The potential to reduce methane emissions from grazing livestock in Australia

Context Methane emissions from grazing livestock are of concern to the red meat industry because they are a major source of greenhouse gases (GHGs), may restrict future market access, and negatively affect consumer perceptions of the industry. Some pasture species when grazed reduce methane production in the rumen, potentially reducing GHG emissions from grazing livestock. Aim To review the potential of pasture species to reduce methane from ruminants, evaluate the adoptability of the most promising low-emissions pasture species, and forecast the likely changes to red meat sector GHG emissions by using a simple production and adoption model. Methods A global search for plant species suitable for grazing and that reduce methane production and/or yield, both in vitro and in vivo, was conducted using the Web of Science database. Data on methane reduction from individual plants were categorised according to species type and measurement technique. Selection of plant species for further consideration as prospective or minor-use low-emissions forages was based on their agronomic requirements and suitability as livestock feeds within three bioregions of tropical, temperate and Mediterranean. A simple adoption model was developed and used to estimate likely changes in methane production, yield and intensity across Australia following adoption of low-emissions species. Key results Seven prospective species (lucerne (Medicago sativa), brassicas, plantain (Plantago), Leucaena, Stylosanthes, Desmanthus, and biserrula (Astragalus pelecinus)) and three minor-use species (high sugar ryegrasses (Lolium), sainfoin (Onobrychis vicciifolia) and Rhagodia)) were selected as species that were most likely to reduce grazing emissions. It was concluded that the opportunity for plant species to reduce methane from grazing livestock was modest. Nevertheless, when adopted across large numbers of livestock, they can make a useful contribution towards reducing methane emissions from the grazing sector. Conclusion The intensity of emissions per unit of animal product is likely to be reduced, whereas total emissions per area may increase following adoption of low-emissions forages. The lack of scientific information on methane dynamics under commercial field conditions hampers the development of methane avoidance methods and further research is required. Implications Adoption of low-emissions forages improved pasture productivity while reducing the intensity of methane emissions from grazing livestock.