Tail biting behaviour and tail damage in pigs and the relationship with general behaviour: Predicting the inevitable?

Tail biting behaviour in pigs is a common problem in conventional housing systems. Our study examined the consistency over time in tail biting and tail damage and it explored the predictive value of general behaviours observed in individual pigs and in pens as a whole. Pigs (n = 480), reared in conventional farrowing pens with a sow crate, were followed from pre-weaning to slaughter (23 weeks). Post-weaning, piglets were housed barren (B) or enriched (E). Behaviours were observed pre-weaning (averaged per litter) and post-weaning in three phases (weaner, grower, finisher) (averaged per pig/phase). Tail damage of individual pigs was scored weekly from weaning (4 weeks) onwards (averaged per phase). Relationships between tail biting and tail damage with behaviour were investigated both at individual and pen level using mixed or generalized linear mixed models and Spearman's rank correlations, respectively. Tail biting and tail damage (2.1 ± 0.05, 1 = no tail damage, 4 = tail wound) were already observed pre-weaning. Post-weaning, tail biting and tail damage were less prevalent in E compared to B housing (P <0.001). Tail biting behaviour in individual pigs was not consistently observed over time, i.e. none of the pigs was tail biter in all three phases, so new tail biters were found in later phases and some of the already identified tail biters stopped tail biting completely or temporarily. In B housing 38.3% and in E housing 5.6% of pigs was identified as tail biter in at least one phase post-weaning. B housed tail biters in different phases were likely to originate from litters with a relatively high level of tail biting behaviour pre-weaning (P <0.05–0.01). Generally, post-weaning victims were likely to be a victim again in successive phases of life (B: P <0.10–0.001; E: P <0.01). Tail biting and tail damage were best predicted by behaviours at pen level and less by behaviours at the individual level: a higher activity, and more pig and pen-directed manipulative behaviours were observed in pens with high levels of tail biting. Particularly higher levels of chewing or consuming objects such as jute sacks could be useful in predicting tail bite outbreaks. To conclude, tail biting in pigs starts early in life and is difficult to predict due to its inconsistency, although tail damage is more consistent throughout life. Especially behaviour observed at litter or pen level is a promising tool in predicting tail biting and tail damage.