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Calcium in Cage Bird Nutrition
Author: Robert G. Black

Much of the knowledge of calcium is based on animal studies and on
studies in human nutrition. Little research has been done on birds in
general, and all of that has been aimed at the nutritional requirements
for commercial poultry production. The only research relating to cage
birds is the trial and error feeding that we all employ in trying to keep
our birds in perfect health and breeding condition. Yet, because the
use of calcium in all living bodies is so similar, we can confidently
apply what has been learned in the study of calcium metabolism in
humans and laboratory animals to our cage birds, as well.

Over 90% of the calcium in the body of a bird is in the bird's bones.
The bones are also a storage area for extra calcium and phosphorus,
and the body can withdraw these minerals from the bones whenever
other areas of the body require extra calcium for normal functioning.
The maintenance of normal muscle functions is one area that may
demand extra calcium in order for a hen to have the necessary muscle
functioning to push an egg out through the oviduct.

Calcium is always found in the muscles and organs of the body. Along
with sodium and potassium, calcium controls the heartbeat, the
constant contraction and relaxation of the heart muscle to force blood
through the body. It is also essential for the maintenance of the body's
acid-base equilibrium and for the contraction and relaxation of other
muscle fibers in the body. Calcium also is necessary for the activation
of the enzymes necessary for the metabolism of carbohydrates, fats, and
proteins for energy.

In addition, calcium is vital for the formation and breakdown of a
substance technically called acetylcholine, which is necessary for the
transmission of nerve impulses from one nerve fiber to the next.

Calcium is also required for the absorption of cobalamin, or vitamin B12
in the digestive tract. In cage birds, of course, calcium is a vital
component of the eggshell, and any problem that interferes with
calcium absorption or utilization in the body of the hen will result in
thin-shelled or soft-shelled eggs as a prominent symptom. Clutches
that are smaller than normal can also be a symptom of poor calcium

The need for calcium in cage bird diets is well known, and cuttlebone
and mineral blocks have been a standard part of cage bird feeding for
many years. Cuttlebone is particularly good, as it contains a variety of
trace elements that the cuttlefish has extracted from the seawater that
are vital for the health of all cage birds. Whenever you make boiled
eggs, crush the leftover eggshells and feed them separately to your
cage birds as an excellent and free calcium source.

Once you have supplied these calcium sources to your birds, watch
them closely to be sure that they are actually eating what you provide.
So often, birds will ignore even the most nutritious items and will eat
only the few items with which they are familiar. Is this really so
different from the people who will go into a Chinese restaurant that
offers dozens of exquisite and delicious dishes and then order a
hamburger? Birds will react to new foods in the same manner. The
birds must be eating at least one item that is rich in calcium in order to
get the benefit from it, so be sure that your birds are eating the
offerings that you provide.

If you determine that the birds are not yet eating the foods you have
provided, place the new food scattered on the floor of a clean cage,
removing all other foods at the same time. When the birds get hungry,
soon they will begin searching around for anything that looks like it
might be food. Sooner or later, they will test anything, including these
new foods. After they have eaten a little, return their normal foods
along with some of the new items you are introducing. Within a couple
of days, most of the birds will be eating these new foods regularly,
along with their other usual food items.

Never let them go without food to the point of severe stress and
puffiness. In birds this small, these first symptoms of starvation will
occur within a few hours. Their high body temperatures and very high
rates of metabolism require a continual supply of food all through the
day to supply the energy for the day's activities and to build up an
energy reserve for the coming night. Always return all accustomed
foods by late afternoon so that the birds can eat their fill and build up
their reserves for the night. Healthy finches will not be harmed by this
acclimation process in the least, but it goes without saying that you
should be quite careful in using this method with birds that are already
suffering from severe malnutrition.

Once the birds are eating a calcium-rich food regularly, the next hurdle
in the nutritional process is absorption. Calcium is absorbed primarily
from the acid mixture that leaves the stomach and flows into the
duodenum, the small intestine. Once this mass becomes alkaline,
calcium absorption is reduced drastically. The presence of fats at the
same time will also interfere with the absorption of calcium.

A variety of other factors will also slow or prevent calcium absorption
in the bird's body. As an example, the cereal grains contain a natural
substance called phytic acid which combines with phosphorus to form
phytates. These phytates inhibit calcium absorp-tion, and since cereal
grains form a substantial portion of the commercial feed and seed
mixes, this antagonism can result in a very poor absorption rate for the
calcium consumed by the birds on any diet that is high in cereal grains.
Another acid that goes by the name ofoxalic 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.

Vitamin D

Now we come to the most likely nutritional problem that will affect the
absorption of calcium in the bird's digestive system. That is the
deficiency of vitamin D in the birds' diet. After protein deficiency and
vitamin A deficiency, a lack of sufficient vitamin D in the diet of cage
birds is probably the third most common deficiency noted in their

There are two primary forms of vitamin D in nature. The first has been
classified as vitamin D2, with the technical name of ergocalciferol. This
form of vitamin D is easily used by dogs, humans and most mammals,
but it cannot be used by birds. Vitamin D2 occurs mainly in plant
sources in nature. Thus, any bird diet that is composed solely of plant
products, such as seeds, greens, fruits, vegetables, etc., will not
contain any vitamin D that is useful for the birds. Any bird that is
maintained on a diet that contains only vitamin D2 will soon suffer from
the symptoms caused by vitamin D deficiency, primarily failure to
absorb the available calcium in the diet.

For birds, only the form of this vitamin called cholecalciferol orvitamin
D3 is biologically available. Vitamin D3 is found only in animal
products such as eggs, milk, insects, and liver. Since this is the only
form that birds can use, a seed diet must contain a food from an animal
source rich in vitamin D3 to provide enough of this vitamin for the
birds' health and reproduction. Any birds that are exposed to direct
sunlight for at least an hour a day will be able to synthesize their own
vitamin D on the skin.

There are a variety of symptoms of vitamin D deficiency in cage birds,
most of them related to calcium. In addition to the soft bones of
rickets, in birds thin-shelled and soft-shelled eggs will be a prominent
symptom. Clutches that are smaller than normal will also be a
symptom of too little vitamin D in the diet. Vitamin D3 is crucial to the
absorption of calcium in the digestive tract, and any problem with the
absorption of calcium may be caused by vitamin D deficiency. Also,
eggs laid by the birds that lack sufficient vitamin D will fail to hatch.

At one point in my early breeding efforts, after reading of the beneficial
effect of vitamin D for eggshell formation and calcium use in the avian
body, I began supplementing my birds' diets with additional powdered
vitamin D3 each day. I was totally unprepared for the result. In a
birdroom with about 80 pairs of finches, the next clutches laid
increased in size by as much as 50%. In other words, the birds that
had laid four eggs began laying six, those laying five eggs began laying
seven or eight, and those already laying seven eggs began laying 10
eggs per clutch. The additional vitamin D in the diet had made the
hens' absorption and utilization of calcium so much easier that the
clutch size had increased dramatically.

In any case of poor utilization of calcium in the diet, always suspect a
serious deficiency of vitamin D3 first. Keep in mind that any diet that is
exclusively plant products, with no vitamin supplement that contains
vitamin D3 added, will be totally lacking in this vitamin. The result in
hens will be thin-shelled or soft-shelled eggs. In babies, the bones will
not harden, but will remain soft and pliable, unable to support the
weight of the bird.

The commercial poultry starters, game bird starters, cage bird
crumbles and pellets, all will contain adequate amounts of vitamin D3
for the birds' health. Even monkey pellets contain vitamin D3, since
the monkeys from the Americas also must have this form of vitamin D
in their diets. If you plan to try any type of dog or cat food for your
birds, be sure to check the label carefully, however. Dogs and cats can
use vitamin D2 in their metabolism quite effectively, and many dog and
cat foods do not contain vitamin D3. Never forget that for birds the
only metabolically active form of vitamin D is vitamin D3.


Thus far, a number of nutrients have been mentioned that will affect the
absorption and utilization of calcium in the avian body, but the most
significant has not yet been mentioned. That is phosphorus.
Everywhere in the body, calcium and phosphorus work together. In
the bones, approximately two parts of calcium join with one part
phosphorus and other minerals, along with several vitamins, to form
the honeycomb structure of the bones. This ratio also needs to be
maintained in the other areas of the body for the best and most
effective functioning of all of the body's organs. A problem will arise if
the proportions of phosphorus in the body are greater than the calcium,
as this is sure to interfere with the normal use of calcium.

It is for this reason that I always recommend keeping a calcium source
in front of the birds. An available calcium source is always necessary
for cage birds because most plant foods are very high in phosphorus,
while the bird's body needs a much higher proportion of calcium. This
additional calcium available constantly is crucially important to enable
the birds to balance the calcium/phosphorus ratio in their diets and in
their bodies. They will eat this calcium supplement instinctively
whenever they feel the need to balance their intake of calcium and
phosphorus. If you supply crushed eggshells or any other calcium
source free choice to the birds, you can be certain that they will not eat
too much of it. But their instinctive craving will cause them to eat
what is needed each day to balance their intake of calcium with the high
percentage of phosphorus in plant food items.

In summary of the information presented here, calcium is vital for the
health and well-being of your cage birds. However, though an actual
deficiency is impossible, calcium absorption and use can be severely
limited and even eliminated by the presence or absence of a variety of
other minerals and compounds. Be sure your birds are getting enough
vitamin D3 for the absorption of calcium, keep a calcium source available
for them at all times so they may balance their own needs for it as the
other nutrients are consumed, and you should have no further problems
relating to calcium in the care and maintenance of your cage birds.

Copyright 1998
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Messages in this topic (1)
4. Exchangeable Calcium
Posted by: "Kathy Heaton '" [email protected] [email protected]
Wed Apr 7, 2010 10:52 am (PDT)

Exchangeable Calcium
by Tom Riggs and Ross Bishop

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 supplement 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 will be even more
Copyright © 1999 National Finch and Softbill Society 
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