Lighting programmes in poultry houses have major effects on broiler behaviour, health, and welfare, with significant variation between intensive and higher-welfare systems.
Lighting management in broiler houses is a largely invisible welfare lever that significantly shapes the lives of billions of chickens annually. Continuous or near-continuous lighting driven by growth maximisation goals deprives birds of rest and disrupts natural circadian biology. Very dim lighting reduces stress-related aggression but also suppresses the activity that supports leg health. Higher-welfare lighting programmes that provide adequate darkness, appropriate intensity, and natural-spectrum light produce birds that are more active, healthier, and have better bone and muscle condition. These improvements come at modest cost and represent one of the more achievable reforms in broiler production.