Teagasc is currently establishing a technique that allows it to rank sheep based on methane output, so that breeding values for methane production can be generated.

Over half of Ireland’s agricultural greenhouse gas emissions (GHG) are made up of methane, which is a direct output from the digestive process of ruminants.

In order to develop mitigation strategies, it is very important that a better understanding of methane production is needed.

PAC chambers

To allow them to rank animals based on methane output, researchers have put a particular focus on the portable accumulation chambers (PAC) method.

This places sheep in a chamber which measures their methane output at a point in time. The PAC is an aluminium box in which sheep are placed for 50 minutes.

Methane, oxygen and carbon dioxide measurements are taken at three points in time. It has the capacity to measure 72 animals per day, therefore allowing researchers to identify high and low methane-emitting sheep in the flock.


Establishing a technique to measure methane in sheep production systems is important, as the data collected will enable the construction of a methane breeding value for sheep in Ireland, which will be incorporated into the Irish sheep genetic index.

Some interesting findings from the research include how methane production differs depending on the life stage of the animal.

Interestingly, it has been found that 30% of the differences in methane output between two animals is down to genetics alone and not related to the animal’s diet type, breed or life stage.

Teagasc’s use of PAC to measure methane also makes Ireland one of the first countries in the northern hemisphere to achieve this.