General welfare
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Welfare implications of tail docking and castration in sheep

E.Mainau, D.Temple, P.Llonch, X.Manteca

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Tail docking and male castration are routine practices in sheep and are carried out in several countries without anaesthesia and/or analgesia. As these procedures cause both acute and chronic pain, the rationale for doing them and the effectiveness of pain mitigation strategies should be considered.

Rationale and justification of the practices

Prevention of blowfly strike is the primary reason given for tail docking in sheep, but the scientific evidence to support this ratio­nale is sparse.

During a blowfly strike, eggs are deposited into the tissue of the animal (cutaneous myiasis). Flies are mainly attracted to the breech of the sheep, probably because this area is continually warm and moist. Fly strike may be a major welfare problem when it occurs. Additionally, it leads to reduced wool quality and quantity and re­duced ewe fertility. In severe outbreaks of fly strike, mortality rate can be as high as 10% of the flock. The percentage of the sheep population affected by fly strike varies by region, ranging from 0.3 to 18%.

Tail docking is thought to reduce the risk of fly strike by pre­venting build-up of faecal material (called “dags”) on the tail, breech and hindquarters. While some studies show that daggy sheep are more likely to be struck, the relationship between tail docking and dags is unclear. Indeed, conflicting results have been obtained when comparing the incidence of fly strike in docked and undoc­ked sheep.

 Overall, the justification for tail docking in sheep varies on a flock by flock basis depending on the geographical region, the breed of the animal and other management practices. Routine tail docking is unlikely to benefit sheep that do not have wool (hair breeds and some dairy sheep) or that are kept regions with low in­cidence of blowfly strike. In some cases, tail docking is done because of tradition and this is not acceptable on animal welfare grounds. When the tail is docked, it is recommended to leave a minimum of three palpable coccygeal vertebrae in the tail stump (covering at least the anal region and vulva of the animals).

Castration prevents the aversive flavour which is characteristic of the meat of some intact male lambs once they reach puberty. Other benefits of castration include preventing undesired pregnan­cies and reducing aggressive behaviour.

 

Description of the procedures

The method of castration and tail docking varies between regions and farming systems. However, the application of rubber rings within the first week of life seems to be the most frequently per­formed procedure.

Tail docking by surgery involves severing the tail using a knife or scalpel. The docking iron is a similar approach to the surgical approach, except that the wound is cauterized. The rubber ring re­duces blood flow to the distal portion of the tail, which eventually becomes necrotic and sloughs off. In some cases, a clamp is applied for 10 s next to the rubber ring as a method to crush and thereby destroy the underlying nerves.

Surgical castration is either performed by incision of the scro­tum and cutting or tearing the spermatic cords, either by full scrotal ablation. Castration may be also done by using a rubber ring, a latex band and/or a clamp (Burdizzo). All techniques lead to testicular necrosis. Alternatively, short scrotum castration consists of pushing the testes up into the abdominal cavity by applying a rubber ring around the distal scrotum. The higher temperature in the abdomen affects testicular function and induces infertility.

 

Pain caused by castration and tail docking

There is both behavioural and physiological evidence that tail doc­king and castration are stressful and painful procedures for sheep (see FAWEC Fact Sheet nº17). Acute pain induced by these proce­dures lasts several hours and is followed by chronic pain which can last more than 48h.

 

Which method is less painful?

All tail docking methods result in acute pain. Lambs surgically tail docked show elevated cortisol levels and abnormal standing and walking after the procedure. Cauterization is known to relieve pain in lambs that are surgically tail docked.

Lambs tail docked with rubber rings show elevated cortisol levels and spent more time in abnormal postures and active behaviours associated with ischaemic pain compared with control lambs. Application of a clamp associa­ted with ring tail docking reduces pain.                     

  Tail docking with rubber ring  

Numerous studies show that surgical castration is more pain­ful than the other methods. Lambs surgically castrated show more pain-related behaviours and higher cortisol levels than lambs castra­ted by other methods. Levels of acute phase proteins are also higher in surgically castrated animals. Lambs castrated by rubber ring show more pain-related behaviours and have higher cortisol levels than lambs castrated using a clamp.

 

Is there an age effect?

When castration and tail docking are carried out at 5, 21 and 42 days of age, behavioural responses have been similar regardless of ages, suggesting that young animals have presumably the same pain perception than older animals. Pain in young lambs interfere with colostrum intake and bonding with the ewe. In addition, recent studies show that lambs castrated at a very young age are more sensitive to subsequent pain than lambs castrated at an older age. There is some evidence that older lambs show a greater chronic in­flammatory response to castration than very young lambs (less than 2 days old). However, this might have been related to the amount of scrotal tissue removed rather than being a direct effect of lamb age on pain response.

 

Minimizing pain

Both behavioural and physiological responses indicative of pain as­sociated to tail docking and castration are reduced when pain relief is provided.

Local anaesthetics reduce acute pain during castration and tail docking. For tail docking, the injection of a local anaesthetic sub­cutaneously into the tail immediately after the application of the ring or several minutes before the surgical or clamp procedure, re­duces pain. For castration, injection of lidocaine into the scrotal neck blocks the afferent fibres of the spermatic nerve, and reduces pain during surgical, rubber ring, clamp and combined ring and clamp castration. Topical anaesthetics containing lidocaine and bu­pivacaine have been shown to significantly decrease pain associated to surgical castration.

Non-Steroidal Anti-inflammatory Drugs (NSAIDs) provide effective post-operative analgesia. Following castration and tail doc­king, lambs receiving NSAIDs show less pain-related behaviours compared with lambs receiving no pain relief, and the magnitude of the effect can be very substantial. For example, meloxicam has been shown to cause a 7-fold reduction in behaviours indicative of pain after castration and tail docking, and the effect was still significant at 24 hours, when the study was terminated. Important considerations for the use of analgesic drugs in sheep include the ease of applica­tion and the duration of their effect.

 

"Tail docking and castration cause pain regardless of the method used and the age of the animals”

 
 

Summary

The need to carry out painful husbandry practices such as castra­tion and tail docking should be assessed on a case-by-case basis. Age has very little effect (if any) on the pain caused by castration and tail docking. Based on measurements of cortisol, surgical tail docking seems to cause more distress than other methods. Both local anaesthetics and NSAIDs are useful to reduce pain caused by castration and tail docking.


 

References 

  • Rault J-L, Lay Jr DC, Marchant-Forde JN, 2011. Castration induced pain in pigs and other livestock. Applied Animal Beha­viour Science 135: 214-225.

  • Sutherland MA, Tucker CB, 2011. The long and short of it: A review of tail docking in farm animals. Applied Animal Beha­viour Science 135: 179-191.

 

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Farm Animal Welfare Education Centre
Dr. Xavier Manteca Vilanova
Dra. Eva Mainau Brunsó
Dra. Déborah Temple

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email: info@fawec.org

 

Farm Animal Welfare Education Centre
Departament de Ciència Animal i dels Aliments, VO-135 Edifici V - Campus UAB -
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