A COK Report:
Animal Suffering in the Egg Industry

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Bone Weakness

Battery hens are typically kept inside environment-controlled houses and never see sunlight. Vitamin D is necessary for the absorption of calcium, and its production is triggered by sunlight.(31) Although hens are fed supplementary vitamin D, many still suffer from osteoporosis. Much of the hens' calcium is used to produce the shells of their eggs, thereby reducing the amount of calcium available for bone maintenance. Bone weakness is exacerbated by the hens' lack of exercise in battery cages.(32) One study found that 89 percent of laying hens suffered from osteoporosis.(33) It is estimated that even before capture and transport, one in six hens suffer from broken bones.(34) Dr. Baxter states that "hens are restricted from exercising to such an extent that they are unable to maintain the strength of their bones. The increased incidence of bone breakage which results is a serious welfare insult."(35) Research has shown that the type of housing, such as aviary, perchery, or enriched cage, also has an influence on bone strength.(36) Dr.A.B. Webster concludes that "those housing systems that foster the greatest physical activity produce hens with the strongest bones."(37)

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