Effect of timing of prenatal stress on social behavior and immune phenotype of piglets

Prenatal stress has been shown to have a considerable impact on the postnatal period in piglets, primarily attributed to high maternal and fetal cortisol levels at the maternal-fetal interface, which can cross the placental barrier, exposing the fetus to very high levels (Merlot et al., 2013). The impact of stress on the progeny varies depending on the time of its occurrence during gestation, as different developmental processes, such as the brain and immune system, unfold at distinct gestational stages. Stress experienced during mid-gestation is more likely to influence the development of the immune system, given that the differentiation of immunoglobulin-secreting cells and T-cells begins in the second trimester (mid-gestation). Consequently, maternal stress during these critical or vulnerable periods can adversely affect the immune phenotype and social behavior of the progeny, considering the interconnection between immune and behavioral traits (Mafoz, 2020). Therefore, this study aimed to evaluate the effects of prenatal stress during mid-gestation on the social behavior and immune phenotype of piglets born to stressed sows. This research is important as it can help improve the health and well-being of swine while serving as a valuable model for examining prenatal influences on human conditions due to the similarities in brain structure and development. Eleven Yorkshire × Landrace crossbred gilts were artificially inseminated using semen from a single Landrace boar. They were randomly assigned to receive either hydrocortisone acetate (HCA), a synthetic glucocorticoid, or a placebo capsule during mid-gestation (days 51–72). On gestational day 110 (before farrowing), all gilts were moved to individual farrowing stalls, remaining through a 21-day lactation period. Blood samples were collected from piglets born to these primiparous sows at 7, 14, and 21 days of age, and plasma cortisol, cytokines, stress biomarkers, and immunoglobulin concentrations were analyzed. Behavioral observations were conducted 24 hours after blood sampling at 7, 14, and 21 days of age and registered at 2-hour intervals across four defined periods. However, only data collected at 7 days of age will be presented. Frequencies and durations of social behaviors were registered and analyzed along with physiological biomarkers to determine the impact of prenatal stress during mid-gestation on the offspring. These data imply that piglets born to sows exposed to mid-gestational prenatal stress exhibited more negative social interactions, heightened activity, and immunoenhancing and immunosuppressive effects than the controls.