The influence of adverse or gentle handling procedures on sexual behaviour in fearful and confident sows

Abstract

In the present study, the influence of handling during lactation on fear of humans and on sexual behaviour in the presence and absence of a human was investigated. Prior to handling, the sows were selected as being either fearful ( n=24) or confident ( n=24) towards humans based on their reactions to a human that entered their home pen. Within each group, half of the sows were handled either adversely or gently twice daily during the last 6 days prior to weaning until the end of the following oestrus. On the day of weaning, the sows were tested for their fear of humans in human approach tests in their home pen and in a novel arena. In order to determine when oestrus set in and whether ovulation took place, the back pressure test was performed by the stock persons from the fourth day after weaning and until the end of oestrus, and the sows were subjected to trans-rectal ultrasonographical scans from 12 h after onset of behavioural oestrus. Finally, a T-maze test was applied to investigate the sexual behaviour of the sows with and without the handler present on the third day after weaning until the end of oestrus. One of the stimulus compartments of the T-maze contained a boar and the other was empty. When the handler was present the handler stood in the goal area in front of the boar pen. The back pressure test and the trans-rectal scans revealed that all the sows came into oestrus during the experimental period. In the human approach test in the home pen the confident sows showed a significantly shorter latency to stay within 0.5 m of the handler ( P=0.02), to sniff the handler ( P=0.007) and to root ( P=0.04). The gently handled sows had a longer latency to freeze ( P=0.0001), shorter latency to root ( P=0.01), a tendency for shorter latency to stay within 0.5 m of the handler ( P=0.10) and to sniff the handler ( P=0.07) than the adversely handled sows. Handling and fear class affected the behaviour in the novel arena in a similar way. Thus, irrespective of fear classes, handling affected the sows and adverse handling generally made the sows more fearful of humans. The results of the T-maze test before oestrus revealed that the adversely handled sows and the fearful sows spent shorter time standing at the boar pen when the handler was present than when the handler was not present, whereas the opposite was the case for the gently handled sows and for the confident sows, respectively ( P<0.001). During oestrus, however, only the fearful sows that were handled adversely spent significantly less time close to the boar when the handler was present compared to when the handler was not present ( P<0.05), whereas all other sows spent an equal amount of time standing close to the boar whether the handler was present or not. Thus, in contrast to the pre-oestrus observations, during oestrus, adverse handling only affected the fearful and not the confident sows. This indicates that it is possible to improve oestrus behaviour and thus the possibility to detect oestrus by gentle handling of fearful sows.