Effects of confinement duration and parity on stereotypic behavioral and physiological responses of pregnant sows

The aim of this study was to evaluate the effects of space restriction stress on the stereotypic behavioral and physiological responses 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 fifty pregnant sows (Large White) at primiparity and first to fifth parity in a confined farm with the same body condition and due date (3 ± 1.5 days). Behavioral observations and physiological analysis were carried out during spatial confinement throughout pregnancy. The results showed that there were no significant changes in vacuum-chewing, bar-biting, trough-biting and the concentrations of serum IL-6 in primiparous sows during the initial confinement (0-8 days). With the increase of the confinement duration, the serum cortisol, IgA, IL-6 concentrations and the vacuum-chewing frequency of sows in all groups increased significantly, and the serum concentrations of C-reactive protein and Pig-MAP increased significantly except for the sows in the first and second parity groups. The serum cortisol, IgA, IL-6 concentrations and the vacuum-chewing frequency of older sows were significantly higher than those of the young sows throughout the entire restricted feeding period, but the serum C-reactive protein concentrations of primiparous gilts was significantly higher than those of the other groups. The serum cortisol, IgA, IL-6 concentrations and bar-biting and trough-biting frequencies of all parity sows decreased significantly after entering the delivery bed. In conclusion, long-lasting and recurrent environmental constraints can significantly increase the frequency of stereotypical behavior and serious psychological and physical stress, seriously damaging sow welfare.