Maternal corticosterone elevation during egg formation in chickens (Gallus gallus domesticus) influences offspring traits, partly via prenatal undernutrition.

The relationship between maternal stress during pregnancy in humans and the subsequent physical and mental health disorders in their children has inspired a wide array of studies on animal models. Almost all of these studies have used mammalian species, but more recently oviparous species in which the embryo develops outside the mother's body have received more attention. These new models facilitate disentangling of the underlying mechanism due to the accessibility of the prenatal environment, the egg. Studies in birds have found that maternal stress during egg formation induces phenotypic alterations in the offspring that hatch from these eggs. However, different offspring traits have been measured in different studies and potential underlying mechanisms are barely addressed. In this study we experimentally manipulated maternal corticosterone levels in laying hens. We found that mothers with experimentally elevated plasma corticosterone levels produced offspring that are smaller at hatching, less competitive, less fearful, have lower immunocompetence and higher plasma testosterone levels, as well as an alteration of visually guided behavioural lateralization. Earlier we have showed that eggs produced by these corticosterone treated mothers were lighter and contained lower concentrations of testosterone and progesterone in the yolk. While yolk hormones showed no correlation with any offspring traits, egg mass correlated positively with offspring's body mass from hatching until 10days of age and hatching mass correlated positively with the offspring's ability to compete for food, indicating that prenatal under nutrition might mediate some effects of maternal stress.