Effect of essential oils blend supplementation on correlation of metranscriptome of rumen microbes and rumen fermentation in murrah buffaloes

The aim of this study was to investigate the effect of supplementation of essential oil blend on rumen microbiome in a broad manner using metatranscriptomics and its correlation with fermentation in Murrah buffaloes. The essential oil blend (EOB) consisted of Cymbopogon citratus oil, Trachyspermum ammi oil, and Syzygium aromaticum oleoresin mixed in equal proportion and was supplemented to buffaloes at the rate of 0, 0.75 and 1.5 ml/100 kg of body weight in three groups, respectively. Correlation study was performed between fermentation attributes and rumen bacterial metatranscriptome to assess the interdependence and interaction of microbes on rumen fermentation and metabolites. There was a positive correlation of Methanobrevibacter with Butyrivibrio, Ruminococcus, Fibrobacter and Shewanella. Interestingly, archaea abundance and methane production were weakly correlated, whereas Methanobrevibacter had high positive correlation with methane production. Rumen enzymes involved in fibrous feed utilization like avicelase, β-glucosidase were highly positively correlated with Clostridium, Eubacterium, Roseburia, Ruminococcus, Butyrivibrio, Treponema, Alistipes, Fibrobacter, Paludibacter. In vitro feed fermentation also varied favorably with supplementation of EOB.