Tail posture predicts tail damage among weaned piglets

Tail biting in pigs is a widespread behavioural vice with significant animal welfare and economic consequences. All too often, tail biting is not diagnosed nor dealt with until tail damage is present. To effectively reduce the negative effects of tail biting, it must be diagnosed in an early stage. So far no predictors for tail damage have been found. Predictors that recognise tail biting in an early stage, however, would be helpful in practice. We tested the hypothesis that tail behaviour can predict tail damage. To analyse this, we observed tail posture, tail motion and tail damage of 992 weaned piglets on an experimental farm with known tail biting problems. Tail posture (curled tail, hanging tail or tail between legs), tail motion (motionless, wagging or intense wagging) and tail damage (no damage, bite marks or a tail wound) were observed three times a week during the 32 days post-weaning period. Results showed that both tail posture and tail motion were related to tail damage at the same observation moment ( P < 0.001). Furthermore, tail posture could predict tail damage ( P < 0.001), but tail motion had no predictive value for tail damage ( P > 0.05). When a piglet was observed with a curled tail (and no tail damage), the chance of bite marks or a tail wound 2–3 days later were 8.6% and 3.5%. When a piglet was observed with its tail between the legs (and no tail damage), the chance of bite marks or a tail wound 2–3 days later increased to 22.3% and 8.5%. Furthermore, when a piglet was observed with its tail between the legs (and no tail damage) in two consecutive observations, the chance of bite marks or a tail wound 2–3 days later increased to 32.4% and 23.7%. It was concluded that a piglet's tail posture is strongly related to tail damage at the same moment and can predict tail damage 2–3 days later. Checking tail postures on a regular basis increases early recognition of tail biting. This can help pig producers to take appropriate measures to prevent further escalation of the problem.