Calcium is not only necessary for bone and egg formation but also for normal cellular physiology. This is important to remember: All muscle contractions including those of the heart are dependent on normal levels of calcium in the body. Calcium comes in two basic forms water soluble (bicarbonate) and carbonate. The water soluble (bocarbonate) forms are mostly found in fruits and vegetables. This calcium is readily absorbed and used. The carbonated form is mostly found in things like eggshell, cuttlebone and grit. Unfortunately, this carbonated form of calcium although abundant and inexpensive, is not easily assimilated. Most of that calcium that a bird consumes goes straight through the gut, out the tailpipe and onto the cage floor. To speak of it in a more dignified way, the intestines do not readily absorb carbonated calcium very well. Incidentally, stress and inactivity (small cages) also deplete calcium levels in the body. Vitamin D3 is necessary for the bird to absorb calcium. Vitamin D3 must be converted over a two day process in the liver and kidneys to ultimately form a calcium binding protein. Therefore normal liver and kidney function are also necessary for the proper absorption of calcium. The rate of calcium absorption is directly proportional to the quantity of this calcium binding protein in the intestinal cells.

Of interest to bird breeders is exchangeable calcium. This is calcium salt deposited in bones which can readily enter the blood stream in times of need, such as egg laying. A hen cannot physically ingest enough calcium in a 24 hour period to compensate for the formation of an eggshell. Therefore her body must pull calcium reserves from her bones & tissue. If her body is already low in calcium, her muscles will not be able to respond, i.e. she will not be able to fly, and will "eggbind." In humans low calcium levels causes cramping and a failure of muscle function. That's why you find eggbound hens sitting in the bottom of the cage. They cannot fly. The hen will also be in a highly stressed condition. However, the term "eggbinding" is something of a misnomer. The truth is, the egg is just sitting there, but the hen does not have the ability to contract her muscles and expel it (no small task in itself). A dose of absorbable liquid calcium will bring almost immediate results.

The need for good levels of calcium in the body is why it is critical to only breed mature hens in good condition and to feed and exercise them properly several months prior to breeding. Immature and poorly conditioned hens will not have adequate body calcium reserves resulting in hypocalcemia (low blood levels of calcium), i.e. eggbinding.

I mentioned that some dark, leafy greens interfere with the absorption of calcium. In "Calcium in Cage Bird Nutrition" Robert Black writes "Another acid that goes by the name of oxalic acid is found in spinach, beet greens, chard, and rhubarb. Oxalic acid in the digestive tract combines with calcium to form a compound called calcium oxalate. The body cannot absorb this compound through the intestinal walls, and it passes through the digestive system and is excreted. Any breeder who regularly feeds any of these vegetables to the birds is likely to note calcium problems in the flock."

Dark leafy greens are such good sources of nutrition it is difficult to recommend that you not feed oxalated ones to your birds. But, if you chose to, it is important that you not overfeed them, because you will create problems. What's too much? That is the dilemma. The amount of oxalate in a plant varies considerably on growing conditions and whether it is raw or cooked (cooked foods are higher). My choice is to avoid these greens (spinach, chard, beet greens, parsley and rhubarb (which is toxic anyway) because there are acceptable substitutes available such as dandelion, collard greens, turnip greens, mustard greens, chicory, broccoli, egg shells, cuttlebone, mineral block, brewer's yeast, oats and kelp. If you are looking for a upplement beside good diet, the best calcium to look for is calcium/magnesium liquid. This means it is water soluble. Also look for a supplement that contains calcium lactate, gluconate and citrate because it wil be even more absorbable.

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Cross-posted with permission from Bird_Breeder-Hobbyist Mailing List

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