Methane emissions lower than expected during spring

New results from the Emissions4Pasture programme are giving farmers and scientists a clearer picture of methane emissions from grazing cows – and early results suggest they’re lower than current predictions, particularly during spring.

Emissions4Pasture is a New Zealand– Ireland partnership funded by DairyNZ, MPI, the Ag Emissions Centre and Ireland’s Department of Agriculture (DAFM), with research delivered by DairyNZ, Teagasc, University College Cork and the Irish Cattle Breeding Federation. A key focus is to understand methane emissions from grazing cows throughout the year.

See how methane changes through the year

Farmers see seasonal changes on their farms. In spring, pasture is leafy and highly digestible; summer feed is often drier and more fibrous; and cooler months affect pasture growth and cows’ energy requirements. These differences influence how much cows eat, how they digest feed and how much methane they produce.

Emissions4Pasture is asking two key questions:

• Do methane emissions change across the seasons?
• Are these changes driven by cow factors, pasture factors, or both?

Building a complete seasonal picture helps identify when methane emissions are naturally lower or higher, and why.

Spring surprises: methane lower than predicted

The first dataset – spring 2024 – shows methane emissions were about 20% lower than the default value currently used in national and milk processor inventories.

PhD student Jessica Dalton, who is working with DairyNZ scientists Dr Jane Kay and Dr Konagh Garrett on the seasonal analysis, says the lower methane yield was strongly linked to good-quality spring pasture, which is leafy, digestible and low in fibre.

“What we’re seeing in New Zealand mirrors Irish and Dutch findings,” Jess says.

“It suggests grazing cows may produce less methane than predicted throughout the year, and particularly during spring.”

What this means for your farm

If methane yields are lower than predicted, the current national inventory and processor calculators may be overestimating emissions. Any updated methane factor would apply to past and present calculations, lowering both current and baseline emissions. That means it wouldn’t count as a reduction but would give a more accurate picture of how efficient our systems really are – helping keep NZ recognised as one of the world’s leading low-emission dairy producers.

Knowing how much methane is produced and when means mitigation strategies can be used where they will deliver the greatest impact.

If methane emissions are naturally lowest on high-quality spring pasture, mitigation strategies – such as feed additives, low-emissions forages, or grazing approaches – could be more effective in other periods, like summer or autumn, rather than applied year-round. This could improve both value for money and overall impact.

Next steps in seasonal research

Jess is in Ireland collecting more seasonal data, effectively getting two springs in one year, to strengthen the seasonal information and assess pasture management effects. The wider programme is also researching the impact of clover, plantain and mitigation technologies across seasons.

Meanwhile, analysis of NZ’s full dataset (spring, summer, autumn and winter) is underway. This will produce the first complete pasture-based seasonal methane profile for NZ dairy systems.

The full dataset will help refine national methane values, identify seasonal ‘hot spots’, and support practical, targeted mitigation strategies, strengthening the accuracy and credibility of NZ’s low-emissions dairy story.

To keep up to date with the latest research, visit dairynz.co.nz/pasture-emissions