Teagasc figures show that bull beef systems can reduce greenhouse gas (GHG) emissions by as much as 32% compared with a typical 24-month steer system.

The results are based on a number of dairy beef system studies that were carried out at Teagasc’s Johnstown Castle research centre in Co Wexford.

Production data from these systems was then modelled using the beef systems greenhouse gas emissions model to evaluate both direct and indirect GHG emissions of each system.

The animals used were all spring-born Holstein Friesians bought in as calves at around a month old and therefore, the entire production system, from arrival to farm through to slaughter, can be accounted for.


Four of the systems compared were:

  • A 24-month steer production system that saw bullocks slaughtered out of the shed on a diet of grass silage and 5kg/day of concentrate.
  • A 21-month steer system finished off grass with 5kg/day of concentrate fed for the final 100 days.
  • A 19-month bull system finished off grass with 5kg/day of concentrate fed for the final 100 days.
  • A 19-month bull system finished indoors on an ad-lib concentrate diet for the final 100 days.
  • Production, financial and GHG data can be seen in Table 1, which shows the extent of the differences between the varying systems.

    The difference in GHG emissions on a per kilo beef vary by as much as 32% when you compare an ad-lib bull system to a 24 month bullock system.

    Not only do the bull systems come out on top on a GHG basis, when net margin/head is calculated, the greatest margin is seen with the 19-month bull off grass.

    The overriding difference is the inherent production efficiencies that favour the bull systems. Both national and international data shows that bulls have a higher growth rate, as well as increased feed efficiency, compared to bullocks reared similarly.

    We only have to look back at the Irish Farmers Journal/Teagasc BETTER farm programme analysis, which year-on-year showed that the farms operating bull beef systems were the most profitable.

    Reducing GHG emissions

    Farmers are now being asked to reduce the age of slaughter of steers in order to reduce the overall GHG emissions from the system.

    During the recent virtual Teagasc Beef Conference, enterprise leader Paul Crosson presented figures showing the potential gains to be made in reducing slaughter age, provided carcase weight remained constant and the amount of concentrate fed was not increased in order to reach an earlier slaughter age.

    When you do the figures on it, every 30 days that we reduce the slaughter age of a steer has the potential to reduce the total GHG emissions by around 3.6%.

    However, if we look at a bull system, comparing a 19-month bull to a 24 month steer, each month reduction has the potential to reduce GHG emissions by 6.4%.

    In another study from Johnstown Castle, where under 16-month bulls were added to the equation, they ranked similarly to the 19-month bulls, as emissions savings from a younger slaughter age were offset by higher lifetime concentrate inputs.


    While these results are based on dairy beef animals, there is no reason to suspect any major differences in the results for suckler-bred animals.

    If we think back to pre-2013, about one in three young males from the suckler herd in Ireland were slaughtered as young bulls.

    Many farmers at the time were operating a bull system that saw a short second grazing period prior to a short ad-lib meal finishing period.

    This is a system that could deliver both on an economical and environmental standing. It also sat well with our grass-based production image. as concentrate only played a major role in the final 100 days of life.

    If we ask the industry why we are concentrated on steer beef rather than bull production, we are told that it is because the UK consumer wants steer beef, and with over 50% of our beef exports destined for the UK, this of course makes sense at the moment.

    However, the day will come when every package of meat on a supermarket shelf will have its GHG emissions/kg of product printed on the label.

    If two steaks are sitting side by side on a UK supermarket shelf, one an Irish steer slaughtered at 24 months and the other a high concentrate-fed French bull slaughtered under at 16-months with a lower GHG emissions figure, is our grass-fed beef image going to be enough to make the consumer pick up the Irish beef?