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Extensive research carried out by Teagasc and other research institutions shows that stocking rate and ewe prolificacy are major drivers in determining farm profitability.
However, there is little research on the effect that intensifying production has on greenhouse gas (GHG) emissions.
A recent study with this objective was undertaken based on data from the Teagasc research demonstration flocks between 2012 and 2015.
The findings are part of an extensive collection of the latest research undertaken across key sheep production performance parameters that will be presented at the Teagasc National Sheep Open Day, which takes place on Saturday 18 June from 10am to 4pm.
Study metrics
The trial treatments under investigation included three stocking rates – 10 ewes per ha (LS), 12 ewes per hectare (MS) and 14 ewes per ha (HS) - and two levels of prolificacy – medium with 1.5 lambs weaned per ewe (MP) and high with 1.8 lambs weaned per ewe (HP).
The increase in stocking rate across the systems was primarily supported through an increased fertiliser allocation as detailed in Table 1.
The Teagasc sheep lifetime assessment model (LCA) was used to calculate GHG emissions.
The production system accounted for emissions up to the point animals left the farm and includes farm inputs with fertiliser and concentrates the most significant in this regard.
Results
The findings show that when scaled to an area systems weaning 1.8 lambs per ewe emitted 9% to 12% more GHG emissions than systems weaning 1.5 lambs per ewe due to more animals in the system. This is detailed in Figure 1.
However, Figure 1 also demonstrates that when assessed on GHG emissions per kilo of carcase weight, increasing weaning rate from 1.5 lambs/ewe to 1.8 lambs/ewe reduced GHG emissions per kilo of carcase weight by 10% to 12%.
The reduction per kilo of carcase weight was due to a greater quantity of liveweight produced by high prolificacy ewes diluting ewe-related emissions.
Assessed
When assessed also on stocking rate, the findings showed that systems stocked at 14 ewes/ha emitted on average 43% more GHG emissions/ha than production systems stocked at 10 ewe/ha.
This increase was attributed to a greater number of animals in the system in addition to an increase in days to slaughter.
This indicates that emissions associated with increasing stocking rate surpassed the increase in productivity per ha where the higher stocking rate is underpinned by higher farm inputs, such as chemical fertiliser and concentrates.
The production of GHG emissions in livestock production is an area that is going to attract increased scrutiny given the lofty targets set to reduce GHG emissions by 2030.
As this article shows, there are numerous interactions at farm level that influence emissions.
Extensive research is currently being undertaken on numerous aspects of GHG emissions, including the role of clover and other companion forages in reducing chemical fertiliser requirements and optimising animal performance along with other mitigation measures including breeding sheep for lower emissions.
Wealth of information at Teagasc sheep open day
The Teagasc National Sheep Open Day takes place on Saturday 18 June from 10am to 4pm in the Animal and Grassland Research and Innovation Centre, Athenry, Co Galway (eircode H65 R718).
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