Abstract
Injurious pecking in laying hen flocks comprises feather pecking and tissue pecking, the latter often referred to as cannibalism. Although some gentle feather pecking belongs to the natural repertoire of laying hens, the more vigorous form, severe feather pecking, is considered an abnormal behaviour. Various theories have been developed to explain the onset of injurious pecking. All point to suboptimal circumstances leading to abnormal or redirected behaviour. A wide range of husbandry and management factors have been identified. They affect either the onset of injurious pecking (prevention) or its reduction. Prevention is most important, because once started the behaviour is very hard to stop. Therefore the first focus should be on optimizing rearing conditions to prevent injurious pecking. The most important management strategy in rear is a continuous presence of high-quality substrate to stimulate foraging behaviour and to allow the pullets to develop a habit of directing their pecking towards the litter. Any stressor can be a trigger for injurious pecking. This means management should also focus on the prevention of stressful events. Such stressful events may be changes in housing conditions (e.g. transition from rear to lay, climate) and management (e.g. light, feed, access to range), but also suboptimal health, especially parasites and compromised intestinal health. Finally some husbandry conditions seem to increase the propensity to develop injurious pecking, such as large flock sizes and a higher bird density. Management to prevent injurious pecking can only be successful if it aims at optimizing all factors involved.