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Non-approved lamb castration methods
Information about lamb castration methods that are not used in England.
Aside from the five approved lamb castration methods described elsewhere, there are several other methods that are not approved for use in England:
- Immunocastration
- Chemical/hormonal castration
- Castration with use of anaesthetic simultaneously
- Other crush methods
There is little evidence about the impact of these practices on animal welfare, productivity, profitability and/or environmental sustainability. And, as they are not approved for use in England, we have not included comments about the legislation or farm assurance implications.
Immunocastration
Immunocastration is a non-surgical, painless method of castration that uses a protein injection (vaccine) to reduce reproductive hormones in animals. Two injections are needed: the primary dose and a booster.
Rams need gonadotrophin-releasing hormone (GnRH) to reach sexual maturity. The vaccine prevents GnRH from being released, making ram lambs infertile.
Castration via this method is reversible and the duration of infertility will depend on the interval between the primary and booster vaccination.
In the UK, immunocastration is licensed for pigs and has also been used on cattle; it cannot, however, be used on sheep.
International trials have highlighted the potential for immunocastration to improve the welfare, performance and meat quality of ram lambs.
Immunocastration provides similar fertility control and behavioural management to other castration methods but with productivity levels more akin to entire males.
In countries where immunocastration is permitted, the vaccine can be safely used on lambs from six weeks of age. There is a risk that should the procedure fail, alternative castration methods may be limited due to the age of the animal.
Potential advantages over traditional castration methods:
- Easier management
- Less labour
- Improved welfare, e.g. reduced injuries
- Flexibility in timing
The flexibility would lend itself to being used across a range of systems, including those that do not routinely handle young lambs. It could also enable you to make the most of the improved growth rates of entire lambs until reaching sexual maturity.
Chemical castration
Chemical castration involves injecting chemicals into the testes to reduce testosterone production.
Examples of the chemicals used on other species include lactic acid, zinc gluconate and zeranol implants. These cause inflammation and destroy testicular function, resulting in infertility. Serious side effects have been reported, including muscle wastage, anaemia and osteoporosis.
The lack of research and evidence for the use of chemical castration in sheep, and the reported side effects seen in other species, makes this method unlikely to be approved as a viable alternative to existing and/or emerging techniques.
Castration with anaesthetic (Numnuts®)
Numnuts® blocks the acute pain that follows castration of lambs with rubber rings. It consists of a rubber ring applicator, combined with an injector that dispenses local anaesthetic.
This method was developed in Australia and has been in use there since 2019; it was launched in New Zealand in 2021.
The method is not approved for use in England but was trialled by Scotland’s Rural College (SRUC) in a Defra-funded study in 2022. This study assessed the use of Numnuts® for castration and/or tail docking in lambs under seven days of age.
Preliminary results suggest that the Numnuts® technique was effective at eliminating the pain response associated with tail docking. However, there was no difference seen in pain-related behaviours in lambs castrated with Numnuts® or rubber ring castration.
Once the full results are available, they will be considered by Defra's Animal Welfare Committee (AWC; formerly FAWC).
Another study reported that Numnuts® appeared to be an effective way to deliver lignocaine (a local anaesthetic) and improve the welfare outcomes during the acute pain phase (5 and 20 minutes post application) but did not eliminate pain behaviours completely.
Further research found the effects of the local anaesthetic procaine to last longer than lidocaine, and bupivacaine was slower to take effect but appeared to provide longer-lasting relief. This study also noted that, in general, the effect of local anaesthetics in sheep is relatively short.
The Mutilations (Permitted Procedures) (England) Regulations (2007) currently prohibit the use of rubber rings, with or without anaesthetic, on animals older than seven days. If Numnuts® was to be recommended for use in England, this legislation would need to be updated.
Castration clip (ClipFitter)
This technique combines aspects of both rubber ring castration and the clamp technique.
It uses a Plastic clip that is clamped around the scrotum. The clip must be applied using a specialised tool, similar to a set of pliers.
The clip crushes the nerve and spermatic cords almost instantly, and the blood supply is subsequently cut off.
You apply the clip in a similar position to a rubber ring/clamp, and it remains on the animal until it is shed with the wasted scrotum from around three weeks after application. There is a range of applicators and clips to accommodate lambs of different sizes (5–20 kg).
The ClipFitter method was trialled by Scotland’s Rural College (SRUC) in 2022 and is authorised by the Scottish government for use in lambs up to three months of age without anaesthetic.
The technique has not yet been approved for England.
Preliminary findings suggest that the pain responses seen in young lambs (less than seven days old) castrated with ClipFitter are similar to uncastrated but handled lambs.
In older lambs (4–5 weeks old), ClipFitter caused an increased pain response shortly after application (first six minutes) compared with the clamp method plus pain relief, but it was similar thereafter.
Anecdotal comments suggest that the technique is easier to apply than a clamp.
It is unlikely that specialist training would be needed for those already familiar with the rubber ring method; however, it may take time to perfect the technique.