How lighting conditions in poultry housing affect chicken welfare and what evidence-based standards are emerging.
Lighting management is a significant but often overlooked welfare determinant in poultry production. Chickens experience light differently from humans — their four cone types including UV perception mean that lighting adequate for humans may be visually inadequate or inappropriate for chickens. Historically, near-continuous low-level lighting suppressed sleep and maximized feed intake in broilers, creating chronic sleep deprivation. Welfare-appropriate lighting provides sufficient intensity for natural behavior expression, daily dark periods for normal circadian rhythm function, and gradual transitions that avoid startling responses. The evidence that appropriate lighting reduces fearfulness, reduces leg abnormalities from better activity levels, and improves overall behavioral indicators has driven changes in welfare certification standards. Minimum dark periods and adequate light intensity are now components of higher-welfare certification schemes.