TAIL DOCKING AND WELFARE OF SHEEP
Tail docking of sheep has been opposed by some animal welfare advocates who perhaps fail to understand the welfare issues involved. By pointing to informed, professional opinion and scientific evidence, sheep producers may be able to help them understand the reasons for this practice and the associated issues.
Certainly some sheep appear not to need tail docking, for anatomical reasons (such as natural tail characteristics and/or having hair, rather than wool) or for other reasons (such as some Scottish Blackface flocks on British hill pastures, in contrast to lowland flocks).
But for most long-tailed wool sheep, there are commonly welfare benefits from tail docking. An American Veterinary Medical Association position statement (adopted in 2000) says: “Lambs' tails are docked for cleanliness and to minimize fly strike, but cosmetic, excessively short tail docking can lead to an increased incidence of rectal prolapses and is unacceptable for the welfare of the lamb. We recommend that lambs' tails be docked at the level of the distal end of the caudal tail fold.” This recommendation is in agreement with the U.S. Animal Health Association and the American Association of Small Ruminant Practitioners.
A Canadian Veterinary Medical Association position statement (March, 1996) recommends that where sheep docking and castration are necessary, they should be done within the first week of life: “Pain, stress, recovery time and complications will be minimized by performing these procedures on animals under one week of age.” It is commonly urged that these practices be deferred until the lamb has consumed colostrum and the ewe-lamb bond has been well established. For this reason, it is usual to wait until the lamb is at least 24 hours old.
The Canadian code of practice (CARC 1995) suggests that the following may be used for tail docking after the lamb has consumed colostrum and before 7 days of age: electric or gas heated docker; rubber ring; crush and cut device; rubber ring plus crushing device. Where docking and castration are done at the same time, Stafford and Mellor in the early 1990s suggested that one of the least stressful methods is use of rubber (elastrator) rings. (David Mellor is Professor and Director of the Animal Welfare Science and Bioethics Centre at Massey University, New Zealand.)
Because of risk of tetanus with several docking methods, it is often advised that (previously vaccinated) ewes should be vaccinated with a suitable tetanus toxoid vaccine about two weeks before lambing is expected. This raises the ewe’s antibody titre, providing abundant antibodies in colostrum, which should protect the lamb against tetanus throughout the first 12 weeks after birth, i.e. well beyond the high-risk period associated with early docking and castration. Commonly, the vaccine selected is “CDT” or “7-way” or “8-way”, to give simultaneous protection against various other clostridial diseases over a similar period. (See Kimberling, 1988.)
Evidence for the benefits of tail docking can be found in research by French et al. (1994), who studied 3172 lambs on 7 farms, including several sheep breeds and crosses. Fecal soiling was somewhat higher in undocked lambs, and blowfly strike was consistently higher in undocked lambs. They concluded that tail docking protected against blowfly strike, with little evidence of any detrimental effect on lamb mortality and production.
A study by Thomas et al. (2003), involving 1227 lambs at 6 locations, allocated each lamb randomly to one of three tail docking treatments: short (as close to the body as possible), medium (midway to the distal end of the caudal folds), and long (distal end of the caudal folds). Overall, rectal prolapses occurred in 7.8 % of short-docked lambs, 4.0 % of medium-docked lambs, and only 1.8 % of long-docked lambs. Some differences in prolapse frequency, perhaps associated with management or other differences, were seen at different locations.
The Canadian and United Kingdom codes of practice (CARC, 1995; MAFF [UK], 2000) recommend that tails should be left long enough to cover the anus in males and the vulva in females. The New Zealand code (Animal Welfare Advisory Committee, 1996) suggests that tails should be long enough to cover the vulva in females and a similar length in males. This recommendation is achieved by docking distal to the caudal folds.
How stressful is tail docking? The sheep producer commonly sees some behavioural indications of discomfort or pain. However, the significance of behavioural indicators may be difficult to estimate unless interpretations of behaviours have been developed in association with physiological measurements (Mellor et al. 2000). For sheep, Gregory (1998) has tabulated some observed peak concentrations of plasma cortisol, a hormone that is often a useful indicator of stress, including stress associated with pain. In :g per litre, these concentrations are shearing, 131; transport, 80; castration, 69; tail docking, 49; mustering, 48; restraint, 34. Clearly, docking tends to be stressful. But such data suggest that tail docking (if done with due regard to welfare) is not necessarily a highly stressful procedure, when compared with other common and necessary practices. Lambs not uncommonly show behavioural evidence of some stress and pain in the period soon after docking. However, most lambs exhibit normal behaviours again within about an hour. Elevated cortisol concentrations may persist for 3 or 4 hours (more or less, depending on the docking method used), but as the half-life of cortisol in blood is about 20 minutes (Gregory, 1998), elevated secretion of the hormone may have subsided for as much as an hour before the concentration in blood has fallen to near-baseline levels. Research on methods continues. Professor Vince Molony and Joyce Kent at the Royal (Dick) School of Veterinary Studies, Edinburgh, and the group at Massey University have been especially active in this area of research, seeking methods that will further minimize stress. However, the evidence suggests that even with some of the existing methods, the stress from tail docking can be moderate and not very prolonged.
In contrast, the stress and pain from a serious case of flystrike are very severe and can end with death of the sheep. A single female blowfly of some species can lay as many as 300 eggs, and a favoured place for deposition and hatching of these eggs is in moist, manure-soiled wool, or in a wound. Some instars of blowfly larvae possess structures that tear skin and flesh, attracting more flies. Larvae aggressively feed on flesh, using enzymes that break down the sheep’s tissues. Because larvae develop rapidly (about two and a half days from egg to the highly damaging third instar), welfare problems can already be acute by the time they become evident.
Some welfare advocates may be inclined to suggest that substantial prevention of flystrike by docking would be unnecessary if sheep were frequently inspected and then treated where flystrike is seen to be occurring. Although this may seem plausible to someone unfamiliar with sheep, it would, of course, be impractical with flock of even moderate size. Moreover, the significant and repeated stress associated with frequent mustering, restraint and close examination could be expected to impose substantially more serious welfare problems than are attributable to docking.
Canada has several species of blowflies (Calliphoridae) that can cause or exacerbate flystrike in sheep. Several Lucilia species are commonly called “greenbottle flies”, some Calliphora species are commonly called “bluebottle flies”, Phormia regina is the “black blowfly”, and Cochliomyia macellaria is the “secondary screwworm”. Descriptions of these can be found in various entomology and veterinary parasitology texts. According to Paula Menzie DVM MPVM (2004), species most commonly involved in fly strike in this country are Phormia regina, Protophormia terraenova and Lucilia sericata, but other blowfly species can also be attracted to an infested area. These include Lucilia illustris and Cochliomyia macellaria, among others.
The bottom line is that good docking technique can minimize some real welfare issues, and in many (but not all) situations, a failure to dock tails would seem indefensible from the standpoint of good husbandry and welfare.
Animal Welfare Advisory Committee. 1996. Code of recommendations and minimum standards for the welfare of sheep. Ministry of Agriculture, New Zealand.
CARC. 1995. Recommended code of practice for the care and handling of sheep. Canadian Agri-Food Research Council, Ottawa. 37 pp.
French, N. P. et al. 1994. Lamb tail docking: a controlled study of the effects of tail amputation on health and productivity. Vet. Rec. 134: 463-467.
Gregory, N. G. 1998. Animal welfare and meat science. CABI Publishing, Wallingford. 298 pp.
Kimberling, C. V. 1988. Jensen and Swift’s diseases of sheep. Third edition. Lea & Febiger, Philadelphia. 394 pp.
MAFF [UK]. 2000. Codes of recommendations for the welfare of livestock: sheep. Ministry of Agric. Fish. and Food, United Kingdom. 25 pp.
Mellor, D. J. et al. 2000. Quantifying some responses to pain as a stressor. In: Moberg, G. P and J. A. Mench (eds.) The biology of animal stress: basic principles and implications for animal welfare. pp. 171-198.
Menzie, Paula. 2004. Shepherds Journal. Vol. 12, No. 8, pp.8-9.
Thomas, D. L. et al. 2003. Length of docked tail and the incidence of rectal prolapse in lambs. J. Anim. Sci. 81: 2725-2732.