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The Importance of Calcium In Your Grey's Diet
Alicia McWatters, Ph.D., C.N.C. © 1997
Calcium deficiencies, in African Greys, are a common concern for many aviculturists. The following discussion will include details about the vitamins and the minerals most closely associated with calcium. Nutrient deficiencies, as well as toxicities, will also be addressed.
Calcium is the most abundant mineral in your bird's body. The major function of calcium is to work in conjunction with magnesium and phosphorus for building and maintaining strong bones and in the metabolism of vitamin D. Calcium also aids in enzyme function, fat metabolism, egg-shell formation, nerve transmission, hormonal secretion, blood clotting, muscle growth and contraction, helps maintain a healthy heart and facilitates the passage of nutrients in and out of the cell walls.
The ratio of calcium to phosphorus in the bones is approximately 2.5:1, so it is important to try to maintain this level in your bird's diet. To function properly, calcium must be accompanied by magnesium, phosphorus, and vitamins A, D3, and C. Calcium absorption is very inefficient and only a small percentage of what is ingested is actually absorbed, and much of what is ingested is excreted in the feces.
Certain foods, while rich in calcium, contain calcium binding substances
called oxalates (salts of oxalic acid), and are found in spinach, beet
greens, chard, kale, soybeans, and almonds, for example. When oxalates
are combined with calcium it makes an insoluble compound and inhibits the
absorption of calcium and other important minerals in
the intestine.
Phytate (salt of phytic acid) compounds are present in dry, dormant seeds, pulses, and grains, and if served in large amounts may also inhibit the absorption of calcium. Therefore, these foods should be offered in limited amounts. If the excessive feeding of foods containing oxalates, phytates, phosphate, magnesium, protein, or fat occurs, it may cause hypocalcemia (an abnormally low level of calcium in the blood). A low level of calcium, magnesium, or vitamin D, can also create this problem and drugs, such as tetracycline, sugar, stress, and inactivity can deplete calcium in your bird's body.
Symptoms of hypocalcemia are seizures, heart disorders, elevated blood cholesterol, soft-shelled eggs, bone disorders, nervousness, and tetany. Tetany is defined as a condition where severe intermittent tonic contractions and muscular pain occurs, due to the abnormal metabolism of calcium. On the other hand, a high intake of calcium and vitamin D is a potential source of hypercalcemia (an abnormally large amount of calcium in the blood). This may result in excessive calcification of the bones and some tissues, such as the kidneys or heart.
Calcinosis is an abnormal condition in which calcium salts are deposited in a tissue of the body. It may also encourage loss of calcium from bone. The parathyroid glands are responsible for regulating homeostasis of blood calcium and phosphate. Calcitonin is a hormone produced by the thyroid gland and it helps to maintain homeostasis of blood calcium and functions to prevent excess calcium in the blood.
Greys are more likely to develop hypocalcemia and tetany than hypercalcemia, because of their special requirement for calcium, magnesium, and vitamin D. Many foods provide calcium and there is little chance of an overdose by your food supply. But, it is important to regulate the amount of calcium supplied in your bird's diet in the form of a supplement; this includes any commercial synthetic feed you may be feeding your Grey.
Very often, with good intentions, aviculturists may be over supplementing their birds with certain vitamins and minerals, while others may not be offering adequate quantities in their bird's diet, therefore an additional supplement is necessary. There are several types of calcium supplements on the market but not all of them are created equal. Bone meal can be used as a calcium supplement for our Greys. While it contains a high calcium concentration and is the most affordable type of calcium, it can be difficult to assimilate and may also contain lead residues. However, there are some bone meal supplements which have been lead-tested and are guaranteed to contain negligible levels of lead.
As an alternative to bone meal, we use Calcium Magnesium Liquid (1/2
tsp. per day for Greys). CML, with its proper ratios, is made from calcium
lactate, citrate, and gluconate and contains no preservatives, sugar or
milk. CML contains a much lower concentration of calcium than bone meal,
so more is required, but it is readily absorbed from the intestinal tract.
A good way to test your present (powdered) calcium supplement for its
absorption quality, is to place 1/4 teaspoon in a 6 ounce glass of
white vinegar. Stir every 5 minutes for 30 minutes. If the calcium has
not dissolved, change to another brand.
Various foods are rich in calcium and can be included in your Grey's diet, such as green leafy vegetables (e.g., collards or mustard greens), almonds, oranges, brewer's yeast, buttermilk, cheese, yogurt, oats, kelp, cooked beans and peas, sunflower and sesame seeds.
There are herbs which are known to be high in calcium (e.g., dandelion, parsley, comfrey, alfalfa, horsetail, oat straw, and chamomile). Many of these can be served fresh, dried, or sprinkled over fresh food by capsule powder. Vitamin D "the sunshine vitamin", is known to be an immunity enhancer. Provitamins D are found in both plant and animal tissue.
In the plant form, ergocalciferol is classified as vitamin D2, and is known as calciferol; vitamin D3 or cholecalciferol, is the natural form as it occurs in fish oils. Vitamin D2 is produced by irradiation with ultraviolet light of ergosterol in plant sources such as yeast or fungi and vitamin D3 is synthesized by the action of ultraviolet light on 7-dehydrocholesterol in the skin.
Vitamin D is not immediately activated, but requires enzyme conversion
by the liver into
25-hydroxycholecalciferol, and then by the kidney into the active form,
1,25-dihydroxycholecalciferol before it becomes fully utilized. Full spectrum
lighting (Vita-lights or OTT lights) can be useful as an artificial substitute
for the natural ultraviolet light from sunlight.
The active form of vitamin D is manufactured in response to the secretion of the parathyroid hormone, which helps to increase the uptake of calcium when blood calcium levels are low. Those birds who have a kidney or liver disorder may not be able to convert vitamin D to the active form. Vitamin D is important for the absorption of calcium from the intestine, and in the breakdown and assimilation of phosphorus, for the normal depositing of these minerals into bones, for normal growth and development. This fat-soluble vitamin in conjunction with calcium is valuable in maintaining a stable nervous system, normal heart action, and normal blood-clotting.
All fat-soluble vitamins, require at least a small amount of fat in the diet, along with the secretion of bile acids for absorption to take place, for it is not readily excreted, and is stored in the liver, skin, brain, bones, and other tissues. Vitamin D is best utilized when taken with vitamin A for a boost to the immune system. These two vitamins taken along with vitamin C act as a preventive measure against infection and also increase the absorption of calcium.
Food sources include fish-liver oil, egg yolk, and sunflower seeds to name a few. Fish liver oils are the best source of vitamins A and D. The liquid calcium we use contains fish- liver oil as its vitamin D3 source. Phosphorus is the second most abundant mineral in your bird's body and is found in every cell. It functions with calcium and is necessary for these minerals to be effectively utilized by the body. It is important for RNA/DNA synthesis, nerve health, heart/muscle contraction, kidney function, and the utilization of carbohydrates, proteins, and fats, and for the growth, maintenance, and repair of cells and for the production of energy. The ratio should be approximately half that of calcium and equal to magnesium.
Factors which inhibit phosphorus absorption are an excess of refined sugar, iron, and magnesium, and insufficient vitamin D and calcium. Food sources include garlic, eggs, brewer's yeast, legumes, grains, seeds and nuts. Magnesium is located in the bones with calcium and phosphorus and in the soft tissues and body fluids. It is involved with many metabolic processes. It also helps regulate the acid-alkaline balance in the body. It helps utilize the B-complex, vitamin C, E, and promotes absorption and metabolism of other minerals, such as, calcium, phosphorus, sodium, and potassium.
The proper ratio of vitamin D is necessary for proper metabolism of magnesium. The ratio of calcium to phosphorus and calcium to magnesium is important in the absorption, use, and excretion of these minerals. Magnesium should be in an equal amount to phosphorus, and both should be half that to calcium.
Some factors which inhibit absorption of magnesium are stress, sugar, and tetracyclines. Food sources include whole grains, dark-green vegetables, corn, apples, legumes, seeds and nuts, especially almonds. Raw foods contain this mineral in abundance, while the cooking of foods removes it.
African Greys have great density to their bones. If you hold or perch even a very young Grey on your hands you will notice the heaviness of its body. When handfeeding a young Grey you will observe the strength of their pumping action when eating. I believe it is because of this density that our Greys require an additional amount of calcium and therefore their nutritional needs are somewhat different.
Those Greys on an inadequate diet are often deficient, at least marginally, in calcium and other minerals and vitamins causing symptoms of a minor degree, which usually go unnoticed. With the occasional overdosed bird creating toxicity. Either way, nutritional deficiencies or toxicities develop in stages over the long-term and are not always recognizable in the early stages. Eventually visual detection is observed beginning with various abnormal behavioral changes. Clinical signs may take place to call it to your attention that nutritional or medical attention is required.
Some of the following problems may occur if vitamin D, calcium, phosphorus, and magnesium are not provided in the proper balance. A deficiency in calcium would result in low blood calcium and the drawing of mineral from bone leading to the reduction in bone density in adult Greys and rickets in growing youngsters. Calcium is required for normal nerve transmission. The nerves become hypersensitive when blood calcium levels drop below normal and tetany (painful spasms of the muscles) can result. Also, normal muscle tone relies on the proper balance between calcium, sodium, potassium, and magnesium.
Also, review symptoms of hypocalcemia on first page. A vitamin D deficiency would cause similar symptoms to a calcium deficiency. The symptoms of vitamin D overdose or "hypervitaminosis D," can include diarrhea, weakness, itchy dry skin, loss of appetite, calcium deposits in soft tissue, irreversible kidney or heart damage, or retarded growth. Vitamin D overdose develops over time and there is a wide variation among individual birds in their tolerance to toxicity. Young growing birds are more susceptible than older birds to vitamin D toxicity.
With phosphorus we often find it is more common to be oversupplied with this mineral than for a deficiency to occur. However, a deficiency may cause weight problems, joint stiffness, weakness, trembling, and appetite loss. If your bird's diet contains excess phosphorus, this would inhibit the uptake of calcium. A deficiency in magnesium can develop if not supplied in your Grey's diet.
Insufficient intake affects all tissues, particularly the heart, nerves and kidney. These would include loss of appetite, growth failure, lack of coordination, GIT disorders, hypertension, or depression. In addition weakness, muscle tremors, weight loss, nervousness, and feather loss may result. Again, this is usually the result of a poor diet, as magnesium is refined out of many foods during cooking/processing.
Toxicity is rare, but would cause weakness, sleepiness, and breathing difficulties. If any of the above signs are noticed in your bird it would be of value to have the blood levels checked for the vitamins and the minerals described. The most important thing to remember is that the function of calcium, magnesium, phosphorus, and vitamin D, in their proper ratios, are all closely dependent on one another. This is particularly vital in birds that are breeding/laying and raising young.
If you are handfeeding baby Greys be sure the formula contains all essential nutrients and no refined or processed sugar, chemical dyes or preservatives. A fresh homemade formula is ideal, if made correctly, because it contains nutrients in their most bioavailable form, which is so important for the proper function of a bird's body. If you are feeding a fresh diet with a variety of fruits, vegetables, herbs, grains, legumes, seeds, nuts, and sprouts, you most likely have a Grey in superior health!
Copyright 1999 by Patrick Thrush