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Avian Osteoporosis

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

Avian osteoporosis is a metabolic bone disease (MBD) that occurs commonly in laying hens, in which 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. Heat stress can also make the condition worse because it has an effect on the levels of circulating ionic calcium in her blood.

Clinical Signs of Avian Osteoporosis

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

Reluctance to move
Fragile bones that easily fracture


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


CalciumGiven by injection or orally
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 any secondary complicationsSuch as bone fracture and deformities.
DietThe 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.



  • Ensure laying hens receive a balanced diet with extra calcium. Feeding calcium in particulates, either as oyster shell or limestone granules, may extend the period of calcium absorption during the night, which reduces the depletion of medullary bone and benefits the eggshell quality
  • Allow hens plenty of exercise
  • Oral supplementation with 20 mg/kg of ipriflavone in feed
  • Provide supplemental Omega 3 Fatty Acids in diet - Studies showed a significant 40 to 60% reduction in keel bone breakage rate, and a corresponding reduction in breakage severity.


Scientific References

Age Range

It is most common in young growing birds or older hens.

Risk Factors

  • Getting fed a diet with a negative calcium to phosphorus ratio
  • Little to no sunlight exposure
  • Low or high levels of phosphorus in the diet.
  • Vitamin D deficiency
  • Excessive egg laying
  • Birds with liver or chronic kidney disease
  • Receiving steroids
  • Heat stress
  • Feeding low quality feed
  • Errors in feed formation at feed mills