Sophie Doran

Methane is produced by microbial fermentation in the rumen. It is a potent greenhouse gas and its production requires energy, resulting in production losses from ruminant livestock. Accurately measuring methane production by ruminants presents difficulties due to considerable variation between animals, depending on factors such as diet and body weight. Although the "gold standard" method for measuring ruminant methane output is the use of methane chambers, this is too time consuming and labour intensive to be used in large-scale on-farm situations.

This project aims to develop proxies, which can be used to estimate methane output by sheep at an on-farm scale.

The potential proxies to be investigated during this project include the methane potentials of various feeds, obtained using an in vitro gas production technique and a selection of plants is currently being collected on a monthly basis for this purpose. The use of a laser methane detector (LMD), which uses infrared spectroscopy to give measurements for methane concentration in the column of gas, is also being explored. Finally, the detection of archaeol, a membrane lipid of the methanogenic archaea, in faeces is another potential proxy.

Methane emissions from sheep are being measured using the chamber technique, and these are being used to calibrate methane production measured using the proxy techniques under investigation.  Results to date indicate that the LMD is sensitive enough to detect eructation peaks of methane from the animal's mouth as well as normal breath concentrations, and investigations are currently focussed on the length of time required to achieve  representative data from individual animals, and whether environmental measurements (i.e. from the sheep's surroundings) provide useful data.