Antimethanogenic bioactivity of Australian plants for grazing systems

Summary

​We investigated the 'antimethanogenic' bioactivity of a range of fodder plants, plant extracts and selected feed additives. We also investigated the variability, persistency and mechanisms behind this bioactivity, using a lab-based system. We identified a range of tropical legumes (e.g. Leucaena leucocephala, Desmanthus virgatus), novel forages (e.g. turnip and chicory), plant extracts (e.g. Eremophila glabra, Santalum spicatum) and feed additives (e.g. grape marc or marine products – DHA and Nannochloropsis oculata), that have the potential to reduce methane in the rumen. We also demonstrated that, under laboratory conditions, one plant (E. glabra), reduced methane by directly affecting the methanogens in the rumen. This effect persisted over several weeks and we are now conducting a study to confirm it works in sheep. We purified specific fractions that are responsible for these effects, which will help lead us to the specific compounds that are antimethanogenic and the mechanism behind their action. Most variability in anitmethanogenic bioactivity was observed when plants were grown at different locations and between different plant accessions within a species. Season, phenology and grazing had less influence on the variability. Our results will assist in developing new grazing and management systems for reducing methane emissions from grazing ruminants.​