Artificial lighting programs in commercial poultry production manipulate birds' physiology and behavior to maximize production, often at significant welfare cost to the animals involved.
Lighting manipulation in poultry production treats birds as machines to be optimized rather than sentient animals with rest and behavioral needs. Near-continuous light in broiler houses prevents adequate rest and contributes to the leg problems that already affect a significant proportion of fast-growing birds. Early photostimulation in pullets causes injuries to immature reproductive tracts. The use of dim light to reduce activity is a welfare intervention that simultaneously hides suffering from inspection. Certification standards that require minimum dark periods and appropriate light intensity represent meaningful welfare progress.