A Compassion Over Killing Report:
Animal Suffering in the Egg Industry
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)
