Light management in poultry housing profoundly affects broiler and laying hen welfare through its influence on behavior, health, and biological rhythms.
Continuous or near-continuous artificial lighting in intensive poultry houses disrupts the circadian biology of birds that evolved to live with natural day-night cycles. Eye damage including cataracts occurs in a proportion of broilers kept under continuous light. The suppression of natural rest-activity cycles causes physiological stress. Dark periods allow birds to rest and recover from the high metabolic demands of intensive growth. Minimum dark period regulations represent an important welfare floor, but best practice involves more sophisticated lighting programs with appropriate light levels, spectrum, and distribution throughout the day.