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Calcium is one of the most important nutrients required by the avian species, not only for its obvious structural functions such as bone development and eggshell formation, but also for its importance in cellular regulation.

Dietary calcium is typically supplemented as calcium carbonate since most dietary grains are very limited in their calcium content. Calcium carbonate varies in its availability to the bird depending on its particle size and solubility.

The companion bird requires a fairly small particle size with maximum solubility. Most of the calcium is solubulized by HCl secretions in the bird’s proventriculus and gizzard.  A healthy gizzard is very important  and can be enhanced in birds by the inclusion of some coarse dietary fiber.

After solubilization of the calcium in the gizzard,  is actively transported by vitamin D calcium binding protein in the duodenal loop of the small intestine. Vitamin D is extremely important here and should always be supplemented in a complete companion bird ration.

Kidney health and function are also important for calcium absorption because the final hydroxylation of vitamin D to 1,25 dihydroxycholecalciferol takes place in the kidney.

Any disease or virus that may have altered kidney function can negatively affect calcium metabolism. Excessive calcium feeding can also stress the kidney in birds, causing a gout condition.

Fortunately, recent research has shown that the large intestine may also play an important role in calcium metabolism. Research at UNL has indicated a very well developed capacity for the chicken to passively transport calcium in the large intestine. This type of passive transport would be non - vitamin D dependent and actually enhanced by the presence of soluble dietary fiber (such as oat groats).

This is promising research since many conditions can mar vitamin D function in older birds.

The large intestine has been overlooked in nutrient absorption, but could become an important tissue if birds have a small intestine disease such as coccidiosis or enteritis.

Research will continue to be conducted at UNL to look at the function of fiber to enhance large intestine absorption in avian species. Calcium metabolism may also play an important role in the condition of profuse egg laying cockatiels.

It is well known that in laying chickens, the best way to stop egg production is to drastically lower the dietary and serum calcium. The lowered serum calcium sends a signal to the ovaries to stop ovulating.

It may be that profuse egg layingin cockatiels is enhanced by too much dietary calcium and that a calcium restriction could help take these birds out of egg production. Most birds have plenty of skeletal reserves to produce a small clutch of eggs (4-6) without supplementing calcium. There remains the possibility of an endocrine malfunction in profuse laying cockatiels, but this too could be affected by serum calcium levels.

Sheila E. Scheidler, PhD
University of Nebraska, Lincoln

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