Management of Enteric Methane Emissions in Ruminants Using Feed Additives: A Review

SIMPLE SUMMARY: Methane emission from enteric fermentation in ruminants is the single most relevant greenhouse gas source in agriculture, and it is amongst the largest anthropogenic ones. As ruminants are needed globally for meat, milk and other goods production on a huge scale, feed additives could offer an interesting solution to reduce CH(4) emissions. Methane emission strategies are investigated to maintaining productivity and the overall health of the animal. Some strategies have shown to reduce the propagation and/or eliminate ruminal flora affecting the health and productivity of the animal. Therefore, identifying beneficial strategies leads to improving productivity and the health of the animal and environment. ABSTRACT: In ruminants’ metabolism, a surplus of hydrogen is removed from the reduction reaction of NAD(+) (nicotinamide adenine dinucleotide) by the formation of methane by methanogenic bacteria and archaea methanogens. The balance of calculations between VFA (volatile fatty acids), CO(2), and CH(4) indicates that acetate and butyrate play a role in methane production, while the formation of propionate maintains hydrogen and therefore reduces methane production. CH(4) formation in ruminant livestock is not desired because it reduces feed efficiency and contributes to global warming. Therefore, numerous strategies have been investigated to mitigate methane production in ruminants. This review focuses on feed additives which have the capability of reducing methane emissions in ruminants. Due to the environmental importance of methane emissions, such studies are needed to make milk and meat production more sustainable. Additionally, the additives which have no adverse effects on rumen microbial population and where the reduction effects are a result of their hydrogen sink property, are the best reduction methods. Methane inhibitors have shown such a property in most cases. More work is needed to bring methane-reducing agents in ruminant diets to full market maturity, so that farmers can reap feed cost savings and simultaneously achieve environmental benefits.