Nitro- and nitrooxy-organic inhibitors of methanogenesis: revealing knowledge gaps and alternate ways in bovine rumen microbiome metabolism

In the rumen, methanogens consume H ₂ , generating methane and thermodynamically facilitating the production of short-chain fatty acids (SCFAs), ruminants’ main energy source. Yet in animal trials, inhibiting methanogenesis by 27%–90% with 3-nitrooxypropanol minimally perturbs ruminal SCFA levels, sparing disproportionately low amount of H ₂ . An Applied and Environmental Microbiology article (A. Castaneda, N. Indugu, K. Challa, K. Narayan, et al., Appl Environ Microbiol e01033-25, 2025, https://journals.asm.org/doi/10.1128/aem.01033-25 ) reports similar outcomes in an in vitro rumen experiment where ethyl-nitroacetate and ethyl-2-nitropropionate inhibited methanogenesis 100%. Hence, the rumen has fallback ways, perhaps evolved through exposures to plant metabolites. The nitroorganics offer an opportunity to determine the consequences of 100% inhibition of ruminal methanogenesis in live animals.