Reptiles require appropriate UV-B light for vitamin D3 synthesis - failure to provide correct UV-B is a major and preventable welfare problem in both zoo and private keeping.
UV-B deficiency in reptiles causes progressive metabolic bone disease - painful skeletal deformity, pathological fractures, muscle weakness, and impaired organ function. This is a major and historically widespread welfare failure in reptile keeping. The Ferguson Zone system for classifying species UV-B requirements and the availability of calibrated measurement tools have transformed best practice. Zoos and private keepers who provide correct UV-B gradients prevent significant chronic suffering. Educational outreach on UV-B requirements is a key animal welfare intervention.