Osteoporosis is a common health problem for laying hens, especially those confined in industrial battery cages or open-floor sheds. Bone weakening and breakage, including but not limited to the keel bone, can be extremely painful and even fatal. Studies have shown as many as 97% of tested hens experienced keel breakage.
While a diet with supplemental calcium and other minerals can affect bone density, by making calcium available for uptake from the intestinal lining, the timing of hens’ egg-formation cycle means that their bones remain a key source of calcium for egg shell formation. Some studies have shown upwards of 40% of shell calcium coming from medullary bone.
Modern laying hens lay between 200-300 eggs per year. But they are the descendants of wild red junglefowl, who lay 10-15 eggs per year in 1-2 clutches. The prevalence of osteoporosis in industrial laying hens despite formulated feeds points to a startling reality: selective breeding has forced hens to lay harmful numbers of eggs, causing dangerous depletion of their bodies’ skeletal system and overall minerals that they need for good health.
Caregivers at vegan sanctuaries have seen firsthand the reality of osteoporosis in laying hens, through treatment of injury and diagnostic imaging. Cessation of egg laying through hormonal intervention, or naturally with age, leads to improvement in bone density.
The direct connection between laying rates and osteoporosis means that every egg contributes to dangerous, potentially fatal health conditions in laying hens.
There is no such thing as an ethical egg.
Sources
“Avian Skeletal System”:
https://poultry.extension.org/articles/poultry-anatomy/avian-skeletal-system/
“Calcium and Cholecalciferol Levels in Late-Phase Laying Hens: Effects on Productive Traits, Egg Quality, Blood Biochemistry, and Immune Responses”:
https://pmc.ncbi.nlm.nih.gov/articles/PMC7412964/
“Physiological regulation of calcium and phosphorus utilization in laying hens”:
https://pmc.ncbi.nlm.nih.gov/articles/PMC9942826/
“The Influence of Keel Bone Damage on Welfare of Laying Hens”:
https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2018.00006/full
“Reduced bone breakage and increased bone strength in free range laying hens fed omega-3 polyunsaturated fatty acid supplemented diets”:
https://pubmed.ncbi.nlm.nih.gov/23142806/
“Welfare implications of avian osteoporosis”:
https://pubmed.ncbi.nlm.nih.gov/14979568/