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Metabolic bone disease is the weakening or softening of the bones which can be caused by a number of disorders, including nutritional secondary hyperparathyroidism. When there is an imbalance in the calcium and phosphorous levels in a bird’s system it is frequently caused by a deficiency in the calcium level included in the animal’s daily diet. This can lead to broken and deformed bones, a reduction in mobility, and if unaddressed for long enough, it can even lead to the animal’s ultimate demise.
Hyperparathyroidism is a deficiency in the metabolism of calcium absorption that can lead to progressively distorted bone growth, fractures, and in some cases, seizures.
This disorder is more commonly seen in younger birds due to the larger stores of calcium required for growing bones and is not does not discriminate based on gender or breed.
Nutritional secondary hyperparathyroidism is rare in wild bird populations but occurs slightly more often in animals cared for by humans. Common mistakes made by avian caretakers that can lead to Nutritional secondary hyperparathyroidism can include:
Birds of Prey - Birds of prey that are fed only meat without any bones may develop calcium deficiencies, while those that eat whole prey animals get higher calcium levels from ingesting the bones
Parrots - Parrots that are fed an all seed diet are at an increased risk of developing this disorder as well as iodine deficiency, infections, and abscesses; some psittacines, such as the African Grey, can be prone to Vitamin D deficiency
Although genetic disorders may be implicated in the development of metabolic bone disease is more often caused by an improper diet and environment.
Dietary - Although calcium deficiencies in the diet frequently trigger this disorder, an overabundance of phosphorus which binds to the calcium can also cause an imbalance, preventing the absorption of the calcium
Chronic egg laying can also cause a comparable drop in calcium and may result in the same symptoms of nutritional secondary hyperparathyroidism.
There are several factors in the veterinary examination for birds that will help to diagnose this disorder. The biochemistry profile that is performed on the blood serum may show decreases in the calcium levels or increases in the levels of phosphorous, as well as revealing imbalances in the enzymes that are used to evaluate liver and kidney health. Direct examination of the fecal material, fecal gram stains, and cultured samples may assist in ruling out the involvement of parasites or infections as a cause of the symptoms.
X-ray imaging is particularly important in cases of metabolic bone disease as it can help to identify if any fractures or swelling of the joints are present as well as visualizing any decreased bone density or warping that may have occurred due to softening, and ultrasound technology can give the examiner a clear picture of the size and positioning of the organs. Many birds will require sedation to get clear enough images for diagnostic purposes.
Initial treatment generally includes the administration by injections of calcium glubionate or calcium gluconate to help normalize blood calcium levels. Corticosteroids are typically avoided as a treatment for calcium deficient animals as it can further impede calcium absorption and excretion by the kidneys, however, Vitamin D supplementation can be useful in facilitating the transfer of the calcium from the digestive system into the bloodstream. Any bones that are fractured or deformed will need to be addressed. Internal fixation methods for stabilizing the bone which includes the insertion of pins and wires are frequently unsuccessful for birds with this disorder due to the weakening of the bone.
External splints and cage rest are more frequently used to guide healing and can be quite successful, although some birds require NSAIDS to reduce pain and swelling. Changing the bird’s diet to include more calcium is essential for the successful treatment of this disorder; your companion bird’s diet will need to include more varied food options or a change to a nutritionally complete pellet diet will be required and adding prey animals with the bones to the raptor diet will help to increase the calcium available to heal and strengthen the bones. Birds that are being treated for this disorder will require multiple x-rays to monitor the healing process of the bones.
The prognosis for birds that have developed metabolic bone disease due to dietary deficiencies depends on how much damage has occurred before treatment is begun. In situations where the bones are weakened but without fractures or deformities, the chances of full recovery are good. Birds that have developed distortions or stress fractures may still recover, but the healing time will be extended, and some defects may be permanent. Serious malformations of the bone and complex fractures have a more guarded prognosis. In especially severe cases, the decreased mobility impacts the patient's quality of life to the point where euthanasia is recommended.
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