Effects of confinement duration and parity on behavioural responses and the degree of psychological fear in pregnant sows

The aim of this study was to evaluate the effects of space restriction stress on the behavior of different parity sows, and it is necessary to understand such effects due to space restriction to improve the welfare of the sows in confined conditions. We selected 264 pregnant sows (Large White) at primiparity, and at first to fifth parity in a commercial farm for the same due date (3 day ± 1.5). Behavioural observations and the novel object test (NOT) were carried out during the stages of confinement throughout their pregnancy. The results showed that there were no significant changes (p = 0.767; p = 0.761; p = 0.766; p = 0.960; p = 0.498) in standing, vacuum-chewing, bar-biting, trough-biting or rooting frequency of primiparous sows during the initial confinement (0-8 days). With the increase of the confinement duration, the vacuum-chewing frequency of the sows in all of the experimental groups increased significantly (p < 0.01) and the frequencies of fifth parity sows were significantly higher than those of the other groups (p < 0.01) throughout the entire stages of confinement. The rooting frequency of the experimental sows decreased continuously, and the younger groups (primiparity and first parity) had a significantly higher rooting frequency than the older groups (p < 0.01) from the 85th day of gestation. The NOT results showed that the frequencies and the durations of contact with the novel object of the older sows were significantly decreased from the 25th day to the 85th day of gestation (p < 0.01). The standing, bar-biting and trough-biting frequencies of all parity sows were decreased significantly (p < 0.01) after entering the farrowing pens. In conclusion, at least throughout the gestation period, short-term confinement will not cause adaptive changes in sow behaviour, but long-term confinement can significantly increase the frequency of vacuum-chewing and fear of novel stimuli.