The Irish sheep sector does not feature prominently in discussions around greenhouse gas (GHG) emissions with the focus typically centred on the beef and dairy sectors.

It is not surprising that some in the sheep sector think that the 2030 target set for the Irish agricultural sector to reduce GHG emissions by 25% compared to 2018 levels will not affect the sheep sector.

While GHG emissions from sheep production are significantly lower relative to the two main livestock systems, Jonathan Herron of Teagasc says that this will not absolve the sheep sector from being expected to play its part in meeting law-binding targets.

Herron was speaking at the two Teagasc lowland sheep conferences held last week in Co Monaghan and Co Wexford.

He presented data that showed while breeding ewe numbers have fallen by over 35% from their peak level in the early 1990s, they have increased since 2010, albeit ever so slightly.

Cost-effective reduction

Teagasc research has championed the marginal abatement cost curve (MACC) as a tool for identifying blueprints for reducing GHG emissions.

For every measure that has been shown to reduce GHG emissions it looks at the cost benefit or cost negative associated with it, ie how much the measure will reduce GHG emissions but what the cost is of putting that in place.

There are three scenarios, cost benefit which will improve your profitability, cost neutral which will bring about no change in financial performance and cost-prohibitive measures that will cost you to reduce emissions.

“We want to improve the profitability and economic viability of these systems while also achieving the targets set to us by the Government.”

Key measures

Herron listed the following measures as being key for sheep systems:

  • Improved grassland management: “So you are looking at soil fertility, looking at your pH, your P and K indexes to ensure that any nutrients that you are spreading on your ground you are getting maximum utilisation.”
  • Companion forages: “Incorporating companion forages such as multispecies or white clover will help you to reduce your reliance on synthetic fertilisers.”
  • Grazing infrastructure: “If you put in a good rotational grazing system and ensure there is good-quality grass in front of your animals all the time you can potentially reduce your concentrate feeding.”
  • Fertiliser type: “Nitrous oxide (N2O) is a potent GHG, 300 times more potent than carbon dioxide, so it is very important that we try to target it. The vast majority of the fertiliser we spread in Ireland is in the form of CAN or compounds such as 18:6:12 and these fall under this fertiliser category where 1.4% of the nitrogen spread is going to be lost. If you go with protected urea, it is down at 0.4% so substantially lower. Using protected urea versus urea will also significantly reduce ammonia levels.”
  • Fertiliser quantity: “By incorporating clover in to your swards you reduce your reliance on farm inputs, which includes your fertiliser, while there is potential to maintain if not increase your productivity and reduce GHG emissions.”
  • Genetics: “We looked at the performance of animals in the one-star category and the five-star category. The difference is the weaning rate goes from 1.5 up to 1.7 lambs and the days to slaughter figure is 13 days lower. This translates to an €18 per ewe increase in profit and by selecting five-star versus one-star animals we were able to reduce GHG emissions per kilo of output by 7%.”
  • Stocking rate and prolificacy: “Three stocking rates, 10 ewes,12 and 14 ewes per hectare and two weaning rates, 1.5 lambs and 1.8 lambs, were looked at. As you increase your stocking rate and weaning rate your profit/ha is going to increase. When you look at GHGs and weaning rate, an extra 0.3 lambs per ewe, your carbon footprint reduces from 24.5 to 21 or 22. However, where stocking rate is increased through the use of more fertiliser, your GHG emissions will go up but, as I said, it is possible to increase stocking rate and reduce emissions through the use of white clover.”
  • Animal health: “When you look at animal health and you compare a healthy versus an unhealthy animal there is a lower food conversion efficiency, lower reproductive performance, higher mortality and increased culling rates. By addressing these and putting the right health plans in place you can reduce GHG emissions by allowing animals to reach their optimum performance.”

    • Case study

    Herron showed the benefits of adopting such improvements in efficiency on an average farm using lifecycle assessment models developed by Teagasc to calculate the environmental impact of agricultural systems in Ireland.

    This system not only takes account of emissions at farm level, it also takes account of emissions outside the farm gate in practices such as producing fertiliser, concentrates, electricity, fuel, etc.

    The model investigated all the elements above with efficiency improvements including the use of 100% protected urea, incorporation of clover to reduce fertiliser use by 20%, reducing concentrate feed from 103kg to 50kg, increasing weaning rate from 1.39 to 1.5 lambs per ewe joined and reducing mortality across the system from 7.9% to 5% on the average sheep system outlined below.

    Results

    The typical GHG intensity of a lowland system was calculated at 10.8kg CO2 equivalent/kilo of liveweight, significantly lower than the global average figure of 11.3kg CO2 equivalent/kg liveweight. Improving mortality and weaning rate reduced the GHG intensity (per kilo of output) by 2.2% and 4.9%, respectively, while total GHG emissions (per hectare) were unchanged due to more live lambs on the ground.

    Incorporation of clover reduced both GHG emissions and intensity by 2% and 2.4%, respectively, while protected urea reduced GHG emissions by 5% and GHG intensity by 2.4%.

    Reducing concentrate feeding built in a reduction in stocking rate due to increased forage intake and maintaining inputs such as fertiliser static in the model.

    It was responsible for reducing GHG emissions and intensity by 4.3% and 1.7%, respectively.

    The combined benefit of all these measures resulted in GHG emissions reducing by 9.7%, while the intensity of GHG emissions per kilo of output reduced from 10.8kg CO2 equivalent/kg liveweight to 9.6kg CO2 equivalent/kg liveweight.

    Herron concluded that the Irish sheep sector needs to adopt GHG emissions mitigation strategies available, not only to contribute to agriculture’s 2030 target, but also to improve efficiency at farm level and improve the marketability of Irish lamb.