USING NUTRITIONAL STRATEGIES TO MITIGATE RUMINAL METHANE EMISSIONS FROM RUMINANTS

Abstract

<List> <ListItem> <ItemContent> ● Microbial fermentation in the rumen is a main source of methane emissions. </ItemContent> </ListItem> <ListItem> <ItemContent> ● Nutritional strategies can effectively mitigate methane emissions by manipulating biochemical reactions in the methanogenesis pathways. </ItemContent> </ListItem> <ListItem> <ItemContent> ● Mitigation practices must be evaluated in an integrated animal production system instead of as isolated components. </ItemContent> </ListItem> </List> Within the agricultural sector, animal production contributes to 14.5% of global anthropogenic greenhouse gas emissions and produces around 37% of global CH₄ emissions, mainly due to ruminal fermentation in ruminants. Over 90% of CH₄ is synthesized by methanogens in the rumen during carbohydrate fermentation. According to different substrates, methanogenesis pathways can be divided into four categories: (1) hydrogenotrophic pathway; (2) acetoclastic pathway; (3) methyl dismutation pathway; and (4) methyl-reducing pathway. Based on the principle of biochemical reactions in the methanogenesis pathways, this paper reviews the latest publications on CH₄ decreases in ruminants and described three nutritional strategies in terms of dietary nutrient manipulation (feeding management, feed composition, forage quality and lipids), microbial manipulation (ionophore, defaunation, methanogen inhibitors and probiotics), and chemical manipulation (nitrate, organic acids, plant secondary metabolites and phlorotannins, or halides in seaweeds). For each mitigation strategy, the review discusses effectiveness for decreasing CH₄ emissions, application prescription, and feed safety based on results from <i>in vitro</i> and <i>in vivo</i> studies. This review summarizes different nutritional strategies to mitigate CH₄ emissions and proposed comprehensive approaches for future feeding interventions and applications in the livestock industry.