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Plantain-mixed pasture collected in different climatic seasons produced less methane and ammonia than ryegrass-white clover pasture in vitro

Komahan Sivanandarajah , Daniel Donaghy, German Molano, David Horne, Peter Kemp, Soledad Navarrete, Thiagarajah Ramilan, David Pacheco

Abstract

Context. Plantain (PL) is recognised for reducing nitrate leaching and nitrous oxide emissions in pastoral systems. Evidence has shown that cows fed pure PL produced less methane (CH₄) than cows fed ryegrass. However, it is unclear if the CH₄ reduction can be achieved with PL in mixed pasture. Aim. The study evaluated the in vitro rumen fermentation profiles of ryegrass-white clover (RWC) and medium-level PL (PLM, containing ~40% PL) pasture collected during different climatic seasons, to determine whether this inclusion level influences CH₄ and rumen ammonia (NH₃) production. Methods. Substrates were selected from samples with various proportions of PL. Samples were categorised into three climatic seasons (i.e., spring, summer, and autumn) and two pasture types (PLM and RWC). Representative samples for these scenarios were tested in an automated in vitro rumen batch culture system for gas, CH₄ (mL/g DM) and NH₃ (mmol/g DM) production. Key results. In summer samples, PLM produced around 8%, 14%, and 19% less CH₄ at 12 hours, 24 hours, and potential CH₄ production (PCH4), respectively (p<0.05). Although gas production (GP) was similar at 12 and 24 hours, PLM had 13% lower potential GP (PGP) than RWC (p<0.05). In spring samples, PLM had around 11% greater GP and CH₄ production at 12 hours. For the autumn samples, GP and CH₄ production were similar between PLM and RWC (p>0.05). Net NH₃ production from PLM substrates was significantly lower in spring (27%) and autumn (17%) samples, with no differences in summer despite higher crude protein levels in the selected PLM. Conclusions. Compared to RWC, PLM changed rumen fermentation parameters that could translate to potential environmental benefits: PLM produced less net NH₃ in spring and autumn samples (27% and 17%, respectively) and up to 19% less CH₄ production in summer samples. Implications. Incorporating ~40% PL into RWC pasture showed promising reduction of CH₄ emissions and nitrogen losses in vitro. If the in vitro results translate to cows grazing pasture this could offer greater environmental benefits with minimal input costs. In vitro results suggest that PLM’s potential to mitigate CH₄ emissions can be influenced by seasonal variations in pasture quality compared to RWC. However, further animal studies are needed to fully comprehend the CH₄ mitigation potential of this forage.

AN24287  Accepted 31 May 2025

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