Modulation of the rumen microbiome of dairy cows by inclusion of a live yeast supplement in a total mixed ration

Abstract

Abstract High yielding dairy cattle are typically fed a total mixed ration (TMR) to meet their energy requirements. However, inadequate mixing can lead to feed selection and dietary imbalance, negatively affecting rumen metabolism and the microbiome. To investigate the effect of TMR mixing, four dairy cows were fed a partial mixed ration with dietary concentrates (4 kg/cow/day) added separately in even and uneven patterns of allocation (CA) with a Saccharomyces cerevisiae yeast supplement (YS) (1 g/cow/day). Rumen digesta samples were taken to measure microbial metabolism and microbiome using16S rRNA amplicon sequencing. No effect of CA on rumen metabolism was detected. YS inclusion tended to increase rumen pH (P= 0.088) reduce total VFA concentration (P= 0.033) and propionate concentration (P= 0.016). Clustering of the rumen microbiome was observed with YS supplementation, driven by a decrease in abundance of Gammaproteobacteria and Prevotellaceae OTUs respectively and an increase of a Christensenellaceae OTU. Pattern of concentrate allocation had no detectable effect on alpha diversity or Bray Curtis dissimilarity. However, reduction in relative abundance of a Prevotellaceae OTU biomarker was associated with uneven pattern of concentrate allocation. Pattern of concentrate allocation and YS supplementation did not adversely affect milk yield or composition.