Weaned piglet’s reactivity to humans, tonic immobility and behaviour in a spatial maze test is affected by gestating sows’ relationship to humans and positive handling at weaning

Abstract

Fear of human can impact negatively offspring’s behaviour and cognition whereas early positive handling has positive impacts. The aim of this study was to evaluate the crossed effects of trans-generational transfer and familiarisation with human on piglets’ behaviour. Sows were classified into two categories (Fearful, n = 11 and Docile, n = 13) based on whether they avoided human contact or not during a human approach test at 71 days of gestation. Fear of human was not related to salivary cortisol levels of the sows (F =2.72, P = 0.10). Fearful sows’ piglets stood immobilized longer (Chisq= 6.24, P = 0.01), as well females (8.70, P = 0.003) during a tonic immobility test (TIT) at 7 days but not at 15 days. The behaviour of two male and two female piglets per sow (n = 96) was studied after weaning (28 days). We found no effect of sow’s reaction to human on piglets’ emotionality expressed during an open-field test (OFT) at 32–33 days. However, during a Human voluntary approach test (VHAT) piglets born from fearful sows were more fearful than piglets born from docile sows (Chisq=8.23, P = 0.004,). Half of the piglets (n = 48, 1 male and 1 female per sow) were then familiarised with human while the others received minimum contact. We found no main or crossed effect of sow’s reaction to human and piglet’s treatment on piglets’ emotionality during an OFT, nor on their exploratory behaviour during VHAT at 46–47 days. Piglets’ born from fearful sows were less attracted to human during VHAT2 (Chisq=8.33, P = 0.004) and familiarised piglets were more attracted (Chisq=15.05, P < 0.001). Piglets born from docile sows found the reward faster in a spatial maze test than those born from fearful sows. Both sows HAR and piglet familiarisation with human seemed to specifically affect human related behaviours without affecting their general emotionality, but also behaviour in a spatial maze test.