Summary
This systematic review synthesised evidence on feed additives designed to mitigate enteric methane emissions from cattle, a major contributor to livestock greenhouse gas output. The authors evaluated additives operating through two mechanisms: direct inhibition of methanogenesis (3-nitroxypropanol, nitrates, macroalgae) and rumen environment modification (lipids, plant secondary compounds, essential oils). Efficacy varied considerably across additive types, with medium-chain and polyunsaturated fatty acids showing substantial promise but inconsistent results, whilst secondary plant compounds and essential oils demonstrated highly variable effects ranging from significant reductions to modest increases in emissions.
Regional applicability
These findings are relevant to UK cattle producers and policy-makers seeking to reduce farm greenhouse gas intensity, particularly given domestic and European regulatory pressure on emissions. The variable efficacy reported suggests that additive selection and formulation require careful consideration within specific production systems and nutritional contexts typical of UK dairy and beef operations.
Key measures
Enteric methane production (g/day); effectiveness of feed additives; modes of action (methanogenesis inhibition vs. rumen environment modification)
Outcomes reported
The review evaluated the efficacy and modes of action of various feed additives (3-nitroxypropanol, nitrates, halogenated compounds, lipids, and plant secondary compounds) in reducing enteric methane production in cattle based on in vivo studies. Results demonstrated variable effectiveness across additive classes, with some showing substantial reductions in daily methane output whilst others produced inconsistent outcomes.
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