Aggression and feather pecking in laying hen flocks causes significant injuries and welfare harms. Managing flock density, genetics, lighting, and enrichment reduces aggressive behaviour.
Feather pecking and aggression in laying hens represent a welfare problem with no simple single solution — effective management requires addressing multiple factors simultaneously. The root causes of feather pecking are primarily motivational: hens frustrated in foraging and dust bathing redirect oral exploration toward flock-mates' feathers. Once blood is drawn, the behaviour spreads rapidly as other hens are attracted to the wound. Beak trimming prevents the worst injury outcomes but causes acute and possibly chronic pain, and addresses the consequence rather than the cause. The more welfare-positive approach combines appropriate diet (adequate amino acids to reduce feather pecking motivation), enriched environments with foraging substrate, optimal lighting that reduces visual contrast that triggers pecking, appropriate flock sizes and densities, and genetics selected for lower pecking propensity. This multifactorial approach requires more management skill but produces hens with better overall welfare than beak trimming in barren environments.