Metabolic
Bone Disease, Calcium and Vitamin D3
Metaboilic
Bone Disease (hypocalcemia ) is defined as "an absolute decrease
in total bone mass". In general terms it is the "borrowing"
of calcium from the bones to ensure the correct amount is found in
the cells and blood. i.e. the bones of the animal are used as a calcium
store.
Only 1% of calcium is found outside the bones but this 1% is essential
for muscle contraction (such as the heartbeat), nerve function, blood
clotting, metabolic functions and enzyme activity.
This removal of calcium from the bones without replacement causes
weak and brittle bones and fractures are commonplace. Eventually if
the calcium deficit is not reversed the disease is fatal.
MBD is
generally caused by insufficient calcium levels (or wrong form of
calcium) in the diet, wrong calcium to phosphorus ratio, too much
protein in the diet, wrong temperature for digestion, or insufficient
UVB to allow synthesis of Vitamin D3 / insufficient vitamin D3 to
allow calcium absorption.
Organ dysfunction
(Liver and Kidney) is another cause although somewhat rarer than the
above.
Another
form of hypocalcemia sometimes occurs in gravid female chameleons.
When their eggs pass through the shell gland the calcium requirement
is too much or too quick to leach from the bones. This is a very serious
condition and one which prevention by feeding a gravid female an especially
good diet is better than cure. Note the suggestion to feed well rather
than supplement. Too much calcium by supplementation can cause egg
binding whereas dietary calcium take up tends to be better regulated
by the chameleon.
Visual signs
Early signs can be tongue dysfunction and week grip. Pliable, swollen
or more rounded jaw bone - the strong muscles of the lower jaw pull
the bone round and gives a shorter appearance. Often the jaw is overshot
as a result of this.
Limbs are
also pliable and/or swollen and may show fractures (often multiple)
and/or deformities. Classic signs are the limbs appearing to have
an extra joint or irregular swellings. The first is caused by fractures,
the second by the body trying to sure up the weakened bone structure
with fibrocollagenous connective tissue.
The animal
may appear lethargic. Anorexia is common as the jaw becomes too weak
to function properly. The animal no longer tries to climb and rests
at the bottom of the enclosure. Inability of the limbs to raise the
body off the ground is a sign of advanced MBD. The limbs function
but without power sufficient to lift or move the body.
Once the
calcium levels in the blood drop too low muscle tremors and laboured
breathing can be observed. Worryingly it is usually the muscle tremor
stage where many keepers notice something is wrong. At this stage
"home remedies" should not be tried. A trip to the vets
is needed.
If untreated the muscle tremors will eventually lead to cardiac failure
and death.
Here is
a female Veiled Chameleon with advanced MBD. Note the front legs
are curved. This is caused by multiple breaks. The animal could not
support
its own body weight.
Sadly the
animal had to be euthanased.
Clinical
Tests
X
rays can be used to determine bone density and degree of severity
of the disease. They can also show if a female is gravid and hence
going through the strains of egg production.
Blood serum
tests may be miss-leading (often shows all clear) as the reason the
calcium is leached from the bone in the first place is to maintain
calcium levels within the normal range in the blood (amongst other
places).
Calcium
/ Phosphorous ratio
Phosphorus combines with calcium to form calcium phosphate, which
forms the majority of bone in the body.
Ideally a diet should have a calcium:phosphorus ratio of 1:1 to 2:1.
Most insects commonly fed to Chameleons are high in phosphorus and
low in calcium hence the standard advice that insect prey should regularly
be dusted with calcium powder.
Below is a table showing the nutritional contents of commonly available
feeder insects kindly supplied by Peregrine Livefoods.
|
|
|
|
|
|
|
|
|
Species
|
%
moisture
|
%
fat
|
%
calcium
|
%
phosphorus
|
Ca:P
ratio
|
%
protein
|
|
| Mealworm |
68
|
8.5
|
0.016
|
0.3
|
1:19
|
18.9
|
|
| Morio |
59.8 |
15.2
|
0.022
|
0.21
|
1:10
|
19.5
|
|
| Waxworm |
65.1
|
15.5
|
0.037
|
0.19
|
1:5
|
15.5
|
|
| Locust |
73.2
|
5.8
|
0.035
|
0.18
|
1:5
|
15.9
|
|
| Banded Cricket |
71.8
|
6.3
|
0.14
|
0.22
|
1:1.5
|
16.5
|
|
| Black Cricket |
66.7
|
12.0
|
0.18
|
0.22
|
1:1.2
|
15.8
|
|
| Silent Cricket |
68.8
|
9.3
|
0.17
|
0.22
|
1:1.3
|
16.4
|
|
| Brown Cricket |
70.7
|
4.4
|
0.089
|
0.28
|
1:3
|
19.8
|
|
Crickets
were fed on layers mash and potato. Locusts on cabbage.
Calcium
Chameleons use calcium according to their metabolic rate.
Lowland species such as Veileds and Panthers require more calcium
than montane species such
as Jacksons and Fischers.
This is because their metabolism is faster as they are kept at higher
temperatures.
Babies need more calcium than adults and gravid females need more
than males.
Supplements and percentage of calcium
Calcium Carbonate 40%
Limestone 38%
Calcium Lactade 18%
Calcium Gluconate 9%
Bone Meal 24% calcium, 12% phosphorus
Interestingly
the chameleons body absorbs calcium more easily from low volume calcium
supplements.
Hence vets will usually treat MBD with Calcium Gluconate however this
is when calcium levels are clinically proven to be low.
For routine
supplementation Calcium Carbonate is preferred because it is safe
and effective.
Limestone powder is a very good second choice.
Calcium
Lactade (sometimes called calcium sugar) is water soluble so can be
added to the crickets drinking water to increase their calcium content.
Try to
avoid "homemade" supplements such as bonemeal and cuttlefish.
These can contain high levels of toxic metals such as lead and mercury.
Commercially produced Calcium supplements are usually screened for
such toxins.
Hard water
(or bottled water with added calcium) helps get additional calcium
into chameleons.
Some studies suggest hard water give chameleons more calcium than
regular dusting the food with calcium powder.
Good nutrition alone is not enough to prevent or correct MBD
Vitamin D3
Vitamin D3 (a hormone) is needed for calcium absorption in the intestine.
The major problem with Vitamin D3 deficiency is, therefore, reduced
calcium absorption by the intestines regardless of calcium availability
in the diet.
Vitamin D3 starts production in the reptiles body by UVB light reacting
with cholesterol in the reptiles skin. This in turn synthesises the
production of pre Vitamin D3.
Pre- Vitamin D3 is transferred by the kidneys then the liver into
Vitamin D3.
In tests
on Panther Chameleons it was shown that dietary D3 is not as easily
used by the body as synthesised D3. Therefore supplementation should
only ever be used as the name suggests, to supplement good husbandry.
i.e. calcium rich diet and sufficient UVB light
Inhibitors
of calcium absorption
Temperature
Unless the animal can attain its preferred temperature it will not
be able to digest properly which will prevent calcium being absorbed
from the diet.
Stress
Stress hormones reduce or shut off the digestive system where calcium
is absorbed plus affect the synthesis of Vitamin D3 (another hormone).
Lack of
UVB
Old or incorrect UVB lighting.
High protein
Diet
Main source of phosphorous is protein so a high protein diet unbalances
the Calcium to phosphorous ratio and therefore contributes to MBD
Oxalates
Oxalates found in certain greens such as cabbage, and spinach (commonly
used as "gutload") bind with calcium making it unusable
so should be avoided. Stick to Spring Greens, water cress or dandelion
leaves.
High fat
diet
Dietary fat also lowers calcium absorption so feeding waxworms which
are high in fat (even when dusted with calcium powder) are not sufficient
to replace a calcium deficit.
Dehydration
Healthy kidneys are vital for D3 synthesis. Correct humidity reduces
the workload on the kidneys.
If
you suspect MBD
Firstly the cause needs to be identified and rectified. More likely
to be husbandry.
Climbing
perches etc should be removed and wide low perched should be used
instead. A more restrictive sized enclosure would again help prevent
further damage.
The enclosure should be kept at the upper level of the animals preferred
temperature. Humidity should be measured and within preferred levels.
Any outside stress factors should be removed. Consideration should
be given to moving the enclosure into a quieter room if possible.
Renew the UV bulb and decrease the gap between the reptile and tube.
Veterinary
advise should be sought. MBD should not be treated by home remedies.
Particularly as some of the symptoms of hypercalcemia (too much calcium)
are similar to too little.
High
levels of flouride in drinking water
High levels
of fluoride found in some tap waters can cause symptoms that mimic
the signs of MBD.
If your
chameleons are experiencing signs of MBD even though husbandry and
nutrition is correct you should check the levels of flouride in the
water. Each Water Authority publishes an analysis of their drinking
water.
Recommended maximum levels for humans are 1.0 ppm (parts per million)
fluoride. Or 1mg per litre. Fluoride has a narrow safety range with
4 ppm posing serious health risks to humans. Although no serious testing
of flourosis in chameleons has been done it is suggested that the
human limit is probably on the high side.
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