Lighting management in broiler production profoundly affects circadian rhythm, sleep, activity, and welfare, with standard commercial programmes often prioritising feed conversion over biological needs.
Lighting management in broiler houses is a welfare lever with disproportionate impact for its low implementation cost. Continuous or near-continuous light exposure prevents the normal circadian rhythm that coordinates metabolic, immune, and musculoskeletal development in birds. Broilers on continuous light programmes show disrupted sleep architecture; sleep deprivation has known welfare and health consequences in all animals studied. The resulting welfare harms include higher rates of ascites, sudden death syndrome, and leg problems that cause chronic pain. These effects are additional to the underlying problems caused by fast-growing genetics; lighting management interacts with genetic susceptibility to amplify harm. Providing a minimum of 6 hours of darkness at the same time each day is a simple, low-cost intervention that measurably reduces welfare harms across multiple body systems. EU legislation already requires this; global harmonisation of this minimum standard would benefit hundreds of millions of birds annually.