Tail biting in pigs: (in)consistency, blood serotonin, and responses to novelty

Tail biting is usually considered a persistent maladaptive behaviour in pigs. We investigated whether the tendency to develop tail biting is related to peripheral serotonergic functioning and personality characteristics of pigs. Pigs (n=480 in five rounds) were kept in conventional farrowing pens until weaning at 4 weeks of age. Thereafter, they were housed barren (B) or straw-enriched (E). Individual pigs were exposed to a back test, a novel environment test and a novel object test in an unfamiliar environment at 2, 3.5 and 13 weeks, respectively. Blood serotonin measures were determined at 8, 9 and 22 weeks. In different phases (nursery, grower and finisher), pigs were classified as (non) tail biter based on tail biting behaviour, and as (non) victim based on tail wounds. Consistency of this classification over different phases was assessed with generalized linear mixed models. Effects of housing and associations between tail biter and victim status, blood serotonin and responses to novelty were, per phase, analysed using mixed models. Pigs were not consistently classified as tail biter over all phases post-weaning, but being a victim was (B: P