Keeping Reptiles Newsletter
  Issue 14 Vol 6 December 2010
Nutritional Metabolic Bone Disease In Reptiles - Part 1 In this Issue

By Roberta A. Avila-Guevara CVT

Nutritional Metabolic Bone Disease or NMBD, is not just a bone disease. It is made up of several metabolic disruptions that affect the skeletal system of captive reptiles. Its development is due to husbandry and dietary mismanagement, therefore education is the foundation to its prevention. Knowledge of bone development and skeletal health, as well as the pathology of the disease allows the reptile keeper to establish proper husbandry practices.

The Process of Bone Health
Bone health is composed of several elements that work together to maintain the integrity of the skeletal system. These elements are comprised of internal and external components.

This mineral is responsible for many biological functions. Because it is one of the most abundant minerals in the body, calcium is responsible for muscle contractions, blood clotting, nerve transmission, heart muscle function, and the development and integrity of bones and teeth. 98.8% of calcium is stored in bone. The other 1% is intracellular, and 0.1% remains in the extra cellular space, it's found in three forms.

  1. 9% is non-ionized and not usable. It combines with anionic molecules such as phosphorus.
  2. 41% is protein bound. It can not diffuse across cellular walls and is not usable.
  3. 50% is ionized. This is the calcium that is usable and is the most important form in blood.

The majority of this mineral is used to build and maintain teeth and bone. In order for this to occur, it must remain in a calcium to phosphorus ratio of 2:1. The most important function of phosphorus as related to NMBD relates to the skeletal system, however it's important to understand other functions in order to recognize clinical signs of NMBD. These functions include metabolism of proteins, fats, and carbohydrates, muscle formation, and production of energy.

Ultimobrachial Gland
This gland is located near the thyroid, thymus, and parathyroid glands in the area of the heart. In reptiles it is believed to produce calcitonin in order to maintain a healthy skeletal system by preventing high levels of calcium in blood. It does this by targeting the kidneys to excrete excess minerals, targeting the intestines to absorb less calcium, and the bones to store more calcium.

Parathyroid Glands
The parathyroid glands are small glands located near the thyroid gland. They produce PTH, or parathyroid hormone in response to low calcium levels. PTH targets the same organs as the thyroid gland; however this hormone produces the opposite effect: kidneys retain minerals; the intestines absorb calcium, and the skeletal system releases calcium from its stores. The goal is to maintain appropriate calcium levels in blood.

Vitamin D and UVB Rays
Vitamin D acts as a hormone. It is supplied through dietary supplements or through the reptile's skin in a conversion process that includes UV rays. This vitamin is responsible for the absorption of calcium and comes in two forms. D2 is found in plants, and D3 is produced in the animal's skin. Either form can be utilized by most reptiles.

The sun releases three forms of ultraviolet radiation, UVA, UVB, and UVC. UVB radiation is critical for most herbivores reptiles such as the Green Iguana, because it's responsible for the conversion of cholesterol into an active form of vitamin D in the skin. Without UVB radiation, this will not occur.

Vitamin D3 and Calcium Metabolism
The process begins with exposure to UVB radiation. Cholesterol is converted into a vitamin D3 precursor called provitamin7- Dehydrocholesteralin. This is inactive and initially makes its way to the liver where it's converted into 25- Hydroxovitamin D. From there it's sent to the kidneys, converted into 1, 25- Dihydroxyvitamin D, or the active form of vitamin D3; and released into the intestinal tract where it is absorbed via passive diffusion across the intestines.

Part 2 of this series on NMBD will cover the disease process and what causes it..

Roberta A. Avila-Guevara CVT is a practising Certified Veterinary Technician and has been published in several veterinary technician journals. 

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Captive Bred or Wild Caught?

By Aliza Arzt

People who purchase reptiles often have the choice between a wild caught or captive bred animal. Some people choose the wild caught animal because they are attracted by the often lower prices and don't consider the ramifications of their choice. There are a number of disadvantages to working with wild caught animals, but, under the right circumstances, there may be good reasons to choose them.

Captive bred reptiles are acclimated to living in a limited enclosure from birth. If kept properly, they live their entire lives in relatively sterile, parasite-free environments. They may exhibit traits, such as albinism, that would not be conducive to survival in the wild. They are carefully maintained and treated medically if they exhibit any obvious problems.

In contrast, wild caught reptiles are not accustomed to living in cages, and may be used to roaming over large areas in their native habitats. They are often caught and sold by local people who are paid by the "piece" and may not be knowledgeable about their husbandry needs. Wild caught animals are usually exported internationally and may change hands several times before reaching the market. In the time between capture and reaching the market, these animals are often kept in inappropriate and overcrowded conditions. They may have internal and external parasites which spread due to stress and overcrowding. It's not unusual for wild caught reptiles to require medical treatment for dehydration, parasites and injuries such as bites or limb amputation.

With all the disadvantages of wild caught reptiles described above, why would anyone choose them? Unfortunately, people do buy wild caught animals because the price is often lower. In these cases, it's not unusual for the animal to die after a short time, or, worse, to infect the buyer's other animals. Still, there are some good reasons to choose wild caught reptiles:

Some reptile species have not been successfully bred in captivity and can be obtained only from the wild.

Wild caught reptiles are an excellent source for out-crossing when breeding, especially for captive bred species with a limited gene pool, or "over-bred" species such as Leopard Geckos.

Occasionally, genetic mutations crop up in wild caught populations and can enrich the morph diversity of the species in captivity. This is currently an important factor in the recent explosion of new African Fat Tail Gecko morphs.

Endangered reptile species can be propagated in captivity and "saved" as a species through careful captive breeding of wild caught specimens.

Anyone choosing a wild caught reptile, needs to take appropriate actions to insure a successful experience:

Buy from a reputable importer.

Choose an animal that looks as healthy as possible.

Observe strict quarantine between the new reptile and the current collection: keep the new reptile in a separate room, care for it after caring for the current collection, observe strict hygiene.

Be prepared to re-hydrate treat a wild caught reptile and to treat it for internal parasites or mites. A veterinary examination with a fecal sample is a must to insure and achieve good health.



Aliza Arzt is an editor for Gecko Time ( and has been and avid keeper of reptiles foir many years.

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Bearded Dragon with Metabolic Bone Disease


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