Farm Ireland

Sunday 18 March 2018

Winning the entire debate

Leaving lambs uncastrated is a win-win situation

Research shows that castrating lambs hits farmers' profits
Research shows that castrating lambs hits farmers' profits

Dr Tim Keady Animal and Grassland Research and Innovation Centre, Teagasc, Athenry

In mid-season prime lamb production, the objective is to achieve high levels of lamb performance in a cost-effective way. High levels of lamb performance result in early drafting, ensuring all lambs are sold by the end of the grazing season. In Ireland, 73pc of all lambs are sold between early May and late December.

As the lambing season progresses, an imminent question to face is whether or not to castrate male lambs.

There is a lot of evidence that finishing male animals entire increases their performance. However, there is a perception among industry commentators, producer groups, processors and marketers that leaving male lambs entire may have a negative impact on meat-eating quality. So what are the facts about the effects of castration on male lamb performance and subsequent meat quality?

Rearing males entire aids performance

In beef production, finishing male cattle entire (as bulls) and which are slaughtered at 24 months boosts carcass weight by 41kg, carcass conformation classifications (on a five-point scale) by 0.4 points and decreases carcass fat classification (on a five-point scale) by 0.7 points.

A study was completed at Athenry which evaluated the effects of castrating male lambs on subsequent performance and carcass characteristics. This study was undertaken using 157 all-male litters in mid-season prime lamb production systems.

In each of the all-male twins, one lamb was chosen at random and castrated shortly after birth, while its sibling was left uncastrated. The effects of castration on animal performance are in table 1.

Leaving the male lambs entire increased weaning weight by 1.8kg, reduced age at slaughter by 16 days and resulted in leaner carcasses.

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The reduced age at slaughter is similar to the response obtained from feeding 17kg concentrate/lamb prior to slaughter. The improvement in animal performance occurred for no extra cost or labour input. The financial gain, from leaving male lambs entire, under current market conditions is equivalent to €6/lamb. The reduced fat classification is of benefit to consumers as they have an aversion to fatness when buying meat.

Castration and meat quality

There is a perception that rearing male lambs entire may have a negative impact on meat-eating quality. Last year Dr Seamus Hanrahan, who was head of the Sheep Research Department at Athenry for 33 years, undertook a review of research published in the past 25 years which compared meat from castrated and entire male lambs.

Dr Hanrahan reviewed studies from France, the UK, New Zealand, Australia, Canada and Iceland, many of which are the main global producers of lamb.

There is no simple definition of meat quality, and assessment can involve objective measurements, such as chemical composition, instrumental measures of tenderness and/or subjective evaluation by trained taste panels or in-home by families.

Dr Hanrahan reviewed a British study in which meat from male lambs reared on pasture and slaughtered at 20 weeks was evaluated by a trained taste panel and by consumers in their own homes.

It was concluded that while the carcasses from the entire males were 1.2kg heavier, they had 23pc less fat. The trained panel failed to identify any difference in flavour, texture or acceptability. The consumers concluded that meat from the entire males had better aroma and resulted in a better eating experience (see table 2).


A subsequent British study evaluated leg joints from entire males slaughtered at seven- and-a-half months and from castrate males, unweaned, slaughtered at four months. The comparison would be expected to favour the young castrates. The joints were evaluated by consumers in Britain, France and Iceland. The results (in table 3) concluded that the leg joints from entire males had a higher score for all aspects of the evaluation and a higher overall acceptability score.

In the late 1990s, a two-year study addressed the concerns that French butchers had in relation to the declining quality of local lamb carcasses in late autumn/winter. The meat trade believed this decline was due to the failure of producers to castrate males. The study concluded that other factors were responsible for the late-season decline in quality.

A recent study undertaken in New Zealand evaluated meat from male lambs reared as castrates or entire and slaughtered from four to 24 months of age. The study showed there was no evidence of any effect on meat quality, whether male lambs were reared entire or as castrates, until 13 months of age.

Dr Hanrahan concluded that where lambs are reared on an all-grass diet and slaughtered by the end of the grazing season, leaving male lambs entire has no negative effect on meat quality, whether assessment is lab-based or consumer testing.


  • Leaving male lambs entire:
  • Increases lamb performance;
  • Reduces age at sale by 16 days;
  • Increases margin per male lamb by €6;
  • Produces leaner carcasses;
  • Does not impact on meat eating quality.
  • Leaving male lambs entire that are reared on an all-grass diet and slaughtered prior to the end of the grazing season has no negative effect on meat quality.
  • Consumers have an aversion to fat, therefore the leaner carcasses from entire males are of benefit when buying meat.

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