Grass management (methane emissions)

Last update: 2 June 2023

• Action: Reduction of enteric methane emission.
• Animal category: All ruminants.
• Technique: Improve quality and digestibility of grass via decreasing grass maturity through better grazing management and early cutting of grass for conservation as silage or hay.
• Mode of action: Decreasing grass maturity results in greater digestible energy and protein content.
• Potential efficacy: 13% abatement of enteric CH4 emissions per kg milk on average.
• Nature of evidence of efficacy: Peer-reviewed scientific publications (meta-analysis).
• Factors impacting on efficacy: Plant species; variety; maturity at harvest and preservation can affect forage quality and digestibility.
• Mode of use: Grazing or conservation as hay or silage.
• Requirements/limitations: Applicable in all grass-based production systems; requires good knowledge of local agronomic conditions and careful management by farmers.
• Economic consequences: Reduction of grass yield compensated partially by higher forage efficiency and increased milk yield.
• Other considerations: The higher protein content in grass may increase nitrogen excretion; this can be mitigated by combining with low protein concentrate to optimize overall nitrogen content in the diet; possible synergies with legume grass and tanniferous forages.
• References:
  • Arndt et al. (2022). Full adoption of the most effective strategies to mitigate methane emissions by ruminants can help meet the 1.5 °C target by 2030 but not 2050. PNAS May 10, 2022. https://doi.org/10.1073/pnas.2111294119
  • Van Middelaar et al. (2014). Cost-effectiveness of feeding strategies to reduce greenhouse gas emissions from dairy farming. J. Dairy Sci. 97 :2427–2439. http://dx.doi.org/10.3168/jds.2013-7648
  • Brask et al. (2013). Enteric methane production, digestibility and rumen fermentation in dairy cows fed different forages with and without rapeseed fat supplementation. Anim. Feed Sci. Technol. 184, 67-79 (2013). https://doi.org/10.1016/j.anifeedsci.2013.06.006
  • FAO (2023). FAO LEAP guidelines on Methane emissions in livestock and rice systems: Sources, quantification, mitigation and metrics.
  • EIP-AGRI Focus Group (2017). Reducing emissions from cattle farming.
• Other techniques: Unsaturated fat sources (linseed, rapeseed fat); electron sink (nitrate); methane inhibitors (Asparagopsis taxiformis, 3-NOP, tanniferous forages); shift in rumen fermentation pattern (tannins, probiotics, organic acids, essential oils, decreasing forage-to-concentrate ratio); lower emission intensity (increasing feeding level, increasing feed efficiency, decreasing grass maturity).