Paul Smith, Sinéad Waters and David Kenny of Teagasc Grange and Alan Kelly (UCD) report on the rumen microbiome and low methane- emitting beef cattle.
Enteric methane originating as a by-product of the microbial fermentation of feed in the rumen accounts for nearly 60% of Irish agricultural- related greenhouse gas (GHG) emissions. To achieve the 25% reduction in total agricultural emissions by 2030, a minimum 10% reduction in ruminant-derived methane emissions has been set. Recent evidence from research led by Teagasc, in collaboration with the Irish Cattle Breeding Federation (ICBF) and UCD, has shown that some cattle can emit up to 30% less methane, for the same level of performance, when ranked on the basis of the residual methane emissions (RME) index. As the rumen is the sole source of enteric methane emissions, researchers in Teagasc and UCD, through the RumenPredict and EU-funded MASTER project, aimed to establish the contribution of the rumen microbial community to inter-animal divergence in methane output. To do so, rumen fluid digesta samples were obtained from nearly 300 intensively finished beef cattle that had previously undergone detailed measurements of enteric emissions and been ranked for RME, and samples were sent for high-throughput next-generation
There were no major differences in the composition of the rumen microbial community between high and low methane- emitting animals, but a small cohort of rumen microbes accounted for some 20% of the variation in emissions. Among the key microbes identified, low-RME (low methane emitting) animals had an increased amount of bacteria associated with production of lactic acid and its subsequent conversion into the volatile fatty acid (VFA) propionate. No evidence of an increased incidence of ruminal acidosis was observed, with similar ruminal pH reported between high and low methane-producing cohorts. A shift towards a less methanogenically potent community of rumen methanogens was observed in low-RME animals. Results from this study, which were recently published in Frontiers in Microbiology, have identified some of the key rumen microbes associated with a low methane emissions phenotype. Working with colleagues in New Zealand, further research has been initiated to assess the suitability of utilising the rumen microbial profile as a proxy for identifying low methane-emitting animals and the potential, through early life intervention, to inoculate the rumen of young animals with some of the key microbes associated with a reduced methane output.
This article was first published in the Teagasc Beef Newsletter - March 2023
