A common health problem for pet reptiles and tortoises is a lack of calcium. "Low calcium levels result in a whole set of bone, joint and general health problems and, when severe, can cause a common condition called metabolic bone disorder," explains veterinarian Dr David Gething of Creature Comforts www.creaturecomforts.com.hk.

MBD occurs when the bones are leached of their normal calcium levels, becoming brittle and fibrous. The low calcium levels also affect other body functions, such as normal muscle action and walking, immunity and general health. "MBD can be debilitating and painful, especially if severe. It can affect the legs and joints, making walking difficult."

Reptiles with MBD will commonly also have a weak mouth and jaw, and can break their jaw while they are eating. Lizards with MBD will commonly walk with a limp, or not walk at all, and tortoises often develop a weak, flexible shell.

Gething says: "As it becomes more severe, it often causes the reptile to hide away, not eat, lose weight and, if not treated, it is life-threatening."

MBD takes time to develop, and symptoms can be fairly mild and subtle at first, the vet says.

However, it is not often until the pet has a broken leg or severe bone deformities that the owner takes action. "The most frustrating thing is that MBD is easily preventable with correct care and housing."

A low overall level of calcium is often due to poor diets, such as plain lettuce or fruit for herbivorous reptiles, or only meat for the carnivores. Gething says: "These diets are extremely low in calcium, as well as other vitamins and minerals, and over a fairly short period of time a deficiency will develop. Like all of us, reptiles need a varied, balanced and healthy diet."

A second factor is low vitamin D3, which is vital for normal calcium metabolism.

Gething says vitamin D3 is produced by the skin when exposed to sunlight, or ultraviolet light, and reptiles kept indoors are especially prone to low D3 levels. "The good news is that prevention and treatment are relatively straightforward."

First, food should be sprinkled or dusted daily with a small amount of reptile mineral powder. The vet says there are a number of brands, and the mixtures are generally a combination of calcium, phosphorus and other essential minerals and vitamins.

Pet reptiles and tortoises should also be given a balanced and varied diet suitable for their age and breed. "Requirements vary widely between species, so make sure to check what your pet needs. Supplementing a natural diet with a good brand of reptile pellets or commercial tortoise food can also be an excellent way to prevent deficiencies.

"It's also important that all reptiles and tortoises are exposed to at least 12 hours of UV light per day. Natural sunlight is an excellent source of UV light, but fluorescent lights designed for reptiles are also suitable," the vet says.

In either case, make sure that there is adequate ventilation to prevent overheating and do not place a screen (such as glass) between the reptile and the light source. If UV lamps are used, a timer should be set to ensure a normal day's length of light.

It's also vital to make sure that your pet's enclosure is at the correct temperature, and has adequate room for exercise, Gething says. Reptiles are cold-blooded, and much more reliant on the environment for maintaining their correct body temperature, which in turn has a significant effect on their bodily functions.

Low temperatures will slow the metabolism and affect body chemistry. Exercise is also very important in maintaining muscle and bone strength and function, the vet says. Many lizards also have specific housing needs such as climbing branches or basking rocks.

Tortoises, too, have highly variable requirements depending on their species - some will always stay in water, some need to be able to get out and rest, and some are completely land-based and never even drink water, getting all the fluid they need from their food.

"Make sure you find the correct requirements for your pet."

If you suspect low calcium levels or metabolic bone disorder, Gething recommends contacting a vet familiar with reptiles and exotic pets. "Treatment is generally successful, especially if the condition is diagnosed early. Mild cases will respond well to simply supplementing calcium and ensuring good lighting, but in more advanced cases, oral medication or even calcium injections may be required."

Metabolic bone disorder is a common problem in pet reptiles and tortoises, but, as Gething says, it is an easily preventable disease if the diet, lighting, temperature and housing needs of the species are met. 

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