Impact of prenatal stress and environmental enrichment prior to weaning on activity and social behaviour of piglets (Sus scrofa). By Sophie Brajon, Nadine Ringgenberg, Stephanie Torrey, Renée Bergeron, Nicolas Devillers, 2017. Applied Animal Behaviour Science 197: 15-23.
• Prenatal stress (PNS) can have detrimental effects on piglets behaviour and welfare.
• Pre-weaning enrichment may compensate negative effects of PNS in piglets.
• PNS effects were delayed after weaning at d 27 as shown by an increased inactivity.
• Enrichment had positive effects but its removal at weaning affected behaviour.
• Pre-weaning enrichment did not compensate for the effects of PNS.
Prenatal stress (PNS) can have detrimental effects on behaviour and welfare, such as decreased exploration. Whether housing enrichment before weaning compensate negative effect of PNS in commercial pigs is unknown. To address this question, 44 sows were assigned to either a mixing stress (T) or a control (C) treatment in mid-gestation. During lactation, half of the T and C sows were housed with their 12-piglets litter in straw enriched pens (E) while the others were housed in standard farrowing crates (S). At weaning, 6 piglets per litter were selected and moved to non-enriched standard pens. Lying down, exploration and social behaviour were recorded in the home-pen before weaning (d 6, d 12, d 20), on the day of weaning (d 21), and after weaning (d 22, d 27) using scan and one-zero samplings. Three piglets per litter were individually subjected to a social isolation test and a social confrontation test at d 17. Data were analysed by day using mixed models with PNS, housing enrichment and their interaction as fixed effects. We found no interaction between the treatments, suggesting the absence of a compensatory effect of enrichment on PNS. Pre-weaning enrichment promoted exploration (P< 0.004) and seemed to improve comfort, as piglets spent more time lying down (P< 0.02), but was associated with reduced locomotion and play fighting (P< 0.03) compared to no enrichment. After weaning, E piglets explored less (P< 0.01) and played less (locomotion and fighting play: P< 0.0003) than S piglets. They also performed more belly-nosing at d 27 (P =0.04). These results support the idea that the removal of enrichment at weaning negatively affects piglets. The E piglets exhibited higher emotional reactivity than S piglets (i.e. more high-pitched calls and escape attempts) during the social isolation test, but no clear effect was observed during the confrontation test. The effects of prenatal stress on behaviour were only apparent after weaning. On d 27, T piglets spent more time lying (P =0.02), and showed reduced exploration (P =0.004), locomotion play (P=0.03), fighting play (P=0.04) and mounting behaviour (P =0.002) than C piglets. In conclusion, both prenatal stress and pre-weaning enrichment affected piglet behaviour, but a compensatory effect of enrichment on the negative effects of prenatal stress could not be demonstrated.