Age affected: Weaners, growers / finishers.
Causes: Poor housing or ventilation; overcrowding; stress; dietary problems; irritating diseases.
Effects: Bleeding or damaged tails, paralysis or carcase condemnation from spinal abscesses.
Once tail biting has started, the damage leads to bleeding and excess movement of the tail due to irritation, attracting other pigs to the blood and causing further damage. Slaughterhouse surveys demonstrate that the sex of the pigs concerned affects tail biting and that it is more common in boars (4.6%) than in gilts (3.4%). Similarly, possession of a tail of normal length is more likely to result in tail biting (9.2%) than if tails are docked (3.1%).
Other causes are less well defined. Part of the problem lies in the relative insensitivity of the last part of the pig’s tail which can be chewed without its owner being aware of damage. Competition for feeding space or for drinkers leads animals which cannot be accommodated to chew the tails of those which can.
Boredom, disease and nutrition, especially low salt diets, feeding pellets or giving insufficient quantity may predispose. High concentrations of gases such as ammonia and carbon dioxide appear to predispose to tail biting. Air speed appears to be most important amongst the environmental influences. Once air speeds rise, pigs become restless and inquisitive and given to interact. One form of damage caused during this restless behaviour is tail biting.
The condition is not transmissible as such. It occurs when environmental and management conditions favour its appearance, but it does not develop in every batch of pigs.
The clinical signs of tail biting may be easy to identify. Groups in which tail biting is occurring are often restless, one or more individuals may be seen to bite the tail of another animals and damaged tails may be obvious. The victim often gives a short squeal or squeak when being bitten. Where pig densities are high, or where animals crowd to the front of a pen, tail biting may not be obvious. Fresh blood on the faces or bodies of pigs in the group may be seen.
Where individuals are clearly visible, the presence of fresh wounds on the ends of pig’s tails or the presence of blackish frayed or scabbed material indicates the presence of past tail biting. Animals with bitten tails may have the whole tail root bitten out or be paralysed. Affected animals often stand back from feeders and may be in poor condition.
The extent of tail biting should be determined, from mild lesions affecting only the tip of the tail to severe lesions exposing the contents of the pelvic cavity or causing paralysis. It is of importance to establish the age of the lesions, as old lesions may be mistaken for tail docking. The uneven length of the tails in a group will allow distinction. If old lesions are present and no longer active, then the point in production at which the problem arose should be determined.
The cause of the problem should be determined, if possible. Contributing factors such as competition for feeding space or for drinkers, boredom, disease such as diarrhoea, insufficient or poor quality food should be sought. Concentrations of gases such as ammonia and carbon dioxide should be measured and air speed over the pigs should be checked, particularly if there is a pen effect.
Tail biting can be confirmed at slaughter and its extent is most fully visible at post-mortem examination when evidence of ascending infection, spinal abscesses, pyaemia, and local abscesses at the root of the tail can be clearly seen after splitting the carcase. When pigs have died from the injuries, the lesions should be confirmed as having taken place before death, and not confused with damage caused to the carcase by cannibalism or by scavengers feeding on carcasses left outside.
Treatment of affected pigs must take place immediately. Badly affected animals should be moved from the pen and their wounds assessed. Where recovery is in doubt, the animals should be killed or sent for slaughter if old enough and fit to travel. The wounds should be disinfected and systemic antibiotic given.
Pigs with less severe wounds may be left, the pig responsible removed and the wounds dressed and antimicrobial given by injection. If more than one pig is responsible, then lowering the light intensity to make blood unattractive, spraying with a strong-smelling or foul-tasting product and urgent correction of the underlying problem should be carried out. The condition can be prevented to a large extent by docking the tails of piglets.
Tail docking can be helped by improving ventilation and especially reducing mean air speed, reducing humidity, reducing group size and the size variation within a group and by provide straw bedding, play chains, increase trough or feeder space or using single space feeders and improving quality or quantity of the feed. In some cases, the use of positive-pressure ventilation has been of value. The condition can still occur apparently without obvious reasons where all these factors have been addressed.