How high-concentrate feeding and the addition of clay minerals alter the rumen environment, microbiota, and gene expression in cows

Feeding of grain-rich diets to dairy cows induces a pH decrease in the rumen and initiates changes in both particle- (PaM) and epimural microbiome (EpM) with promotion of potential pathogens. Clay minerals have shown promising effects in binding pathogenic microorganisms and toxic compounds due to their high adsorption capacity. Therefore, this study evaluated the effects of repeated high-grain dietary challenges and the supplementation with a clay-mineral based mix (CM) on PaM, EpM, fermentation parameters and epithelial gene expression in cows. Samples for short chain fatty acid, as well as rumen-digesta samples and epithelial biopsies for microbial analysis and gene expression were collected via a cannula. SCFA were analyzed using gas chromatography. Microbial DNA was extracted and sequenced (MiSeq), targeting the V345 region of the 16S rRNA gene, and gene expression using RT-qPCR. Bioinformatic analysis was performed using QIIME. High concentrate feeding impacts population diversity and structure differently for PaM and EpM, and impacts microbial end products and gene expression. CM supplementation showed increasing effects on commensal microbiota and decreasing effects on possible pathogens.