Prenatal stress : state of the art and possible consequences for farm animal husbandry

Abstract

Stress that occurs during pregnancy can have consequences on the behaviour of offspring such as increased emotional reactivity, impaired learning ability and feminisation of male sexual behaviour. A modification of the hypothalamo-pituitary axis is often observed, for example, an increase in basal glucocorticoid concentrations and a higher secretion rate after a stressful event. Immune responses can also be modified, and birth-weight reduced. However, there is a high level of variability in the effects of prenatal stress. This may be due to the type of stressor, its intensity and period of application during pregnancy. The effect may also differ according to the gender of the offspring, with females appearing to be more affected than males. Stress experienced by a dam during pregnancy could have consequences on neuroendocrine development in the foetus. Maternal hormones secreted during stress, which can cross the placental barrier, could be one of the mechanisms explaining these effects. Modification of maternal behaviour due to chronic stress may also be involved in the effect on the behaviour of the offspring. Most studies have been performed on rodents and primates but the few experiments involving farm animals tend to show that the consequences can be important.