Calcium is a mineral required by all animals as an essential part of their diet, along with other elements such as Phosphorus, Magnesium, Potassium, Sodium, Iron, etc. Disease conditions caused by a deficiency of calcium (or more usually an imbalance of calcium and phosphorus, together with a lack of vitamin D) are very common in captive parrots. 

Calcium compounds are familiar in nature as relatively hard minerals such as chalk, limestone, cuttlefish bone, eggshells and oyster shell. Perhaps the most recognised manifestations of the mineral in the body are its incorporation in the structure of the bony skeleton and in the production of eggshells, but it also has an important unseen function in solution in the bloodstream in the proper contraction of muscles. 

Bone and shell structure depend on a proper combination of calcium and phosphorus in the right ratio; and the uptake and assimilation of calcium is also linked to the availability of vitamin D₃. If a bird has insufficient calcium available, then the signs seen can be many and variable, depending on the bird’s age and sex, and the degree of the deficiency. A low blood calcium level (measured by taking blood samples from a vein) is known as HYPOCALCAEMIA. The reverse – too much calcium – would be hypercalcaemia. 

Hypocalcaemia occurring in an adult breeding hen may first produce infertility, in that the hen is unable to develop eggs at all. If she does produce eggs, these may be soft-shelled, which makes them difficult to lay, and unlikely to survive. The next stage would be egg-binding, when an egg becomes stuck in the oviduct. This is a common problem, and may also be the result of immaturity of the bird, debility after laying eggs, or a change to cold and damp weather conditions after fine weather. However, as mentioned previously, Calcium is essential for proper muscle contraction, and a mild deficiency will mean that the oviduct cannot contract properly to expel the egg. 

The treatment of egg-binding includes the provision of heat to the bird; encouraging fluid intake by adding honey or glucose to the water; lubrication of the vent; and the administration of calcium. Vets usually give an injection of calcium solution, together with Oxytocin, the hormone that aids in giving birth. The calcium has to be injected or rapidly absorbed orally – it is no good giving cuttlefish bone at this stage, as the calcium takes too long to extract and metabolise. 

An egg-laying hen has a tremendous demand for calcium, and if this is not supplied in the diet, then reserves laid down in her bones will be withdrawn to go to egg production. This will result in brittleness of the bones showing as stiffness or weakness, and the possibility of bone fractures. 

Provided enough calcium has been available successfully to produce an egg which subsequently hatches, then the next stage for hypocalcaemia to strike is in the developing chick. The chick’s early nourishment depends upon nutrients contained in the yolk sac, and subsequently that provided by the parents, and if the hen has inadequate calcium reserves then the chick also will not receive enough. Its growth will be slow and stunted, and the usual effect is that the growing bones are soft and poorly mineralised. As the chick gets heavier, the long bones of the legs and wings bend under the strain – so-called “rickets”, better described as Metabolic Bone Disease. 

Such a condition will occur in a hand-reared chick, even if the rearing food contains sufficient calcium. This is because it takes a while for the chick to assimilate the mineral from its food, and meanwhile the rapid growth rate coupled with the poor supply from the yolk will still produce bone deformities. Treatment involves proper supplementation thereafter, but once curvature has occurred the bone will not straighten again by itself. It may be necessary surgically to break and reset the bent limb, but this requires avian orthopaedic expertise and intervention at the right time. 

Finally, in a non-breeding adult bird, there is another common manifestation of hypocalcaemia in the form of nervous signs. These can occur in any species, but most frequently are encountered in Eclectus Parrots and African Greys. Grey Parrots appear to have a particularly high demand for calcium, or perhaps they have more difficulty than other birds in metabolising what is available. As mentioned before, calcium is required for proper muscle function, and when blood levels are low, we see signs ranging from slight weakness making it difficult for the bird to move round its cage; progressing through more marked inco-ordination and loss of balance; and culminating in fits or seizures of an epileptic nature. 

The usual reason for the occurrence of hypocalcaemia is a chronic deficiency in the dietary intake. Classically, the condition is seen in parrots eating a diet just of sunflower seeds and peanuts. African Greys particularly can become addicted to sunflower seed, and can be very difficult to persuade to eat alternatives. Calcium-rich foods include the dark greens such as broccoli, spinach, kale and the like; plus dairy products such as cheese, milk and yoghurt. Calcium is usually offered to birds in the form of cuttlefish bone, mineral blocks, or oystershell grit, but these products have some disadvantages. Many birds will not touch them, or if they do, tend just to destroy the substance without eating it. Even if it is ingested, the calcium available is poorly digested – perhaps only 2% of that taken in is absorbed into the bloodstream. 

The calcium in dairy products is much more efficiently utilised, and milk (skimmed or semi-skimmed) can be a useful emergency supply. The disadvantage is that the fat content and lactose sugar are not easily digested, so long-term administration of milk may result in diarrhoea. 

Various powdered vitamin and mineral supplements (SA37, Vionate, Nutrobal) are available, but these are only effective if they can be given in moist or sticky food that the bird will eat. The powder will drop through dry seed, unless it is coated with oil. Most, with the exception of Nutrobal, are intended for dogs and cats and do not contain sufficient calcium to help an African Grey, especially with acute hypocalcaemia. Soluble calcium supplements administered in the drinking water are perhaps more immediately beneficial – human proprietary tablets are available from the chemist, or there are avian–specific products such as Calcivet or Zolcal-D. Always remember that calcium given orally will block the absorption of Tetracycline antibiotics, so the two drugs should not be used together. 

In an acute case of seizures or egg-binding, the only satisfactory treatment is the administration of calcium by injection, in which case the results obtained are usually rapid and dramatic. 

Owners and breeders need to be more aware of the prevalence of this condition, and its prevention by the provision of an adequate diet or of calcium-rich supplements. 

© Alan K Jones 1993/updated 2005.