Laying hens are uniquely susceptible to osteoporosis because the physiological demands of egg production deplete structural bone calcium, causing fragility fractures that represent a major welfare problem across all housing systems.
Osteoporosis and fracture in laying hens represents a structural welfare failure embedded in the physiology of high-production commercial breeds. The calcium demands of egg production systematically weaken bone over the laying cycle in ways that cause pain and limit mobility. Hens cannot signal injury in ways that humans readily recognise, meaning fracture pain is largely silent and unaddressed at the population level. The tragedy is that fracture prevalence has actually increased with cage-free transitions in some systems, because poor perch design leads to collision injuries that offset the benefits of increased movement. Welfare improvement requires a combination of better perch design, fracture-resistant breed selection, and end-of-lay management that accounts for the extremely high fracture burden in birds at this stage of their lives.