Lighting conditions in broiler houses significantly affect bird welfare. Provision of light periods that allow normal rest and activity rhythms improves welfare outcomes.
Lighting is a welfare variable that has historically been manipulated entirely for production benefit — maximizing time available for feeding. The welfare costs of inadequate darkness include compromised sleep, disrupted circadian rhythms, elevated chronic stress, and ocular damage in some systems. Research consistently shows that lighting regimes with adequate dark periods and, where possible, natural light provision produce healthier, better-rested birds with better leg health and lower fearfulness. These welfare improvements often align with better performance outcomes, but even where a modest production trade-off exists, the welfare case for adequate light and dark provision is compelling.