with changes in host gene expression. Understanding the relationships between metabolic substrates such as biogenic amines and endotoxins can help to increase our understanding of the interactions between the diet, the microbiome and the host.