Rumen microbial community composition varies with diet and host, but a core microbiome is found across a wide geographical range

Ruminant livestock are important sources of human food and global greenhouse gas emissions.Feed degradation and methane formation by ruminants rely on metabolic interactions betweenrumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial communitycomposition was determined in 742 samples from 32 animal species and 35 countries, to estimateif this was influenced by diet, host species, or geography. Similar bacteria and archaea dominatedin nearly all samples, while protozoal communities were more variable. The dominant bacteriaare poorly characterised, but the methanogenic archaea are better known and highly conservedacross the world. This universality and limited diversity could make it possible to mitigate methaneemissions by developing strategies that target the few dominant methanogens. Differences inmicrobial community compositions were predominantly attributable to diet, with the host being lessinfluential. There were few strong co-occurrence patterns between microbes, suggesting that majormetabolic interactions are non-selective rather than specific