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Avian Osteoporosis

Other Names: Cage Layer Fatigue, Brittle Bone Disease, Metabolic Bone Disease, Nutritional Secondary Hyperparathyroidism, Fibrous Osteodystrophy, Osteomalacia, Rickets

Avian osteoporosis is a metabolic bone disease (MBD) and orthopedic condition which occurs commonly in commercial laying hens. It is often referred to as 'cage layer fatigue'. The reason hens are particularly susceptible to osteoporosis is related to egg laying. The formation of the eggshells require large amounts of calcium. If hens do not receive enough calcium in their diet, each time they lay an egg, calcium will be depleted from their bones instead. The condition can be made worse by metabolic deficiencies related to other nutrients as well---such as inadequate or unbalanced quantities of phosphorus or vitamin D in the diet.

Avian osteoporosis occurs more frequently during the summer, because heat stress has a negative effect on the amount of circulating ionic calcium in the hen's bloodstream.

Clinical Signs

Chickens (usually hens) with avian osteoporosis have really fragile bones. Many of these birds may find it difficult to walk, and as such, are very reluctant to move. Their legs may appear slightly deformed and distorted. Others may develop sudden paralysis. These birds are at high risk of bone fractures, with the most common being their keel and leg bones.

Clinical Signs

Inability to stand
Soft, thin or shell-less eggs
Not laying eggs


  • History
  • Diet evaluation
  • Physical exam
  • Radiographs - Decreased bone density, deformities, or fractures
  • Serum Calcium - May have decreased levels in blood


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Calcium carbonateAdminister 1 g orally, daily for one week.
Calcitonin-salmon (Calcimar, Miacalcin)Can actually reverse the effects quickly, however because it pulls the calcium out of the bloodstream, the bird must first be given calcium and vitamin D3. This drug can be fatal if it is given incorrectly and therefore should only be administered by a vet who has had prior experience using the drug before.
Supportive careSince affected chickens are very susceptible to bone fractures, they need to be handled very carefully and kept protected from potential injury.
Treatment of secondary complicationsSuch as bone fracture and deformities.
Diet changeThe chicken's feed needs to be evaluated and corrected accordingly, in order to ensure they are getting the proper balance of vitamins and minerals in their diet.



  • Feed laying hens a properly balanced laying or breeding feed.
  • Provide free access to large-particle oyster shell or limestone granules.
  • Allow hens plenty of exercise outdoors.


Scientific References

Age Range

It is most common in older hens.

Risk Factors

  • Feeding hens an unbalanced diet or feed intended for other stage of growth which results in a diet low in calcium, phosphorus, or vitamin D.
  • High-producing egg laying breeds
  • Hens with existing liver or kidney problems.
  • Receiving steroids
  • Heat stress