利用者:H-JAM/下書き

断尾（だんび）とは、動物の尾をヒトの手によって全部または一部切断する行為である。

豚

米国アイオワ州の養豚処理業者によって行われた子豚の断尾（2011年撮影）。麻酔をせずに断尾された子豚は、激しい痛みを感じ、多大なトラウマを抱えることとなる。

豚の断尾は通常、生後2–4日の時点で麻酔なしで行われる。豚の尾には先端まで末梢神経が伸びているため、尾を切断された子豚は激しい痛みを感じ、多大なトラウマを抱える。

家畜の豚の多くは、狭い空間で高密度多頭飼育されている（集約畜産）。そのような飼育環境で多大なストレスを抱えた豚は、別の豚の尾をかじることがある。これを防ぐために行われているのが断尾である。ただし、適切なスペースを確保し、一定量の水と藁（わら）を提供するなど、適切な環境が保たれている場合には、豚は他の豚の尾をかじることはないと報告されている。

なお、ブラジルやタイ、リトアニア、スウェーデン、フィンランド、アイスランドなどでは、動物福祉（アニマル・ウェルフェア）上の理由から豚の断尾は一切行われていない。また、EU諸国やカナダにおいては、麻酔なしで断尾を日常的に行うことは違法とされている。フランスでは、日常的に豚の尾を切断していた養豚業者に対して、動物虐待の罪で有罪判決が下された事例もある。

しかし、米国や日本では、麻酔なしの断尾という慣行がいまだに広く残っている。日本養豚協会の調査（2016年）によれば、日本では91.3%の農家が麻酔を使わずに断尾している。

羊

断尾される子羊（1920年撮影）

硬いゴムリングを尾に付けられている子羊。尾の血行を止めることで尾は数週間かけて壊死（えし）し、最終的に脱落する

断尾されていない羊。羊は本来、この写真にあるように長い尾を持つ。しかし、多くの場で断尾が行われているため、羊の尾は本来短いと勘違いする者も少なくない。

現在、多くの品種の羊が断尾されているが、これは糞が尾に付着することでハエが集（たか）るのを防ぐためとされる。なお、同じ理由から、臀部の皮膚を切り取られたり皮を剥がれたりすることもある（ミュールシング）。

While tail docking is an effective preventive method in some cases, if it is not carried out correctly it may result in other problems such as ill thrift or rectal prolapse. In lambs, tail docking at the distal end of the caudal folds tends to minimize docking effects on incidence of rectal prolapse. Docking at that length has been recommended by the American Veterinary Medical Association. In the UK the law states that for sheep docked tails should at a minimum cover the anus in male lambs, and the vulva in female lambs. These minimum lengths are also recommended in Canada.

Depending on the animal and the culture, docking may be done by cutting (knife or other blade), searing (gas or electrically heated searing iron), or constriction methods, i.e. rubber ring elastration. The Canadian Veterinary Medical Association indicates that pain, stress, recovery time and complications associated with docking of livestock will be minimized by docking when animals are under one week of age. However, docking of lambs within 24 hours of birth is not recommended, as it may interfere with ingestion of colostrum and/or formation of the maternal bond. In the UK the law requires that docking on sheep using constriction methods must be performed within the first week of the animal's life. The UK Farm Animal Welfare Council has noted that this limitation can be problematic in management of hill flocks where normal practice is to handle lambs as little as possible during the first week "to avoid mis-mothering, mis-adventure and injury."

犬

Dog with partially docked tail sniffing for truffles

→詳細は「Docking (dog)」を参照

As with other domesticated animals, there is a long history of docking the tails of dogs. It is understood to date at least to Ancient Greece. The most popular reason for docking dog breeds is to prevent injury to working dogs. In hunting dogs, the tail is docked to prevent it from getting cut up as the dog wags its tail in the brush. This is contested by a wide range of groups and is sometimes considered a form of animal cruelty. This has led to the practice being outlawed and made illegal throughout many countries, in some of which dogs are no longer bred for work, or used as working animals.

For example, in eighteenth-century England, tail docking became conventional following the implementation of a tax levied against non-working dogs (a docked tail designated status as a working dog). The push for industry regulation, characteristic of the twentieth-century UK, culminated in the passage of Veterinary Surgeons Act 1966. Therein, tail docking was explicitly declared to be legal and exempt from regulation when performed by persons of or over the age of eighteen—notably before the dog opens its eyes in infancy. Withal, a 1991 amendment to the act by Parliament enacted a prohibition of the docking of dogs' tails by lay persons from 1 July 1993 onward—thus abridging the practice to veterinary surgeons only. The passage of this amendment resulted in a response from the Council of the Royal College of Veterinary Surgeons, when in November 1992 the group ruled docking to be unethical "unless for therapeutic or acceptable prophylactic reasons". Critics highlighted that the imperatives, posited by the Royal College, for prophylactic docking were so strict that they made the routine docking of puppies by veterinary surgeons extremely difficult to near impossible. Veterinarians who presently exercise tail docking risk disciplinary action, and can be removed from the professional register. Those found guilty of unlawful docking would face a fine of up to £20,000, up to 51 weeks imprisonment or both. They can only dock the tail of "working" dogs (in some specific cases) – e.g. hunting dogs that work in areas thick in brambles and heavy vegetation where the dog's tail can get caught and cause injury to the dog. Docking was banned in England and Wales by the Animal Welfare Act 2006 and in Scotland by the Animal Health and Welfare (Scotland) Act 2006.

In 1987 the European Convention for the Protection of Pet Animals, established by Council of Europe, prohibited docking for non-medical reasons, though signatory countries are free to opt out of this provision, and almost half of them have done so. Norway completely banned the practice in 1987. Other countries where docking is banned include Australia and the United Kingdom.

馬

→詳細は「Tail (horse)」を参照

Docked and banged tail on a polo pony, photographed between 1910 and 1915

Originally, most docking was done for practical purposes. For example, a draft horse used for hauling large loads might have had its tail docked to prevent it from becoming entangled in tow ropes, farm machinery, or harness; without docking, it could be dangerous to the horse, painful if the tail were tangled, and inconvenient to the owner to tie up the horse's tail for every use.

In modern use, the term usually does not refer to tail amputation as it does with some dog breeds. However, historically, docking was performed on some horses, often as foals. The practice has been banned in some nations, but is still seen on some show and working draft horses in some places, and is practiced at some PMU operations.

In modern times, the term "docked" or "docking" in reference to the tail of a horse generally refers to the practice of cutting the hair of the tail skirt very short, just past the end of the natural dock of the tail. In particular, the tail is often cut short to keep it from being tangled in a harness.

牛

Tail docking of dairy cows is prevalent in some regions. Some anecdotal reports have suggested that such docking may reduce SCC (somatic cell counts in milk) and occurrence of mastitis. However, a study examining such issues found no significant effect of docking on SCC or mastitis frequency or on four measures of cow cleanliness. Although it has been suggested that leptospirosis among dairy farm workers might be reduced by docking cows' tails, a study found that milkers' leptospiral titers were not related to tail docking. The American Veterinary Medical Association opposes "routine tail docking of cattle." Similarly, the Canadian Veterinary Medical Association opposes docking tails of dairy cattle.

Cattle on large Australian cattle stations often have the tail brush (not the dock) cut shorter (banged) before their release; this "bang-tail muster" indicates those having been counted, treated, their current pregnancy status determined, etc.

Tail docking in the dairy industry is prohibited in Denmark, Germany, Scotland, Sweden, the United Kingdom, and some Australian states, as well as California, Ohio, and Rhode Island. Several large organizations within the dairy industry are against tail docking because of the lack of scientific evidence supporting claims benefiting the practice. Scientific studies have demonstrated that there are numerous animal welfare issues with this practice (such as distress, pain, increased activity in pain receptors in the tail stump, abnormal growths of nerve fibers, sensitivity to heat and cold, and clostridial diseases). Fortunately, there is an effective and humane alternative to tail docking, which is switch trimming.

外部リンク

• ウィキメディア・コモンズには、断尾に関するカテゴリがあります。