Hormones and husbandry: control of nesting behavior in poultry production

Nesting behavior in laying hens is controlled by an interaction of internal and external factors. Initiation of nesting is under hormonal control, but the exact timing, location, and form of the behavior are all affected by husbandry practices. These have important effects on the economics of poultry production. Nesting behavior is triggered by ovulation. Estrogen and progesterone released from the post ovulatory follicle result in the initiation of nest site selection and nest building about 24 hr later. Oviposition then occurs, although it may be delayed by factors such as feeding or disturbance. Selection of nest site is important in deep litter systems, where eggs must be laid in nest boxes for efficient collection. Both the ability of hens to reach nest boxes, and their preference for boxes rather than the floor, are affected by husbandry. Genetic selection, rearing conditions, and design of houses and nest boxes all influence this behavior in different ways. In some circumstances hens show intensive activity before laying. This is particularly common when light hybrids are housed in battery cages: apparently cages do not provide adequate stimuli for sitting and nest building in these birds. This activity is wasteful of energy and may indicate reduced welfare. The problem may be reduced by modification of the environment or selection of stock.