One of the most problematic animal welfare issues in modern pig production is tail biting. This abnormal behaviour compromises the well-being of the animals and can seriously impair animal health. Tail biting has a multifactorial origin and occurs mainly in fattening pigs. High stocking densities, poor environment and bad air quality are viewed as important factors. However, it is presumed that a plurality of internal and external motivators in intensive pig production can trigger this behaviour, which is not reported in wild boars (66).
Tail biting is an injurious, abnormal behaviour that occurs sporadically and unpredictably on factory farms. It involves progressive chewing of the tail from a mild scratch condition to one in which the entire tail is removed. Tail biting appears to be a result of redirected foraging behaviour in the barren environment. Once blood is drawn, the behaviour escalates.
Tail bitten pigs are also more likely to exhibit pleuritis (inflammation of the membranes surrounding the lungs) and lung abscesses (67).
Tail docking, or the amputation of the lower half of a pig’s tail, is carried out when there is a risk of pigs biting each other’s tails when they reach the ‘finishing’ stage. This risk is very high on a factory farm. A national survey by Exeter University in 1998 revealed that almost 100 per cent of indoor pig units tail dock (68).
In the wild, pigs do not bite each other’s tails. It is accepted by the pig industry that tail and ear biting are manifestations of the poor conditions of factory farms. Lean states that they are:
“Aberrant behaviours, suggesting management is at fault in being unable to satisfy the behavioural needs of pigs” (45).
Poor housing, early weaning, bad diet and a buildup of gases such as ammonia and carbon dioxide all cause tail biting. It is not the consequence of general aggression.
Several factors can increase the risk of tail biting, including health problems, delayed detection of a tail biting outbreak and lack of environmental enrichment.
In 1999, the Pig Improvement Company (PIC) Veterinary Manager stated:
“Aggressive behaviour is targeting at the head not the rear and tail biting is more likely to be a sign of frustration caused by insufficient nutrition or lack of feeding space” (69).
The tail is severed using clippers, a hot cauterising iron or a scalpel within seven days of birth, without anaesthesia or analgesia. The amount of tail removed can vary between operators from very little (tipping) to more than half. Tail docking is accompanied by handling stress and short term pain from tissue damage. It causes physiological and behavioural responses indicating acute stress when performed on six-day-old pigs. These include increased blood cortisol concentrations, reduced white blood cell count and increased sitting and scooting behaviour (70). Docked tails may develop neuromas, which are associated with increased sensitivity to pain (71). The extent of medium term and chronic pain is uncertain. A veterinarian does not need to be present if the amputation is carried out during the first week of the piglet’s life. Many animal welfare scientists believe tail docking is a painful procedure and should be avoided (72).
Found by Viva! investigators on a farm in 2015. Around 80 per cent of British piglets have their tails crudely severed using clippers, a hot cauterising iron or a scalpel © Viva!
Remarkably, the reason for the tail docking is the belief that once the lower part of the tail is cut off, the remainder is more sensitive and pigs quickly escape when others try to bite it. This implies that the cut tail is painful. If tails are cut, another problem arises. Lean states that docked piglets will often show “increased levels of neck and shoulder biting” (45).
Badly performed tail docking can lead to infections which may spread to the spinal cord causing spinal abscesses and deep pain. Arey (73) states:
“Wounds can become infected, resulting in abscessations of the hindquarters and... spinal column. Secondary infection may occur in the lungs, kidney, joints and other parts”.
Research reveals that tail biting (also bar biting in stall-housed sows in Europe, stone chewing in outdoor pigs, and high levels of aggression) are partly due to pigs being under nourished. Growing pigs may experience specific nutrient restriction when they are fed a single feed unsuitable for their age and weight.
Breeding pigs can be fed restricted rations to stop them putting on weight and to make them breed efficiently. In other words, they tail bite because they are hungry.
The pig’s response in all cases is to attempt to forage. In the wild, pigs would find food by digging, pushing, gnawing and rooting; however, many indoor farming environments have little or no potential to accommodate these behaviours.
This ‘compromises welfare’ because the pig turns his or her attention to tail biting, excessive drinking or vacuum chewing.