Reducing methane emissions in sheep through breeding and genetics

While all eyes are on the dairy and beef sectors with regard to reducing methane emissions from agriculture, the sheep sector also has a role to play.

A reduction in numbers will obviously reduce sectoral emissions but this is not the preferred avenue with other options being actively worked on.

The two main avenues identified as pathways for mitigating enteric methane emissions from ruminant livestock are genetics and diet supplementation/adaption.

Diet supplementation options for sheep farmers were touched on in last week’s Signpost Programme Focus and, this week, the Sustainable Farm Insights page will review progress on the breeding and genetics front.

New breeding values

New breeding values for methane emissions were launched in June 2023 at Sheep 2023. The values are based on collaborative research between Teagasc and Sheep Ireland, taking place as part of the €3m research project, Greenbreed, which is funded by the Department of Agriculture, Food and the Marine. The research has been described as ground breaking and paves the way for €uro-Star ratings for methane to be rolled out in 2024.

A high percentage of records have been collected through the INZAC flock based in Athenry with work here led by Teagasc researcher Fiona McGovern.

Extensive records have also been collected from other research programmes in Mellows Campus and through the Teagasc BETTER Farm Sheep Programme.

Over 12,000 records

Over 12,000 records have been collected to date across 5,177 animals.

Within this, 9,464 records (4,966) have been collected outdoors which is a major development in terms of being able to quantify methane emissions from grass-based production.

The records were also collected across 14 counties, which gives a good geographical spread and widens the research out across a range of production systems.

Table 1 details records collected by animal type. The reasoning for such a large number of ewe records is that targeting ewes post-weaning facilitated a more straightforward approach to scale up the number of records that could be recorded.

Table 2 details the phenotypic correlation of co-efficients while Table 3 gives a snapshot of results to date. As can be seen, there is a strong heritability and repeatability.

A high correlation of 0.72 for the ewe datasets shows that measurements can be carried out in lactating or dry ewes. Methane values provide the ability for ranking rather than being absolute values.

Key research findings include large differences in daily methane emissions found between ewes with 17% of these differences traced to genetics.

The genetically identified highest 20% of emitting animals are expected to emit 15% more methane per day compared to the lowest 20% emitting animals.

Some differences have been found between the main breeds in terms of methane output but there is greater variation within breed than across breed. This shows that there is significant scope for all breeds to achieve genetic gain for methane emissions.

The nature of the research carried out to date is very extensive and requires huge input in terms of finances and labour.

Fiona explains that the aim now is to use predictor traits to be able to collect similar information without research techniques and continue to scale up the number of records feeding into evaluations.

Work is ongoing in determining the relationships between methane output and animal production traits, with PhD student Edel O’Connor completing much of the work to facilitate the collection of data from PAC chambers.

Recent research has looked at CT scanning as a proxy for total meat yield, methane measurements (PAC chambers), rumen sampling and carcase and meat quality data. The ultimate aim is the development of a carbon sub-index that sheep breeders can use to make informed decisions.

Fiona explains that incorporating such measures into genetic evaluations will also encourage breeders to select for genetics that reduce methane emissions without negatively affecting an animal’s performance and profitability.

The methane breeding values are available on genotyped animals through www.ramsearch.ie.

There has been much discussion and debate in recent years following the introduction of the INZAC trial as to whether importing animals can enhance the rate of genetic gain.

Fiona highlights that results from gene flow modelling carried out by the now qualified PhD student Nicola Fetherstone show that if the sector focuses on the continuous use of high genetic merit animals and selects internally rather than importing new genetics then far greater genetic gain is possible.

This is not to say that there is not a place for the strategic importation of new genetics in to the Irish gene pool but rather that focusing on the importation of new genetics will slow the rate of genetic improvement.

An analysis of phenotypic performance of recorded animals from 2010 to 2022 shows that the average number of lambs born has increased by 0.12 lambs and lamb mortality has reduced by 3.65%, while ewe mature liveweight has reduced by 5kg without affecting weaning weight which has increased by 2.3kg.