Measuring methane

Teagasc researchers are establishing a technique that allows them to rank sheep based on methane output, in order to generate breeding values for methane production.

Photography: Andrew Downes

Over half of Ireland’s agricultural greenhouse gas emissions (GHG) are made up of methane – the direct output from the digestive process in ruminants (mammals with multiple stomachs, such as cattle and sheep). To support Ireland’s national Climate Action Plan, a better understanding of methane production is needed, in order to develop mitigation strategies.

Since 2019, researchers from Teagasc’s Animal and Bioscience Research Department have been comparing methane measurement methods, in order to establish a technique that allows them to rank animals based on methane output. Particular focus is being given to the portable accumulation chambers (PAC) method, which places sheep in a chamber and measures their methane output at a point in time.

Here, Research Officer Fiona McGovern, Senior Research Officer Noirin McHugh, Research Technician Eoin Dunne and Teagasc Walsh Scholar Edel O’Connor (Animal and Bioscience Research Department) discuss the results of their method comparisons and why using PAC is an exciting development for the future of the sheep sector.

What are the methods you’re comparing for methane measurement?

Fiona McGovern: We’ve used portable PAC, sulphur hexafluoride (SF6) and respiration chambers. The main measurement technique we use is the PAC, and the other two were used to validate PAC initially.

Why is establishing a technique to measure methane in sheep production systems important?

Fiona: Our goal is to collect data to generate breeding values for methane production in sheep. We have developed a standard operating procedure for using the PAC in Ireland, and to date, over 3,500 genotyped animals have been measured on farms across the country.

The data will enable the construction of a methane breeding value for sheep in Ireland, which will be incorporated into an Irish sheep genetic index. 

What does each method involve?

Edel O’Connor: The PAC is an aluminium box that sheep are placed in for 50 minutes, with methane, oxygen and carbon dioxide measurements taken at three time points. It has the capacity to measure 72 animals per day, and allows us to identify high and low methane-emitting sheep in the flock.

Respiration chambers are considered the gold standard of methane measurement as they’re very accurate. They are airtight cabins that can measure an animal’s methane production over a period of two to four days. Unlike PAC chambers, however, they have limited capacity.

Eoin Dunne: Our third method, the SF6 tracer, releases a known rate of SF6 gas from a tube in the animal’s stomach, and samples of exhaled breath are collected in an evacuated canister over a 24-hour measurement period. This method allows methane production to be measured from sheep in their natural environment.

What are some of the key findings from your work so far?

Edel: We have found that there is a good relationship between methane production measured using both the PAC and the respiration chamber. This means the animals are likely to be ranked the same, irrespective of the measurement technique used.

This result highlights the suitability of the PAC as a measurement technique that will not only allow for a higher throughput of animals, but also allow animals’ methane production to be measured in their natural environment.

Have any of the results surprised you?

Noirin McHugh: Edel is conducting work to determine how methane production differs depending on life stage and stage of production. What we’ve seen so far is that about 30% of the differences in methane output between two animals is purely down to genetics and not related to diet type, breed or life stage.

This is great news as it means we can make rapid progress in identifying animals with good levels of animal performance but lower levels of methane emissions.

Is there anything novel about the work you’re doing?

Edel: Our use of PAC to measure methane production is quite unique to our geography – across the world, New Zealand and Australia are the two main countries using PAC in this way. Like New Zealand, we will develop our own genetic breeding values, making us one of the first countries in the northern hemisphere to achieve this.

Noirin: In Ireland, our work is unique because Teagasc is currently the only group looking directly at methane emissions from sheep systems. As such, we work very closely with Sheep Ireland – the company responsible for the national genetic evaluations in Ireland – to make sure that our research can be implemented quickly into Ireland’s breeding indexes.

How have farmers reacted to your work?

Eoin: I have been measuring animals using the PAC on farms over the past few months, and it has been a great experience. Farmers are very accommodating and enthusiastic about the results.

This is a novel line of work in terms of the sheep sector, which has brought about challenges regarding the mentality of some farmers who see it as unnecessary, but our goal is to make farmers aware of our current situation regarding greenhouse gas emissions and to help them develop mitigation strategies.

What are the benefits of this project?

Noirin: This project has huge implications for the Irish sheep industry. If we can show that we are able to select animals with lower levels of methane emissions while still maintaining high levels of production, we can help to reduce the carbon footprint of the industry.

What’s next for your research?

Fiona: We need to extend research into strategies that improve efficiency and reduce farm GHG emissions. Data we obtain can feed into our national GHG inventories and determine the impact of pasture type and quality on methane output in sheep.

Noirin: We will also look to implement our research findings into the national genetic evaluations. Doing this will enable Irish sheep farmers to select animals with lower levels of methane emissions that will also help to increase flock performance and profitability. 

In good company

What do you find most interesting about this type of research?

Edel: For me, the most interesting part of this research is seeing how an animal’s methane production changes throughout their production cycle and at different life stages.

Fiona: This research is innovative and of national importance, with major impacts for ruminant animal production systems – especially sheep. Results generated will facilitate management decisions and promote profitability on sheep farms nationally.

Nóirín: This is groundbreaking research and has major implications for the Irish sheep industry – our results can help to increase its long-term viability.

Eoin: What I find most interesting is how progressive this field of work has become in Ireland in recent years. We are advancing at a very quick rate, and it is becoming more accepted and appreciated by farmers across Ireland.

Measuring methane from sheep systems