In the journal, Animal Welfare, Camilla Munsterhjelm at the University of Helsinki in Finland and co-authors there and at the Swedish University of Agricultural Sciences report a recent study aimed at identifying differences in stress measures in pigs with different roles during a tail-biting outbreak.

Quartets (n=16) of age- and gender-matched fattening pigs including a tail-biter (TB; n=16), a victim (V; n=16), a control in the same pen (Ctb; n=10), and one in a pen without tail biting (Cno; n=14) were chosen by direct behavioural observation.

Stress measures used were behaviour (dog-sitting, sniffing of pen-mates and aggression), thyroid hormone concentration, morphology of adrenal and thyroid glands and salivary cortisol concentration sampled at 07:00, 10:00, 16:00 and 19:00h. Category (TB, V, Ctb, Cno) effects were investigated using a mixed model with replicate as subject and category as repeated effect.

Category had a significant effect on adrenal total (cortex + medulla) and cortical area, salivary cortisol at 19:00h, serum triiodothyronine (T3) and the behaviours performing and receiving sniffing.

Victims suffered from a triad of chronic stress, pathology and suppressed T3 secretion.

Evidence for stress in tail-biters, a possible cause of the behaviour, consisted of a slightly flattened day-time cortisol pattern and more performed sniffing than all other categories. Differences in evening cortisol concentration and T3 levels between the categories in the pen with ongoing tail-biting emphasise the qualities of the control animal.

These differences, conclude Munsterhjelm and co-authors, support the view that neutral pigs represent a phenotype that adopts a coping strategy leading to lower stress levels than in tail-biters and victims, despite being housed in the same pen.

Reference

^{Munsterhjelm C., E. Brunberg, M. Heinonen, L. Keeling and A. Valros. 2013. Stress measures in tail biters and bitten pigs in a matched case-control study. Animal Welfare. 22: 331-338. doi: 10.7120/09627286.22.3.331}

August 2013