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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 one of several common names for metabolic bone disease (MBD). It is caused by a poor quality or imbalanced diet. It occurs most often in young, growing chicks (where it is referred to as 'rickets'), and older hens (where it is known as 'cage layer fatigue').

Clinical Signs

Chickens with avian osteoporosis may find it difficult to walk, and as such, as very reluctant to move. Their legs may appear slightly deformed and distorted, often developing valgus deformities. They are also very susceptible to bone fractures.

Avian osteoporosis is a severe welfare concern in commercial laying hens, especially those that are kept confined in tiny cages their entire lives. In the United Kingdom, recent studies showed that 29% of laying hens had at least one broken bone. Osteoporosis, named after the latin equivalent for "porous bones", which results in decreased bone strength and density. This causes the bones to weaken. Once they are weakened, it doesn't take much for them to break---even jumping down from a roosting perch could potentially break the leg of a hen with osteoporosis.

The reason hens are particularly susceptible to osteoporosis is related to egg laying---thus hens with "high egg production" rates are thus more prone to this disease. Every time a hen lays an egg, it depletes her body (including bones) of important minerals, with one of the most significant being calcium. Bone mineral loss begins when hens reach sexual maturity, and continues throughout their life span as long as they lay eggs. The increased egg laying demands on modern hens, requires a proportional increase in the amount of calcium in the diet. This is because the major component of eggshells is calcium carbonate. Calcium is important for the formation of the egg shell as well as the quality and thickness of the shell. If hens are not provided enough calcium to meet the high demands required for egg laying, the calcium is taken from their bones. The condition can be made worse by metabolic deficiencies related other nutrients as well---such as inadequate or unbalanced quantities of phosphorus or vitamin D in the diet.

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
  • Diet is lacking in Vitamin D
  • Excessive egg laying
  • Birds with liver or chronic kidney disease
  • Receiving steroids