Rumen Microbes Associated Potential to Establish Climate Resilience In Ruminants – A Review

Abstract Ruminants are stated to play a pivotal role of converting feed resources into nutritious outputs suitable for human consumption, which primarily is attributed to the diversified rumen microbiota they harbor. The rumen microbial niche is however not explored to its complete potential due to several limitations, the crucial one being the inability to culture more than 80% of the rumen microbes. Advances in next generation sequencing approaches have made promising inroads to bridge this gap. The adoption of techniques like 16S rRNA sequencing and whole genome shotgun metagenomics has now made it possible to assess the structural and functional dynamics of rumen microbiota. Nevertheless, there is a dearth of information pertaining to the impact of climate change on rumen microbe. This review was therefore an attempt to highlight the potential role of rumen microbiome during heat stress and also to emphasize on the significance of adopting rumen metagenomics to link climate change impact with altered productive potential in ruminants. Changes in ruminal microflora, like alterations in Firmicutes-Bacteroidetes ratio (highly correlated with milk fat yield), altered abundance of Fibrobacteres group (potentially heat generating microbes), Actinobacteria group (acetate producing microbes), Fusobacteria , Cyanobacteria and so on were observed in ruminants during heat stress. Furthermore, it was also possible to link these alterations with several functional and metabolic pathways, like energy production and conversion, defense mechanism, lipid transport and metabolism, coenzyme transport and metabolism, cell cycle control, cell division and a few more. Employing rumen metagenomics could also aid in understanding the differences in heat stress adaptive strategies between breeds. Therefore, intensifying the application of this methodology with heat stress in ruminants and extending it to assess the effectiveness of nutritional amelioration strategies could start a new journey towards heat stress mitigation in ruminants.