The role of genetics in reducing the environmental impact of beef and sheep

Articles by Samuel Boon and Harriet Bunning

Key Messages

• Breeding goals for production efficiency tend to be closely aligned to those delivering environmental benefits.
• In the breeding flock/herd, keeping females of optimum mature size that successfully rear lots of offspring over their lifetime will significantly reduce the carbon footprint of sheep and beef production.
• In the slaughter generation, environmental benefits are delivered by reducing days to slaughter.
• Genetic selection provides an important way to enhance these attributes. Producers should use EBVs (Estimated Breeding Values) to aid ram/bull buying decisions.
• New traits that allow direct measures of methane production are being developed.

 Background

The Climate Change Act (2008) aims to reduce greenhouse gas emissions by 80% by 2050. While carbon dioxide, nitrous oxide and methane are all important greenhouse gases, for sheep and beef producers the most important is methane.

Methane is an inevitable by-product from the fermentation process when ruminants convert forage into the meat we can consume, often on land unsuited to other forms of food production.

How can we reduce methane production?

Methane is created by microbes which break down forage in the rumen and is released when ruminants eructate (belch). The amount produced will vary with intake and the type of feed consumed, but there are also important differences between animals in the amount of methane they produce.

There are two approaches through which genetic improvement can reduce methane production.

• Direct selection to identify sheep and cattle that produce less methane per kg of feed consumed.
• Indirect selection to identify animals that improve whole flock/herd efficiency, through increased productivity, fertility, health and survival. This improves the efficiency of the lamb/beef production system, reducing methane per kg lamb/beef. Improved efficiency leads to improved profits, so this strategy is a win-win.

 Research studies and findings

Direct selection

Feed efficiency units can measure feed intake relative to increases in liveweight, thus showing differences in production efficiency that will reduce methane production. In sheep breeding programmes respiration chambers can be used to directly measure methane output. In beef breeding, the greater size of cattle means that chambers are used less frequently and sensors over feed bins that measure gas flux (e.g. GreenFeed) are more common.

In each case research has shown differences between high and low performing individuals that are under a genetic influence and can be changed through selective breeding. There is a link with feed efficiency and so selection for low emitters may also improve feed efficiency.

Example: Breed for CH4nge

AHDB are partners in Breed for CH4nge an Innovate funded project that, amongst other objectives related to reducing the carbon footprint of  lamb, will look at the practical aspects of measuring methane production using PAC (portable accumulation chambers) and the use of this new phenotype within national genetic evaluations (using genomic approaches). This project will look at the relationship between methane emissions and both feed efficiency and rumen volume (assessed using CT scanning).

Research sets a gold standard against which we can assess the performance of less direct measures remembering that in the short term these new phenotypes may prove costly to exploit in a national breeding programme.

To increase the industry impact of genetic selection we must also consider the benefits of existing tools that are already designed to enhance efficiency.

Indirect selection

There are several ways that selective breeding can reduce the intensity of methane production relative to the amount of beef or lamb produced for the consumer.

• Lifting maternal productivity

The biggest impact we can make in the sheep flock is by increasing the number of lambs produced per ewe over their working lifetime. This means selecting sheep that are genetically more prolific, express better lamb survival and have a longer productive life.  Consideration should be given to sheep capable of lambing at 12 months of age.

The number of calves produced over a cow’s lifetime is extremely important. The average number of calvings for a beef cow in the UK is just over 5; increasing this to 6 would decrease the carbon footprint of her offspring by up to 17%. Breeding values that assist in this goal include those influencing cow fertility, calving ease, calf survival and cow longevity.

• Reducing adult size

Smaller ewes produce less methane, in fact low methane producing sheep tend to have a smaller rumen, albeit one with a larger surface area. While selecting for rumen size is challenging, reducing mature size is easy. Mature size is highly heritable and easily measured, though selection to reduce mature size must be balanced against requirements to lift lamb growth rates.

The same holds true for beef cattle, where additional consideration is required to ensure that reductions in cow mature size don’t compromise calving ease when cows are mated to terminal sire breeds.

Work by AbacusBio (2019) indicates the optimum mature size in a typical UK production system is around 680kg for suckler cows; for ewes it sits between 55-65kg. In many cases breeding females on UK farms exceed these weights; this highlights another area where breeding for environmental benefits could also enhance farm revenue.

• Producing meat more efficiently

Reducing days to slaughter is a key environmental breeding goal. In the beef industry progress has been made across both suckler and dairy-beef animals. Suckler improvement is steady, but improvements in dairy-beef have accelerated significantly in the last 5-10 years. While in the past, dairy-beef calves had poorer genetics for days to slaughter, this is no longer the case.

Chart 1. Industry Genetic Trends from AHDB’s National Beef Evaluation

Genetic selection to increase the carcase yield of muscle relative to fat will also reduce the amount of methane produced per kilogram of saleable meat. These are traits we can easily enhance by using sires with high breeding values for growth and carcase traits.

• Selecting for parasite resistance in sheep

Various studies have shown that parasitized sheep tend to be higher methane emitters. In maternal breeds that record with Signet, like Lleyn and Exlana, selection for greater parasite resistance is also contributing to reducing greenhouse gases.

 

Potential Impact for Farming for the Future

The permanent, cumulative and sustainable benefits derived from genetic improvement provide a massive opportunity for the sheep and beef industry to respond to the shared challenge of delivering environmental gains.

The application of genomic technology into current breeding programs provides an opportunity to make much faster genetic progress than ever before, building on the foundation of 50 years of performance recording in the UK. Greater collaboration (with support to fund it) is needed between genetic service providers, breed societies and research organizations for this potential to be realized.

The financial and environmental benefits that can be derived through genetic selection are most clearly demonstrated in the AbacusBio report “A vision for improving the UK sheep and beef sectors through breeding over the next 10 years”.

For sheep, historic rates of genetic gain are expected to deliver annualised benefits of £14.7million per annum (over the next 20 years). In parallel, emissions intensity is expected to reduce by -0.04 kg CO2e/kg product/mated female/year; a 0.23% reduction in emissions intensity per year.

For beef, the historic rate of genetic gain will deliver annualised benefits of £6.8 million per annum (over the next 20 years). In parallel, emissions intensity is expected to reduce by -0.03 kg CO2e/kg product/mated female/year; a 0.13% reduction in emissions intensity per year.

While the environmental benefits achieved through indirection selection for performance appear modest compared to financial gains, additional modelling showed that expanding the national breeding programme, embracing genomics and assessing phenotypes more closely aligned to methane production would generate reductions in emissions intensity of 180% (sheep) and 74% (beef) compared to the status quo.

The cost benefit to the industry of investing in this genetic work ranged from 8:1–18:1 in sheep and 4:1-6:1 in beef cattle.

The UK sheep and beef industries currently underutilize the genetic resources that are available to them when selecting breeding stock. However, for the most part, environmental breeding objectives are closely aligned to desirable performance characteristics in our livestock and thus the use of improved genetics to provide environmental benefits should be regarded as a win-win.

 

Take home message:

• Use EBVs to source rams/bulls which will improve your herd/flock efficiency, reducing environmental impact whilst also increasing profits.

 

Reference:

• Optimising Mature Weight for Farm Efficiency And Profitability (P61110077) produced by AbacusBio Limited (2019)
• A Vision for Improving the UK Sheep and Beef Sectors Through Breeding Over the Next 10 Years produced by AbacusBio Limited (2022).