Behavioural priorities of laying hens

This article reviews the behavioural requirements of laying hens. It primarily concentrates on evidence from consumer demand studies and relates this to the behavioural and physical consequences of denying hens opportunities to express certain activities. Hens clearly place a high value on food and this provides a useful yardstick for assessing the value of other resources. Hens have been found to work for access to a range of additional resources including pecking, scratching and dust bathing substrates, perches (particularly prior to nightfall), additional space and nestboxes. So far, only nestboxes (prior to oviposition) have been found to have a value comparable to food (in food-deprived hens). To date, however, no study has systematically compared the value of a range of resources. Furthermore, only a limited number of studies have related deprivation of specific resources to behavioural or physiological measures of distress. Egg production is clearly very efficient economically when hens are housed in conventional wire cages and provided with adequate food and water, but the hens show signs of frustrated nesting and pecking/scratching behaviour in these conditions. Modified or enriched cages allow for these activities, as well as perching, and, potentially dust bathing, but do not allow full expression of exploratory or comfort behaviours. Free-range systems, percheries and other types of colony housing provide opportunities for all of the above, although at high stocking densities social competition and limited space may restrict performance of these behaviours for certain birds.