The lighting conditions in which broiler chickens are raised profoundly affect their welfare. Inadequate lighting leads to fearfulness, disrupted sleep, and developmental problems.
Broiler chickens in near-darkness are inactive, fearful when exposed to light, and cannot express natural foraging and exploratory behaviour. The industry uses low light to reduce activity and promote faster weight gain, but this creates environments of sensory deprivation. Chickens need appropriate light to synchronise circadian rhythms, maintain normal sleep, and engage in social behaviour. Light deprivation is a form of environmental impoverishment with significant welfare costs that is now regulated but incompletely enforced.