Accumulation of maternal and prenatal stress on immune function, stress response, and microbiome

Exposure to maternal cortisol during gestation can induce fetal programming, affecting progeny well-being. Despite advancements in the swine industry, stress among pregnant gilts and sows remains prevalent, with research highlighting its effects on offspring immune function and stress responses. However, the influence of stress timing and its long-term effects, particularly during progeny adulthood and pregnancy, remains poorly understood in pigs compared to humans.This dissertation explores how maternal stress, particularly its timing, affects progeny immune and stress responses. The first chapter describes the optimization of a psychological stress model to induce chronic stress through oral administration of synthetic cortisol, effectively elevating maternal cortisol levels in early, mid, and late gestation sows. Although initial findings revealed alterations in progeny immune and stress responses, sample limitations warranted further investigations. Subsequent chapters examined the effects of prenatal stress on hypothalamic gene expression and progeny responses to weaning stress and Adrenocorticotropic hormone (ACTH) challenges. Piglets from mid-gestation hydrocortisone acetate-treated sows (M-HCA) exhibited reduced interleukin-1a gene expression, potentially explaining altered immune responses, while late-gestation HCA-born offspring (L-HCA) showed reduced expression of stress-axis genes. Finally, the dissertation also assessed the generational effects of prenatal stress. Piglets born to prenatally stressed sows displayed distinct immune changes, particularly when their mothers experienced no pregnancy stress. Up- and down-regulation of immune-related genes were observed, depending on stress timing, with some effects persisting across generations, especially under additional stress during pregnancy. These findings emphasize the need for further research to develop interventions that mitigate prenatal stress impacts. Ultimately, this work highlights the importance of understanding maternal stress and its long-term implications on progeny, as it can significantly impact the health and well-being of breeding and marking animals, thereby influence the sustainability and productivity of the swine industry.