Emissions4Pasture

About the research

Emissions4Pasture is a four-year collaborative research programme (2024 to 2028) between New Zealand and Ireland. It aims to improve how methane emissions from dairy cows in pasture-based systems are measured and understood.

It will also develop more precise emissions factors for pasture-based systems to improve farm and national-level accounting in both countries, which face methane reduction targets.

Currently, greenhouse gas inventories use a standard methane emissions factor for all feed eaten by a dairy cow. In New Zealand, this factor predicts that for every kilogram of dry matter that a cow eats, 21.6g of methane is produced. A similar approach is used in Ireland.

However, although feed is a major factor driving methane emissions, not all feeds are created equal. Different types, qualities and amounts of feed lead to varying levels of methane production. We are interested in exploring how this plays out within our pasture-based system.

Recent research from Ireland supports this variation, showing that cows grazing in spring produce less methane than expected based on inventory calculations, and less than they do in summer and autumn. Emissions4Pasture is testing whether similar patterns occur in New Zealand and whether the variation in methane is due to the pasture itself or connected to cows being in early lactation.

Progress update

Trial 1: Measuring methane from cows grazing pastures during the season (New Zealand)

This will involve using two herds at one of the DairyNZ research farms in Hamilton, an autumn-calving herd and a spring-calving herd. Starting in August 2024, we are measuring methane emissions from these herds for 12 months while they are outdoors grazing pasture. At four times, spring, summer, autumn and winter, a subset of each herd will be brought into our indoor facilities to measure individual cow feed intake and methane from cows consuming fresh pasture.

Using these two herds of cows lets us see how both the cow and the pasture affect methane emissions. For example, in September/October, we will have cows in early lactation and late lactation all eating spring pasture, and in March/April we will have cows in early lactation and late lactation eating autumn pasture.

Trial 2: Measuring methane from cows grazing pastures (Ireland)

Grazing cow trials are also planned for Ireland. Beginning in spring 2026 (February), these trials will explore how different pasture species affect methane emissions and whether pasture management practices (e.g. high cover vs low cover) have an impact.

Research impact

By understanding the factors behind the differing responses of grazing cows, we can develop technology specifically tailored to pasture-based systems and optimise its use throughout the season.

The joint programme strengthens our connection with Ireland and enables NZ to leverage current and future research. It also fits within DairyNZ’s wider Reduced GHG research programme.

Read more about DairyNZ’s larger programme of work for reducing greenhouse gas here.

Research partners

This collaboration involves researchers, students, professors and database technology experts from DairyNZ and Ireland’s Agriculture and Food Development Authority (Teagasc), University College Cork and Irish Cattle Breeding Federation.

How is this project funded?

DairyNZ secured funding for this work in 2023 from the Ministry for Primary Industries (MPI) and the Ag Emissions Research Centre as part of the Joint Research Initiative between New Zealand and Ireland.

The research occurring in Ireland is funded by the Department of Agriculture, Food, and the Marine (DAFM).