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Low Emissions Livestock Breeding – The What and the Why

8 July 2024

In 2020, agriculture contributed 18% of Scotland’s total Greenhouse Gas (GHG) emissions. Methane emissions from ruminants contribute around 50% of this total. With aims to achieve Net Zero carbon emissions by 2045, various technological innovations are being developed and trialled to reduce the emissions intensity of livestock. One promising area is selective breeding which can reduce methane intensity by 24% in 2050 if such trait is incorporated in breeding goals. This method is gaining growing interest as future subsidy payments linked to low carbon farming measures and net zero targets continue to put pressure on farmers and industry partners to decarbonize. DEFRA awarded £2.9 million under their Farming Innovation Programme for a three year project to measure flocks and develop tools to breed sheep with a lower carbon footprint. This article will provide an overview of current research and potential commercial uptake of this innovation in the sheep sector.

What is low emissions breeding?

When it comes to breeding and genetic solutions in mitigation emissions, the two-prong approach is improving the feed efficiency and productivity of animals. Efficient and productive livestock would require less feed to grow and yield the same output, thus lowering waste and emissions per kg of product. Alternatively, livestock can be bred directly to reduce methane emissions. The process requires individual sheep to be measured based on these attributes and to breed individuals that possess these desirable qualities. By selecting productive and low emitting individuals, each generation will cumulatively become more efficient, thus lowering the average carbon footprint of sheep across generations.

What are the developments in this field?

Worldwide, research is at different stages as more information (e.g. genetics, feed intake, and methane emissions) is needed to build a sufficient database to estimate genomic* breeding values and implement genomic selection. In New Zealand, where selective breeding started with flocks of low and high emitting sheep since 2008, the low emitting sheep flock differed by 16% within two additional generations. Their research confirms that  methane emissions as a trait is heritable. In 2019, breeding values for methane emissions were made available to selected breeders.  In the UK, research is in the evidence gathering stage with plans to measure 13,500 sheep across 45 flocks under Breed for CH4nge programme. Studies in Wales and Ireland also show potential in mitigating emissions from sheep through selective breeding.

* Genomics encompasses complete genetic information of an organism, whereas genetics is the study of function and composition of single genes.
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How are sheep measured for low emissions breeding?

There are a number of ways to measure or predict emissions from individual animals. Examples include:

  1. Feed intake measurements such as automated feed intake recording equipment,
  2. GHG emissions measurements to analyse concentrations of methane and carbon dioxide,
  3. Rumen morphology
  4. Rumen microbiome analysis

Ruminants like sheep and cattle have diverse microbes in their stomachs that ferment feed to digest it. Enteric methane is a by-product of this process that is released via belches, contributing to 30% of methane emissions into the atmosphere each day. Manipulation of these microbes and subsequently breeding treated animals can reduce methane emissions in the next generation. To measure rumen function, CT scanning or post mortem measurements can be conducted to look at morphology, such as rumen volume, whereas rumen microbial analysis would involve stomach tubing for sample collection. Blood plasma measurements could also be taken to measure the volatile fatty acid (VFA) concentration (formed from fermentation of feed) to predict methane emissions.  These methods are invasive and would require lab analysis or equipment off-site.

There are various tools to capture gas samples from livestock. These range from “sniffer” gas analysers to hand-held laser methane detectors* and more accurate, flux-based emissions measurement such as GreenFeed. It is a challenge to record feed consumption and emissions on an individual basis, especially in Scotland’s grass-fed sheep system. It requires measurement tools that work outdoors, mobile, and have little impact on animals and on-farm routine. One promising technology in this space are Portable Accumulation Chambers (PACs). Sheep are individually enclosed in an aluminium chamber where methane and carbon emissions along with live weight are measured. The process takes 50 minutes and can measure animals straight from pasture. Study shows results are moderately repeatable across diets and feeding levels as well. Other breeding traits (e.g. growth rate, maternal traits, carcass quality) can also be monitored in the pedigree-recorded flocks where these measurements are being taken, with the aim to enable a genetic selection programme that optimizes all important breeding goals simultaneously.

* Guidelines for estimating methane emissions from individual ruminants using GreenFeed 'sniffers' hand-held laser detector and portable accumulation chambers (2020)- ResearchGate

What are the benefits?

A study published in 2011 on Welsh sheep predicted 0.5% and 1.3% methane reduction for hill and lowland sheep over a 10 year period when breeding for traits associated with productivity (e.g. ewe litter size, carcass weight, lamb growth weight). This is also echoed in Sheep Ireland and Teagasc’s research that revealed 5% reduction in GHG emissions for high performing flock. Low emissions breeding aimed at improving productivity can both reduce methane emissions and deliver economic benefits as well. The study revealed increased output and performance equates to 23% less GHG emissions per €1,000 net profit.

There were diverging results as well. A study on Scottish Blackface sheep flocks predicted GHG emissions per kg for upland and lowland sheep to decrease, but for hill sheep this would likely increase instead due to larger ewe size at maturity. A possible explanation is due to their larger rumen that’s adapted to process poor quality vegetation. More developed breeds in low ground systems tend to have smaller rumens. Research is ongoing to understand the correlation between rumen size and methane emissions.

The table below summarises research findings on heritable traits and their correlation with methane emissions:

TraitGenetic HeritabilityIs there correlation with lower methane and carbon dioxide emissions?
Feed intake and efficiencyLow-ModerateYes[1]
Rumen volumeModerateMore research needed to confirm relationship[2]
Rumen microbial profileModerateYes[3]
Volatile fatty acid concentrationModerateYes but depends on diet[4]
[1] Repeatabilities, heritabilities and correlations of methane and feed intake of sheep in respiration and portable chambers (2020)- CSIRO Publishing ; More feed efficient sheep produce less methane and carbon dioxide when eating high-quality pellets (2017)- Oxford Academic ; Models for estimating feed intake in small ruminants (2013) – SCIELO Brasil
[2] Variation in reticulo-rumen volumes between and within sheep breeds and genetic relationships with production traits (2022)- CSIRO Publishing
[3] Breeding Low Emitting Ruminants: Predicting Methane from Microbes (2019)- MDPI
[4] Genetic parameters of plasma and ruminal volatile fatty acids in sheep fed alfalfa pellets and genetic correlations with enteric methane emissions (2019) -Oxford Academic

What at the limitations?

Although studies show potential to reduce methane emissions directly with breeding, current breeding goals do not include feed intake or methane emissions in their genetic selection index weightings. However, to gain commercial and policy confidence, predictions need to be sufficiently reliable. This means animals need to be widely phenotyped and genotyped to build a robust database. Breeding is complex and variations within individuals could be due to various environmental factors, grass or feed quality. Thus, with more records and data collected, the more accurate estimation of breeding values can be. Methods to measure individual sheep emissions are also costly and require equipment or laboratory processes, which limit their wider commercial uptake among farmers. However, work is underway to find more commercially-relevant strategies to include methane emissions in breeding goals for livestock breeders.

Where can I find out more?

SRUC is currently trailing its own PACs. If you’d like to learn more about this technology, or explore opportunities to use on-farm, read this article here.

Want to learn more about UK’s progress in this space? Visit Breed For CH4nge’s website here.

If you’d like to learn more about this topic, the 2011 study by Hybu Cig Cymru is a useful resource and can be found here.

Nicola Lambe, SRUC

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