Calcium Metabolism in Birds
by Dr Susan Orosz

Susan E. Orosz, Ph.D., D.V.M., Diplomate ABVP, Avian Practice, Diplomate, European College of Avian Medicine and Surgery, Professor. Dr. Orosz is a Professor at the University of Tennessee, Knoxville, specializing in Avian Medicine

Calcium is an important mineral for birds, serving as a structural component of bones and shells and as a “messenger” between cells that allows them to respond to hormones and have normal nerve function. It is also important for normal blood clotting. The level of calcium in the blood is kept steady in healthy birds by a complex process involving several organs including the kidney, the gastrointestinal tract, and bones.

Calcium exists in different forms within the body-as free ions circulating through the blood, a protein-bound form, and a “chelated” state. The body monitors the free ion concentration, making corrections whenever it gets too high or too low.

Birds get calcium from their diet, and the quantity and form of the calcium matters. Calcium absorption in the gut is affected by the calcium status of the bird, how much vitamin D is present, the age of the bird, and whether it is laying eggs. Calcium absorption in the gut is also affected by the bird’s exposure to ultraviolet light or direct sunshine. Light is used by the body to convert a form of vitamin D made naturally by the bird’s body into a usable form, vitamin D3. This active form is used by the bird to absorb calcium along the gut. Without sunlight, vitamin D3 must be obtained from the diet.

The amounts of zinc, manganese, and other positively charged metals in the diet also affect calcium absorption, because these metals act similarly to calcium. The amount of phosphorous in the diet influences calcium absorption. A type of plant protein called phytate can interfere with calcium uptake, along with certain fibers.

Different birds need different amounts of calcium in their diet. For example, some species like budgerigars appear to need less calcium than others, while others like African grey parrots probably need more. The actual values for birds in general are not well known. Birds that are growing or laying eggs generally will need more dietary calcium than those that are mature or not laying.

Too much calcium in a bird is a problem, and so it too little.

If birds get too much calcium, the calcium can mineralize the kidney, forming hard calcium deposits, and possibly lead to death. The birds may also be lame.

If birds get too little calcium, the bird may show decreased growth, decreased appetite, suffer convulsions, and break bones easily. The beak may get soft and blood may have difficulty clotting. Eggshells may be fragile. Chicks would be especially vulnerable.

A recent article in a trade publication reported research suggesting that calcium levels should be between 0.3 and 0.7% for budgerigars, which are also known as budgies or parakeets. These recommendations represent preliminary findings from an unpublished study. This research may be significant, because dietary calcium requirements are not well known, but it is important to see the data published in a refereed journal article. Other scientists in nutrition will need to go over the study to determine if it was done properly and if it considers other factors besides calcium alone. For example, the amount of vitamin D is especially important in calcium absorption.

The ability of a diet to keep birds healthy overall is what really matters. In 25 years of experience, Nutriberries or pellets as 70% of the diet, along with high vitamin A foods, have performed well for bird owners. Lafeber pellets with Nutriberries have been used as the exclusive diet for 20 Amazon parrots at the Research Facility at The University of Tennessee College of Veterinary Medicine since 1994. Blood values and various tests have not shown any problems with the diet. Budgerigars were also fed the Lafeber pellet/Nutriberry combination for 1 year without any problems noted.

It is remarkable that birds are generally able to maintain calcium balance with varying demands based on body processes (laying eggs, growing, etc). Controlled levels of calcium and vitamin D, such as those found in Lafeber products, provide one way to ensure a consistent and balanced dietary supply.