Greenhouse gas (GHG) emissions from sheep production vary greatly depending on farm type and system.
Lower emissions are often associated with lowland systems – largely because more kilos of meat are produced from each hectare or breeding ewe.
Changes to diets, animal management and husbandry, as well as improvements in genetics, all have potential to reduce GHGs. But which have the greatest potential, and how do their costs compare?
See also: 20 ways dairy producers can tackle net zero
Research into a range of mitigation strategies was carried out by a group of scientists for the Centre of Innovation and Excellence in Livestock (Ciel), headed by Professor Elizabeth Magowan from the Agri-Food and Biosciences Institute (see table below).
The research shows, for example, finishing lambs at a younger age would be a low-cost way of cutting both methane and nitrous oxide emissions.
By contrast, feeding a higher starch content diet could be more costly, and more difficult to implement, but could have a significant impact on carbon footprint by reducing methane emissions.
Mitigation strategies to reduce GHG emissions in sheep |
|||||||
|
Strategy |
Cost |
Ease of implementation |
State of readiness to implement |
Potential GHG mitigating effect |
Impact on carbon footprint |
Other impacts |
Accounted for in the National Inventory |
|
Feed |
|
||||||
|
Higher starch content diet |
Medium |
Medium |
Now |
Methane reductions |
Medium |
|
Yes |
|
Increasing dietary oil and fat content, dietary inclusion of oilseeds |
Medium |
Medium |
Now |
Methane reductions |
Medium |
|
Yes |
|
Low crude protein diets |
Low |
Medium |
Now |
Methane and nitrous oxide reductions |
Medium |
Ammonia reductions |
Yes |
|
Feeding tannin- and saponin-rich forage |
Medium |
Medium |
Now |
Methane reductions |
Medium |
|
No |
|
Feeding methane inhibitors |
|
|
|
|
|
|
|
|
3-NOP |
Unknown |
Medium |
Later |
Methane reductions |
High |
|
No |
|
Nitrate* |
Low |
Medium |
Later |
Methane reductions |
Medium |
|
No |
|
Active compounds from seaweeds |
Unknown |
Medium |
Later |
Methane reductions |
High |
|
No |
|
Specialised feed ingredients/additives |
Low |
Medium |
Now |
Methane reductions |
Low |
|
No |
|
Forage |
|
||||||
|
Grass-legume mixtures, multi-species swards |
Low |
Medium |
Now |
Methane and nitrous oxide reductions |
Medium |
Good for biodiversity |
Yes |
|
Improved forage quality by early harvest, increasing grazing frequency, decreasing regrowth interval etc |
Low |
High |
Now |
Methane reductions |
Medium |
|
Yes |
|
Animal |
|
||||||
|
Genetic selection for inherently low enteric methane emissions |
Low |
Low |
Later |
Methane reductions |
Low |
|
Yes |
|
Genetic improvement in female productivity (fertility, lower mature weight, health, longevity and early lamb growth/survival) |
Low |
Low |
Now |
Methane and nitrous oxide reductions |
Low |
Ammonia reductions |
Yes |
|
Genetic improvement in terminal productivity traits (e.g., growth rate) |
Low |
Medium |
Now |
Methane and nitrous oxide reductions |
Low |
Ammonia reductions |
Yes |
|
Improved animal health |
Low |
Medium |
Now |
Methane and nitrous oxide reductions |
Medium |
Ammonia reductions |
Yes |
|
Finish lambs at a younger age |
Low |
Medium |
Now |
Methane and nitrous oxide reductions |
Medium |
Ammonia reductions |
Yes |
|
First mating of ewes as lambs rather than yearlings |
Low |
Medium |
Now |
Methane and nitrous oxide reductions |
Medium |
Ammonia reductions |
Yes |
|
Manure/fertiliser |
|
||||||
|
Nitrification and urease inhibitors |
Medium |
High |
Now |
Nitrous oxide reductions |
High |
Ammonia reductions |
Yes |
|
Source: Ciel. Notes: *Extreme care required during incorporation to diets due to animal health concerns. Impact on carbon footprint was assessed via a carbon calculator. The National Inventory and inventory accounting is used by the government to measure the carbon emissions and carbon capture at a sectoral and national level. Low ease of implementation means more difficult to implement. May require infrastructure or full system changes. |
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Expert view – Liz Genever
Independent beef and sheep consultant Liz Genever says there is a balance to be found between reducing emissions and maintaining productivity on sheep farms.
Below, she offers some practical tips on tackling net zero in lamb production.
Feed and forage
The challenge with strategies such as higher starch diets, increasing dietary oil and fat content and feeding methane inhibitors is that it involves some kind of confinement and buying in feed.
This conflicts with most of the advice for sheep farmers which is to try and maximise production from grass and forage.
This is largely to reduce the risks associated with buying in feed, such as price volatility.
However, in systems that rely on creep feeding, there is potential to make some tweaks to what is being fed.
Generally, barley and wheat and their associated co-products will supply high starch.
Feeding a low crude protein diet is quite difficult to do when a lot of production is reliant on grass and forage – which is inherently higher in protein levels.
A lot of feeding adjustments will be very much system-dependent.
Forage and grassland are a bigger area for intervention.
Rotational grazing on diverse swards has been shown to improve animal performance, which in turn reduces the methane associated with production.
To get the most from multispecies swards: ensure careful management of sward quality; increase the amount of clover to reduce reliance on nitrogen fertiliser; and incorporate herbs to build resilience into the sward under potential stress periods, such as changeable weather.
Genetics
As lovely as it would be to select low-emitting sheep, the relevant data is not yet available in the UK.
However, there has been a huge improvement in how terminal sire traits are recorded. Our challenge now is to get these genetics taken up by the commercial sector and the benefit seen on-farm.
The AHDB RamCompare project shows the benefits of performance-recording animals, in terms of growth rates, but it also shows how big the variation can be.
Genetics is one part of the solution, but it is also important to consider what kind of environment these genetics are being reared on.
Female efficiency should be a big focus for the industry now.
There are some examples of breeds that are doing this, such as Lleyns, which are Signet-recording the highest number of females of any breed in the UK.
This means there is more selection pressure on the females, and it is easier to find the ones that are doing the job and – just as importantly – the ones that are not.
Animal management
Achieving optimum growth rates will aid emissions reductions. Body condition scoring regularly is a way of keeping on top of this.
Mating as ewe lambs may be applicable under some systems, but if done badly, it can go very wrong.
Look at it on a year-by-year basis, assessing what grass cover is available and whether lambs are likely to hit good growth and weight targets, for example.
It is important to prioritise the lamb’s long-term fertility.
Lamb sector snapshot
The report by the Centre for Innovation Excellence in Livestock’s (Ciel), Net zero and livestock: How farmers can reduce emissions, provides a snapshot of the lamb sector:
- UK lamb and mutton production was valued at £1.3bn in 2020 – accounting for 5% of the UK’s gross agricultural output
- There are lower emissions in lowland systems than in upland systems in the UK. This is due to higher output (kilo of meat produced) a hectare of land used and/or a breeding ewe in lowland systems
- In a scientific study, the average GHG emissions intensity of lamb produced by lowland systems measured 11kg carbon dioxide equivalent (CO2e)/kg of liveweight and by upland and hill systems 13-18kg CO2e/kg of liveweight
This series takes as its starting point the Centre for Innovation Excellence in Livestock’s recent report, Net zero and livestock: How farmers can reduce emissions
