Endocrine Abstracts

There is clear evidence in humans that stress during pregnancy has negative consequences on the foetus leading to greater susceptibility to disorders such as heart disease, diabetes type II and anxiety in adulthood. We aimed to assess whether stressors experienced by commercial pigs have a detrimental impact on piglet behavioural and neurophysiological development. Thirty-six primiparous sows were divided into control and two mixed groups that were stressed (social mixing) during either the second (Mix2) or third (Mix3) trimester of pregnancy. We found clear evidence of detrimental effects of mixing on the mothers' growth, body-lesions and cortisol levels. We did not observe any effect of mixing on gestation length, litter parameters and birth weight. At 60 days of age, 48 daughters were randomly selected from the three treatments: half were challenged using a restraint and isolation test. Then all were culled and brain tissue collected. In situ hybridisation measurements showed an increased expression of CRH mRNA in the PVN in unrestrained Mix2 daughters, and in the amygdala of both unrestrained and restrained Mix2 and Mix3 daughters. To induce further social stress, at 67 days of age, 24 more daughters randomly selected were mixed into groups of four. All showed an increase in salivary cortisol, but Mix2 and Mix3 showed a higher and longer elevation than controls. All 24 were inseminated and at parturition maternal behaviour was measured. Mix2 and Mix3 daughters were more restless during the pre-parturient period, and during parturition showed abnormal maternal behaviour. Mix2 daughters also showed a tendency to bite their piglets more than Mix3 and control daughters. This study provides evidence in the pig that stress experienced during gestation has long-lasting effects on offspring daughters, including their neurophysiological development and maternal behaviour. These findings indicate that pre-natal stress in the pig may have detrimental welfare consequences.