Influence of housing and social changes on growth, behaviour and cortisol in piglets at weaning.

The present experiment aimed at evaluating the relative effects of environmental and social changes on behaviour, growth and salivary cortisol of piglets at weaning. On Day 0, 26-day old piglets were weaned and allocated to one of four treatments: neither environmental nor social change (C), environmental change (E), social change (S), and both changes (SE). Overall, 6 replicates of 10-12 animals/pen/treatment were analysed. Piglets were video recorded during the first three days after weaning to observe social behaviour and general activity. Saliva was collected between 07:00 and 09:00 on Day 0 just before weaning (D0H7), on Day 1 (D1H7) and Day 2 (D2H7 and D2H16) to measure cortisol. Saliva cortisol did not change after weaning in C piglets but increased significantly at D1H7 in S and SE piglets, at D2H7 and D2H16 in E and SE piglets. Compared to C piglets, numerous behaviours were altered in SE piglets: more total lying (P<0.08), less lying on the belly, less environmental exploration, less playing, more fighting regardless the day, more lying awake inactive on Day 0 (P<0.05). Compared to C piglets, E piglets displayed more total lying but less environmental exploration whereas S piglets showed less lying on the belly but more fighting (P<0.05). Present results show that moving piglets to a new environment as well as mixing them with unfamiliar conspecifics at weaning have stressful effects which are additive.