Factors identifying pigs predisposed to tail biting

Approximately 5% of pigs slaughtered in the UK have been tail-bitten, leading to welfare and production issues. Tail biting is sporadic and not all pigs tail bite. The aim of this study was to identify factors that are common in pigs that perform tail-biting behaviour, and that might be used in a predictive way to identify such animals. The behaviour of 159 pigs was observed in the post-weaning period. Pigs were weaned at 4 weeks of age. In the week prior to weaning and at 6 weeks of age each pig was individually tested in a tail chew test (tail chew test 1 and 2, respectively). The tail chew test involved recording the pig’s behaviour directed towards two ropes, one of which had been soaked in saline solution and the other not. The production performance of the pigs was recorded from birth to 7 weeks of age. Time spent performing tail-biting behaviour correlated positively with time in contact with the rope in tail chew test 2 (r = 0·224, P<0·05), and time spent ear biting correlated positively with time spent in rope directed behaviour in tail chew test 1 (r = 0·248, P<0·01). Pigs that spent as much as 1·5% of their time of more performing tail-biting behaviour were lighter at weaning (26 days) and tended to be lighter at 7 weeks of age compared with pigs that spent less than 1·5% of their time performing tail-biting behaviour (weaning weight : ≥1·5% tail biting 8·96 kg, < 1·5% tail biting 9·67 kg, P<0·05; 7-week weight : ≥1·5% tail biting 15·75 kg, < 1·5% tail biting 17·09 kg, P<0·08). There was no signifi cant difference in birth weight between pigs that spent ≥ or < 1·5% of their time performing tail-biting behaviour. Pigs that spent 1·5% of their time or more performing tail-biting behaviour showed signifi cantly lower growth rates between birth and weaning ( ≥ 1·5% tail biting 260 g/day, < 1·5% tail biting 285 g/day, P<0·05) but not between weaning and 7 weeks of age ( ≥ 1·5% tail biting 343 g/day, < 1·5% tail biting 365 g/day, P>0·05). The results suggest that pigs that tail bite have some nutritional defi ciency that results in performance of foraging behaviour that is expressed in intensive housing as ear/tail biting.