Seasonal infertility, stress and adrenocortical responsiveness in pigs

Abstract

This study was undertaken to study the hypothesis that ‘seasonal’ or ‘summer’ infertility in commercial piggeries was a result of a stress response of individual pigs to a variety of stressors in their environment, and that certain individuals, because of their high adrenal responsiveness were more ‘at risk’ of suffering infertility. Pigs from four herds, with a history of infertility occurring during late summer to early autumn were studied over this period and over the cooler months of winter and spring. The results confirm the complexity of seasonal infertility. As expected, infertility occurred in summer on three farms, while on the fourth farm the seasonal infertility unexpectedly occurred in winter. This study provides the first tentative evidence for a relationship between seasonal infertility and a stress response mediated by factors other than heat stress or photoperiod. Furthermore, it was found that individual pigs with a high potential adrenal responsiveness to stress were more likely to suffer from seasonal infertility. The association between the adrenal responsiveness and the severity of seasonal infertility suggests a way to reduce the incidence of seasonal infertility by selecting for pigs with low stress responsiveness.