Light management profoundly affects broiler chicken welfare. Evidence-based lighting programmes provide dark periods for rest and support natural behaviour while improving health outcomes.
Continuous or near-continuous lighting in broiler houses causes significant welfare harm through sleep deprivation and circadian disruption. Chickens deprived of darkness cannot achieve normal sleep patterns, causing chronic fatigue and impaired immune function. Eye disorders including keratitis and cataracts are increased under continuous lighting regimes. The evidence that dark periods improve both welfare and production outcomes is robust — reducing sudden death syndrome mortality, improving leg health, and reducing eye disease — yet implementation of adequate dark periods remains inconsistent in commercial practice. Light intensity, colour spectrum, and uniformity also affect welfare. Dim rather than bright lighting during active periods reduces fear and aggressive behaviour. Evidence-based lighting programmes that provide 6-8 hours of darkness, appropriate intensity, and gradual transitions between light and dark represent achievable welfare improvements.