Evaluating nutritional quality and methane production from fermentation of pasture forages grown under current and future climate conditions using near-infrared spectroscopy

Context: Improved pasture nutritional quality and reduced enteric methane production under current and projected climate conditions are essential for the meat and livestock industry. Legumes and herbs could modify the ruminal fermentation process, owing to their high nutritional quality and plant secondary compound content. Aims: This study aimed to evaluate the effects of climate stress on the nutritional quality and enteric methane (CH₄) production associated with temperate legumes (Medicago sativa, Onobrychis viciifolia, and Biserrula pelecinus), a tropical legume (Desmanthus virgatus) and a temperate herb (Cichorium intybus). Methods: Plants were grown in large polytunnels at Western Sydney University’s Pastures and Climate Extremes field facility, receiving simulated wet (La Niña) or dry (El Niño) rainfall regimes, under ambient or elevated (+3°C) temperatures. Samples were collected in multiple seasons, freeze dried and analysed using near-infrared spectroscopy to determine nutritional quality and associated methane production, and these results were validated in vitro. Key results: B. pelecinus reduced CH₄production (−85%) and C. intybus provided reduced CH₄emissions intensity. Elevated temperature and lower rainfall (Dry) treatments resulted in lower CH₄production from B. pelecinus, D. virgatus and C. intybus. Conclusions: Reductions in predicted CH₄production from fermentation were observed in multiple species under lower rainfall and elevated temperature treatments, including in the species with the lowest overall in vitro CH₄production, B. pelecinus. Implications: The benefits of using legumes and herbs to reduce pasture-based CH₄emissions and improved nutritional quality are likely to be influenced by future changes in temperature and rainfall regime.