Prenatal stress in pigs: effects on growth, physiological stress reactions and immune function

During gestation, stressful stimuli may cause changes in the central nervous system of the fetal organism, which may finally affect endocrine and immune reactions of the neonates. The aim of the study was to examine the effects of a daily restraint of sows during the last third of gestation on endocrine stress reactions, immune responses and growth of the offspring. Stress and immune reactions of piglets were tested using an immobilisation and ACTH test at the ages of 3, 7, 21 and 35 days. Prenatally stressed piglets showed lower basal plasma cortisol and increased basal cortisol binding globulin concentrations at the age of 3 days compared to the control piglets. The prenatal stress treatment caused a decrease of glucocorticoid receptors in the hypothalamus, an enlarged adrenal cortex and a decreased thymus weight one day after birth. During the first days of life prenatal stress suppressed immune functions as shown by lower IgG levels and decreased in vitro lymphocyte responses to T cell and B cell mitogens. In addition, prenatally stressed piglets showed a higher mortality after birth and a tendency for lower birth weights. In general, morphological, endocrine and immune effects of prenatal stress treatment were only observed in piglets during the first days after birth. We suppose that prenatal stress during late gestation in pigs affects the ontogeny of the fetal neuroendocrine system mediated by repeatedly increased maternal stress hormone concentrations.