Ruminants produce edible products and contribute to food security. They house a complex rumen microbial community that enables the host to digest their plant feed through microbial-mediated fermentation. However, the rumen microbiome is also responsible for the production of one of the most potent greenhouse gases, methane, and contributes about 18% of its total anthropogenic emissions. Conventional methods to lower methane production by ruminants have proved successful, but to a limited and often temporary extent. An increased understanding of the host–microbiome interactions has led to the development of new mitigation strategies. In this Review we describe the composition, ecology and metabolism of the rumen microbiome, and the impact on host physiology and the environment. We also discuss the most pertinent methane mitigation strategies that emerged to balance food security and environmental impacts.
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The authors acknowledge the collaborative nature of the work on the rumen microbiome by thanking the global scientific community involved in rumen microbiome research and the deciphering of its mysteries. The authors also thank E. Jami (Agricultural Research Organization, Volcani Center, Israel) and E. A. Bayer (The Weizmann Institute of Science, Israel) for critical reading of the manuscript. Research in the authors’ laboratory was supported by grants from the European Research Council (No. 640384) to I.M. and from the Israel Science Foundation (ISF No. 1947/19) to I.M. and S.M.
The authors declare no competing interests.
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Food and Agriculture Organization of the United Nations (FAOSTAT) enteric fermentation: http://www.fao.org/faostat/en/#data/GE
- Core microbiome
A group of microorganisms commonly found within the microbiome across multiple hosts.
- Food webs
The interconnections among different microbial food chains.
- Electron sinks
In this context, microorganisms within a microbial community that accept electrons at the final step of the electron flow.
Methanogens that use H2 to reduce CO2 to methane.
Methanogens that use a methylated compound as the input metabolite to produce methane.
- Acetoclastic methanogens
Methanogens that use acetate to produce methane.
- Alternative stable community states
Assemblages of functional groups that are locked and stabilized by metabolic feedback and result in distinct composition, function and, thus, outcome.
- Functional microbial groups
Groups of organisms that share similar functionality within the ecosystem.
- Horizontal gene transfer
(HGT). The lateral mobilization of genetic material between distinct microorganisms.
- Rumen plasmidome
The collective plasmid population in the rumen.
The collection of antibiotic resistance genes in a given environment.
The microbial transformation of unsaturated fatty acid to saturated fatty acid.
- Residual feed intake
A parameter that describes feed efficiency, measuring the difference between the actual feed intake and the predicted intake, based on an animal’s body weight, weight gain and milk composition, and is a proxy for the animal’s ability to extract energy from its feed.
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Mizrahi, I., Wallace, R.J. & Moraïs, S. The rumen microbiome: balancing food security and environmental impacts. Nat Rev Microbiol (2021). https://doi.org/10.1038/s41579-021-00543-6