E.Mainau, D.Temple, P.Llonch, X.Manteca
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Tail docking and castration of males are routine practices in sheep that are performed in several countries without anesthesia and/or analgesia. Because these procedures cause both acute and chronic pain, both the alleged reasons for performing them and the efficacy of pain control strategies should be considered.
Rationale and justification for these practices
The main reason for tail docking in sheep is the prevention of cutaneous myiasis, caused mainly by flies of the genus Lucilia. However, scientific evidence on the efficacy of tail docking in the prevention of myiasis is scarce.
The flies responsible for cutaneous myiasis lay eggs mainly in the hindquarters of sheep, probably because this area is continuously warm and moist. Cutaneous myiasis can be a major welfare problem and also has negative effects on wool quality and quantity, as well as on the fertility of the sheep. In severe episodes, the mortality rate can be up to 10%. The percentage of the sheep population affected varies between 0.3 and 18% sdepending on the geographical region.
Tail amputation is believed to reduce the risk of cutaneous myiasis by preventing the accumulation of fecal material in the tail and hindquarters. While some studies show that the accumulation of dirt in these anatomical areas increases the risk of myiasis, the relationship between tail docking and dirt accumulation is unclear. In fact, conflicting results have been obtained when comparing the incidence of cutaneous myiasis in ewes with full tails and ewes that had had their tails docked.
In general, the rationale for tail docking in sheep varies with geographic region, breed of animal, and other management practices. Routine tail docking is unlikely to benefit sheep that are woolless or live in regions with low incidence of cutaneous myiasis. In some cases, tail docking is done as a matter of tradition and this is not acceptable in terms of animal welfare. When the tail is amputated, it is recommended that a minimum of three palpable coccygeal vertebrae be left in the tail stump so that the tail covers at least the anal region and vulva of the animals.
Castration avoids the unpleasant taste that is characteristic of the meat of some entire male lambs once they reach puberty. Control of reproduction and aggressive behavior are other reasons for castration.
Description of procedures
The method of castration and tail docking varies among regions and production systems. However, application of rubber rings during the first week of life appears to be the most common procedure.
Surgical amputation of the tail by surgery involves cutting off the tail using a knife or scalpel. The amputation iron is similar to the surgical method, except that the wound is cauterized. The rubber ring reduces blood flow to the distal portion of the tail, which eventually undergoes necrosis and detaches. In some cases, an emasculator is applied for 10 s to the side of the ring to destroy the nerve pathways.
Castration can be performed by cutting the spermatic cords (surgical castration) or by using a rubber ring, a latex band or an emasculator (Burdizzo). An alternative technique is called “short scrotum castration”, which consists of pushing the testicles into the abdominal cavity by applying a rubber ring around the distal scrotum, so that the higher temperature in the abdominal cavity adversely affects testicular function and causes infertility.
Pain caused by castration and tail docking
There is evidence based on both animal behavior and physiological parameters that demonstrate beyond doubt that tail docking and castration are stressful and painful procedures (see FAWEC Fact Sheet No. 17). The 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 cause acute pain. Lambs that have their tails surgically amputated show elevated plasma cortisol concentration and abnormal standing and walking post-procedure. Cauterization is known to relieve pain in lambs that have their tails surgically docked.
Lambs whose tails are docked with a rubber ring have elevated plasma cortisol concentration, spend more time in abnormal postures, and exhibit more active behaviors associated with ischemic pain compared to control lambs. The application of an emasculator associated with rubber ring amputation reduces pain.
Numerous studies show that surgical castration is more painful than other methods. Surgically castrated lambs show more pain-related behaviors and higher plasma cortisol concentration than lambs castrated by other methods. The plasma concentration of acute phase proteins is also higher in surgically castrated animals. Lambs castrated by rubber ring show more pain-related behaviors and have a higher plasma cortisol concentration than lambs castrated using an emasculator.
is there an age effect?
When castration and tail docking are performed at 5, 21 and 42 days of age, behavioral responses are similar regardless of age, suggesting that young animals presumably have the same perception of pain as older animals. Pain in young lambs interferes with colostrum intake and bonding with the dam. 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 inflammatory response to castration than very young lambs (less than 2 days old). However, this could be related to the amount of scrotal tissue removed rather than a direct effect of lamb age on pain sensitivity.
Minimizing pain
Both behavioral and physiological responses indicative of pain associated with tail docking and castration are reduced when local anesthetics and/or nonsteroidal anti-inflammatory drugs (NSAIDs) are administered.
Local anesthetics reduce acute pain during castration and tail docking. In the case of tail docking, injection of a local anesthetic subcutaneously immediately after ring application or several minutes before tail docking surgically or with emasculator reduces pain. In the case of castration, injection of lidocaine into the scrotal neck blocks the afferent fibers of the spermatic nerve and reduces pain during castration, whether castration is performed surgically, with rubber ring, with emasculator or by a combination of ring and emasculator. Topical anesthetics containing lidocaine and bupivacaine have been shown to significantly decrease pain associated with surgical castration.
Nonsteroidal anti-inflammatory drugs provide effective postoperative analgesia. After castration and tail docking, lambs receiving NSAIDs exhibit fewer pain-related behaviors compared with lambs not receiving NSAIDs, and the magnitude of the effect can be quite substantial. For example, meloxicam has been shown to cause up to a 7-fold reduction in pain-indicative behaviors after castration and tail docking, and the effect remains significant until at least 24 hours after the procedure, when the study was terminated. Ease of application and duration of analgesic effect are important considerations when using NSAIDs in sheep.
“Tail docking and castration cause pain regardless of the method used and the age of the animals.”
Summary
| The need to perform painful management practices, such as castration and tail docking, must be evaluated on a case-by-case basis. Age has little (if any) effect on the pain caused by castration and tail docking. According to studies that have measured changes in plasma cortisol concentration, surgical tail docking is more painful than the other methods. Both local anesthetics and NSAIDs are useful in reducing the 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.
