Lighting conditions in poultry houses significantly affect broiler and layer welfare through effects on behavior, health, and circadian rhythm. Evidence-based lighting is a key welfare variable.
Lighting welfare for poultry operates at the intersection of circadian biology and behavioral need. Near-continuous light that maximizes growth rate does so by preventing normal sleep and rest cycles that are biological requirements, not preferences. The consequence is chronic physiological stress - elevated stress hormones, impaired immune function, and the skeletal and cardiovascular problems associated with insufficient rest. The welfare impact is most severe in broilers bred for extremely fast growth where the birds' physiology is already strained. Evidence-based lighting that allows natural circadian rhythms improves welfare outcomes measurably and is one of the simplest and most cost-effective welfare improvements available in commercial poultry production.