Potential of silage inoculants to mitigate methane production from the rumen: A systematic review

Methane (CH₄) emissions from enteric fermentation in ruminants represent the largest source of anthropogenic agricultural emissions, contributing significantly to global CH₄ levels. Enteric CH₄ mitigation strategies have been intensively investigated to address the detrimental effects on climate change and ruminant production characteristics. This systematic review investigated whether microbial silage inoculants could reduce CH₄ formation in the rumen microbiome, both ex vivo and in vivo, based on available literature. Two independent reviewers conducted a comprehensive search for peer-reviewed articles, without year restrictions, up to January 31, 2024. The search focused on studies reporting CH₄ gas production both in vitro and in vivo. Of 434 articles initially identified, only 10 met the quality criteria and were included in the analysis. Among the selected studies, 9 measured CH₄ production using in vitro assays, whereas one reported an in vivo trial. The majority of the experiments (70%) were conducted using cattle rumen samples, including the in vivo study involving cattle, the remainder of the experiments used rumen samples obtained from sheep. Ten bacterial species were used as inoculants across the selected studies. Lactobacillus buchneri, used in combination with additives, achieved the highest CH₄ reduction at 83%. Lactiplantibacillus plantarum also showed a significant reduction in CH₄ output, achieving a 48% decrease. Overall, 80% of the reviewed studies reported a reduction in CH₄ production by ruminant microorganisms following the application of silage microbial inoculants. These findings suggest that silage microbial inoculants hold promise as a strategy to mitigate CH₄ emissions in livestock. The limited number of studies highlights the need for further research to confirm these results and explore wider applications.