Risk factors for vulva biting in breeding sows in south-west England.

A postal survey was conducted on 410 pig farms in south-west England to investigate the risk factors for vulva biting. The results of the bivariate analyses indicated that group housing, keeping a boar in the same pen and the number of sows per drinker were significantly associated (P < or = 0.05) with vulva biting in service sows. Group housing, group size, keeping a boar in the same pen, straw bedding, electronic sow feeders, feeding once daily, providing water automatically and the number of sows per drinker were significantly associated with vulva biting in dry sows. Vulva biting was also significantly associated with an increased percentage of culled sows and the occurrence of tail biting on the farm. A logistic regression analysis showed that group size and the number of sows per drinker were significant risk factors for vulva biting in service sows, and once a day feeding, group size, the number of sows per drinker and providing water automatically were significant risk factors for dry sows.