Published online by Cambridge University Press: 01 January 2023
Artificial rearing involves removing piglets from their mother at seven days of age and feeding them milk replacer until weaning. Early-life rearing conditions can influence piglets’ mental development, as reflected by their emotional state and reactivity. This study compared the post-weaning emotional state and reactivity of pigs which were either sow-reared or artificially reared pre-weaning. Behavioural tests (startle test, novel object test, human-animal relationship test and open door test) were conducted one week post-weaning (weaner 1, 34 [± 0.6] days old), one week after movement to weaner 2 (69 [±1.2] days old) and to finisher (100 [± 1.3] days old) stages. Qualitative Behavioural Assessments (QBA) were conducted on the same days in weaner 2 and finisher stages. QBA descriptors were computed by PCA and all other data were analysed using linear models. Artificially reared pigs were less fearful of human contact in weaner 1 (45.1 [± 8.43] vs 81.3 [± 7.89]%) and finisher (25.8 [± 5.19] vs 45.7 [± 6.00]%) stages; but there was no difference in the other tests. Artificially reared pigs had a higher QBA score (more positive) than sow-reared pigs in weaner 2 (54.49 [± 10.102] vs 17.88 [± 9.94]) but not in finisher (70.71 [± 8.860] vs 52.76 [± 9.735]) stage. In conclusion, artificially reared pigs appeared to have a more positive emotional state transiently post-weaning and a lower fearfulness towards humans, which are likely mediated by their pre-weaning conditions. These data emphasise the need to consider the entire life of the animals to fully evaluate the long-term impacts of a rearing system.