The second instalment of the Teagasc beef conference on Wednesday evening included a presentation on the implications of slaughter age of beef cattle on greenhouse gas (GHG) emissions from beef enterprise leader at Teagasc Grange Paul Crosson.
From the outset, Crosson outlined the positive story Irish beef had to tell with one on the lowest beef carbon footprints in Europe and indeed across the world at 20kg CO2 e/kg beef.
This figure comes from the carbon emissions of both the cow (to produce the calf) and then that animal throughout its production system.
However, there are clear areas that can be improved within the system to decrease overall GHG emissions further in the future.
Such things as reducing the age at first calving to 24 months, increasing the number of calves weaned per 100 cows to the bull and indeed selectively breeding for lower methane-producing animals.
All of which work hand in hand with productive livestock systems and make both economic and environmental sense.
Reduced slaughter age
Reducing slaughter age also has the potential to reduce the overall GHG emissions from beef systems.
Crosson outlined that a typical suckler beef system in Ireland, where the average age at slaughter is 28 months old, has a total GHG emissions (kg CO2 e/head) figure of just over 7t.
If we were to reduce slaughter age by one month, it would potentially reduce the total GHG emissions by around 250kg/head – a reduction of somewhere around 3.6% per animal.
However, research carried out at Teagasc Grange, looking at GHG emissions from various production systems, has shown that if a reduced slaughter age comes at the expense of carcase weight or due to increased levels of concentrate input, there are no benefits in terms of emissions per kilo of beef.
In fact, when comparing a 24-month system where cattle are slaughtered out of the shed in spring on a diet of silage plus concentrate, versus a 28-month system off grass where no concentrate is fed either during the winter or finishing period, the GHG emissions/kg beef are lower in the 28-month system.
This is due to the higher GHG emissions associated with concentrate feed compared with grass.
In conclusion, Crosson emphasised the need for the Irish beef industry, with a strong reputation of producing beef from pasture-based systems, to be careful how we approach reducing slaughter age.
The system profiled that had the lowest GHG emissions/kg beef was where animals were slaughtered off grass at the end of the second grazing season from a grass-only diet.
However, there were issues over hitting carcase specification in this system with late-maturing breed types, in terms of carcase fat score.