To give you a better understanding of how UVB lighting and vitamin D3 is linked to calcium absorption I have given a brief description below.

Chameleons will generate their own vitamin D3 when exposed to UVB rays whether it’s from commonly used artificial UV tubes or natural unfiltered sunlight.D3 is an essential part of a chameleon’s metabolism and stimulates the absorption of calcium. Without the correct UVB lighting the chameleon cannot synthesize vitamin D3 and therefore any dietary supplemented calcium cannot be absorbed and is not accessible to the body.

Even with the correct UVB lighting M.B.D. can still become a problem if there is no or very little calcium introduced in their diet(see supplementation), this will result in a serious condition that will lead to the chameleon reabsorbing calcium from their own bones which makes them weaken and often leads to deformities and fractures.

An adult yemen chameleon in the latter stages of M.B.D, the leg has fractured just below the knee.	This X-ray shows how M.B.D will affect bone growth, look carefully and you will see how the bones have warped in the lower leg.

Effects of M.B.D. and what to look out for.

• Lethargy.
• Loss of appetite.
• Leg deformities which take on a u-shaped appearance rather than a definitive 90 degree bend at the elbow.
• Tongue abnormalities like missing their food and the inability to project or retract their tongue correctly.
• A pliable or rubbery lower jaw.
• A slight opening at the front of the mouth that cannot close.
• Spontaneous fractures in the limbs.
• Spinal kinking.
• Poor grip and the inability to lift its body from branches.
• Death.

Baby and juvenile chameleons are more susceptible to M.B.D. as they require more calcium to help them grow; gravid females also need higher levels of calcium to help with egg production.

With the correct lighting, good gut loading of feeder insects and adequate dietary calcium you should never encounter M.B.D. in your chameleons, however if you suspect your chameleon has M.B.D. or shows any of the signs above you should seek immediate veterinary advise and treatment to give your animal the best possible chance of survival.