In the case of domestic pigs, where commercially raised animals are kept in close quarters, tail docking is performed to prevent injury or to prevent animals from chewing or biting each others' tails.
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 rectal prolapse.
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 (rubber rings or other tourniquets).
As with docking of dogs, it has been identified that this practice contributes to masking underlying shortcoming of a breed, which - if docking were not the general practice - would be countered through selective breeding of animals where the tail does not lead to medical problems.
The most popular reason for docking dog breeds is to prevent injury to working dogs. For instance, it has been stated that a vermin's bite to the working dog's flop ears can lead to a systemic infection, a serious medical problem that wouldn't occur were there no flop ears to be bitten.
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 often considered a form of animal cruelty and torture. 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 United Kingdom tail docking was originally undertaken largely by dog breeders. However, in 1991, the UK government amended the Veterinary Surgeons Act, prohibiting the docking of dog's tails by lay persons from 1 July 1993. Only veterinary surgeons were, by law, allowed to dock.
However, following the passage of the law, the Council of the Royal College of Veterinary Surgeons in November 1992, ruled docking to be unethical, "unless for therapeutic or acceptable prophylactic reasons". The requirement in which the Royal College considers prophylactic docking to be acceptable are so strict as to make the routine docking of puppies by veterinary surgeons extremely difficult. Vets who continue to dock 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.
In 1987 European Convention for the Protection of Pet Animals, established by Council of Europe has prohibited docking.
Also, Norway completely banned the practice in 1987.
Other countries where docking is banned: Australia, Austria, Belgium, Brazil, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Scotland, Slovakia, South Africa, Sweden, Switzerland, Virgin Island, Wales.