Agronomic performance, herbage quality, methane yield and methane emission potential of pasture mixtures

Context Enteric methane (CH4) emission from livestock accounts for 71% of greenhouse gas emissions from Australian agriculture. Aims To evaluate a range of pasture mixtures by using species with anti-methanogenic properties for their compatibility, productivity, feed quality and CH4 emission reduction potential. Methods Two field experiments were conducted at Wagga Wagga and Cowra, New South Wales, Australia, from 2022 to 2024. In total, 33 pasture mixtures were evaluated over 3 years. Herbage was taken in spring from each pasture mix to analyse mineral composition, feed quality, plant secondary compounds and CH4 yield from in vitro fermentation. Key results Methane yield was negatively correlated with saponins and condensed tannins. Perennial herbs, particularly plantain, had higher concentrations of condensed tannins and saponins than perennial grasses, at both sites. Overall, balansa clover was the species with the highest concentration of condensed tannins and biserrula had the highest concentration of saponins. However, plantain and biserrula lacked persistence at both sites. Chicory-based pastures were highly productive with high feed quality. Conclusions Pasture species higher in saponins and condensed tannins have great potential to reduce enteric CH4 emissions. Pasture mixtures containing plantain and/or biserrula exhibited potential to reduce CH4 emissions, but poor persistence may limit their adoption in some environments. Implications The study provided evidence that a number of highly productive pasture mixtures have potential to reduce CH4 emission intensity and can be deployed within extensive livestock grazing systems, allowing producers opportunity to decrease their greenhouse gas liability in emission reduction schemes.