Rope test may indicate efficacy of tail-biting treatments in growing pigs

Tail biting is a most serious welfare problem in pigs raised for slaughter. In instances of an outbreak of tail biting, scientists have recommended that farmers take measures such as removal of affected animals, provision of enrichment materials and application of repellents to the pigs' tails. However, no scientific study has ever confirmed the efficacy of any of these suggestions in counteracting an ongoing outbreak. Here, the efficacy of two repellent ointments, Dippel's oil and Stockholm tar, were examined in a tail-chew test. For this, a novel piece of nylon rope was used as a tail model to measure biting behaviour semi-automatically in 24 single-sex groups of growing pigs (total 264 pigs). Repeated measures analysis showed no effect of time, gender or unit (12 pens per unit), but a highly significant effect of treatment, in that both Stockholm tar and Dippel's oil significantly reduced rope manipulation compared to controls. These results suggest that Stockholm tar and Dippel's oil may be effective in reducing tail biting. The approach taken may be valuable in further testing of strategies to reduce tail biting and improving pig welfare.