Medium-chain fatty acids and their potential to reduce methanogenesis in domestic ruminants

In the wave of the Kyoto Protocol, a large effort is undertaken to find sustainable strategies for reducing greenhouse gas emissions from livestock. The present paper summarises the results of a research project, which was designed to analyse the potential of medium-chain fatty acids (MCFA) as a diet component for ruminants to inhibit rumen methanogenesis. In a series of eight in vitro and four in vivo experiments, a research strategy was pursued including: (i) a comparison of feeding coconut oil (rich in MCFA) and feeds containing long-chain unsaturated fatty acids (LCFA) with respect to their effects on rumen and total digestive tract metabolism; (ii) a search for effective MCFA feeds other than coconut oil; (iii) identification of specific MCFA effective against rumen methanogenesis; (iv) clarification of the mode of action of MCFA; and (v) revealing of dietary pre-conditions for a significant methane-suppressing effect of MCFA. The project clearly demonstrated the potential of MCFA, used either in esterified form (such as coconut oil, palm kernel oil and genetically modified canola oil) or in non-esterified form (C12:0 and C14:0), to substantially reduce methanogenesis in domestic ruminants. Detailed insight into the numerous interactions within the rumen, which will determine the extent of methanogenesis inhibition when feeding MCFA, was gained. From an assessment of the combined data, it was concluded that even with dietary proportions below 3% MCFA of C12:0 and C14:0, a 50% reduction of in vivo methane emission is possible.