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In vitro screening of temperate grasses, legumes, and herbs for anti-methanogenic potential and fermentation profile for Australian dairy systems

Dilini Chamindika Weerathunga , Aodan Neachtain, Khageswor Giri, Long Cheng, Anna Thomson , Joe Jacobs, Kevin Smith

Abstract

Context. Grazing-based dairy systems in Australia are a major source of enteric methane production that contributes to global greenhouse gas emissions. Enhancing pasture quality and incorporating lower methane yielding pasture species into ruminant production systems are dietary manipulation strategies for methane mitigation. Aims. Samples of twelve temperate pasture species collected during Spring and Autumn in medium and high-rainfall temperate dairy grazing systems in Victoria, Australia were screened for their antimethanogenic potential and fermentation profiles during Spring and Autumn in medium and high-rainfall temperate dairy grazing systems in Victoria, Australia. Methods. Pasture species (four grasses, four legumes and four herbs) were harvested at a grazing-ready, vegetative, growth stage from farms in the region of either Ellinbank or Hamilton, VIC, Australia, and oven dried at 60°C for 72 h. Ground samples were analysed for their nutritive characteristics and in vitro fermentation characteristics, including methane, volatile fatty acid and ammonia nitrogen production. Key results. Fermentation of legumes resulted in higher total volatile fatty acid concentrations, ammonia nitrogen production and methane production across seasons compared to grasses and herbs (P < 0.01). The herbs burnet (Sanguisorba minor) and yarrow (Achillea millefolium) reduced methane production by 40 to 50% and methane as a proportion of total gas by 20 to 35%, across seasons, compared to perennial ryegrass (Lolium perenne L). Similarly, burnet and yarrow had the lowest total volatile fatty acid production across both seasons (78.80 and 78.05 mM respectively; P < 0.001). Principal component analysis revealed a positive relationship between methane and total gas production and total volatile fatty acids, and a negative relationship with fibre fractions. Conclusions. Both burnet and yarrow were identified as promising species for enteric methane mitigation, likely due to their plant secondary compound profiles. Implications. Burnet and yarrow are currently uncommon in temperate dairy systems in Australia, however, based on these findings, they should be investigated further for their promising methane mitigation properties. If results can be confirmed in vivo, combining burnet and yarrow into Australian temperate pasture systems would be a cost-effective strategy that farmers could adopt in order to work towards industry greenhouse gas reduction targets.

AN25199  Accepted 18 October 2025

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