Genetic selection to reduce stress in animals

Where no further improvements in the rearing environment can be achieved, or where novel species are being subjected to intensive rearing practices, consideration may be given to optimising welfare by altering the sensitivity of the animal itself to potentially stressful stimuli. Given that over-stimulation of the hypothalamic-pituitary-adrenal (HPA) axis is associated with deleterious effects on growth, reproductive performance and disease resistance, reduction of stress responsiveness may reduce ‘inappropriate’ effects of frequent or continuous exposure to stressful stimuli. How might a reduction in responsiveness be achieved? Domestication represents the outcome of a long-term ongoing selective breeding programme, to some extent both deliberate and inadvertent. It has been proposed that selective breeding may offer a route by which the incidence of behaviours and responses associated with welfare problems (and by association, performance) might be reduced. This article provides an account of the factors involved in modifying the activity of the stress axis in animals by selective breeding.