Measuring methane emissions from sheep

Livestock farmers across the country are under increasing pressure to optimise resource use efficiency and reduce greenhouse gas (GHG) emissions, and specifically methane, from ruminant livestock production systems.

DR

NICOLA LAMBE, SHEEP GENETICIST, SRUC

Globally, sheep release around 700 million tonnes of methane into the atmosphere per year (FAOSTAT 2020).

Carbon calculators currently do not account for differences between individual sheep in methane production. However, research has shown that there is variation between sheep, even within a flock, in the amount of methane they produce on the same diet and at the same live weight. Methane emissions are partly under genetic control and so could be changed over time by selective breeding.

Therefore, if producers are likely to be rewarded in the future for reducing (or penalised for increasing) methane emissions from their flocks, it is even more important that we are in a position to measure these emissions, particularly from sheep managed on typical UK grass-based systems.

One answer to the problem could be Portable accumulation chambers (PACs) which can be used to rapidly measure methane and other gas emissions from individual sheep kept in a variety of systems, including at pasture.

PACs are aluminium boxes, approximately 1m long with a window on the front. Twelve of these compartments are mounted on a trailer that can be towed to different locations to measure the sheep on-site. Each compartment houses an individual sheep for a short period of time (50 minutes), during which air samples are collected and methane concentration can be analysed and daily emissions predicted from each sheep.

SRUC has purchased a portable set of 12 PACs, mounted on a trailer, from AgResearch in New Zealand, who have developed and tested the design. The aim is to use this equipment in our research, by measuring a variety of sheep from different breeds and systems in the UK.

So far, measurements of methane have been taken on some Scottish Blackface hoggets from our SRUC hill flock and from a small number of commercial breeders’ farms in England with a variety of maternal and terminal sire breeds. Results have confirmed that methane emissions from sheep are feasible to measure on-farm using PACs, under UK conditions, and there is variability between animals in methane emissions recorded by PACs that could potentially be exploited within breeding programmes.

Dr Nicola Lambe from SRUC, who is coordinating the PAC research said: “There is an urgent need to mitigate greenhouse gas emissions from sheep. Despite the fact that resource efficiency and greenhouse gas emissions are global priorities, there are few examples around the world of breeding strategies being implemented in practice to directly tackle these issues in sheep.

“This is largely due to the difficulty in recording feed consumption and greenhouse gas emissions on an individual animal basis, especially in grazing production systems. The Portable Accumulation Chambers will play an important role in starting to address this issue.”

Working with Agri-EPI Centre, Rob Hodgkins, who has 2,500 sheep on his farm in Hertfordshire, has become the first farmer in the UK to use the PACs, following a grant from Innovate UK.

He said: “Not only does this make sense from an environmental point of view, but it also makes sense economically. It will only be a matter of time before consumers will be able to look at labels on packets of meat that shows what they are buying has come from, for example, a carbon-zero sheep.”

The next steps are to collect PAC measurements of methane from more well-recorded sheep across generations, in order to investigate the genetic control of emissions in UK sheep and genetic relationships with other important traits. This will allow us to assess the feasibility of incorporating methane measurements into breeding programmes for UK sheep to help met Net Zero targets.

Get in touch

nicola.lambe@sruc.ac.uk