Some behavioural deviations in weaned domestic pigs: persistent inguinal nose thrusting, and tail and ear biting

Abstract

Groups of pigs were observed from weaning to marketing for the incidence of tail and/or ear biting and persistent inguinal nose thrusting. The 16 groups included single and mixed litters, single or mixed-sex ratios, and comprised up to 12 pigs; 14 of the groups showed biting behaviour and 12 groups showed persistent inguinal nose thrusting behaviour. The onset of biting appeared from 0 to 44 days after weaning, and persistent inguinal nose thrusting was first observed 4 to 22 days after weaning.There was a significant relationship between the number of pigs biting and being bitten in a group. The high ranks tend to bite middle and low ranks more than expected, the middle ranks bite other middle ranks more than expected, and low ranks bite the least. Within any rank there was no difference between male and females biting or being bitten. The most common situation was to have, in a group, some pigs which only tail bit, others that only ear bit, and others which both tail and ear bit. It is suggested that biting is a learned response spread by visual communication, so that visual barriers around affected groups may help to limit the spread of an outbreak.In persistent inguinal nose thrusting behaviour, rank was important, as the top ranking pigs were the most most likely to show persistent inguinal nose thrusting. Persistent inguinal nose thrusting may have its origin in udder seeking, exploratory or rooting behaviour, but becomes used mainly by dominant pigs. The behaviour is halted by the pig which received the nose thrusts moving away.