What is MBD?
Can you heal an animal with MBD? What does MBD do to reptiles? And why do reptile keepers suddenly become part-time nutritionists, lighting engineers and calcium dust enthusiasts? Let’s dig in.
Metabolic bone disease (MBD) is a collection of deficiencies and/or abnormalities involving minerals in an animal’s body, including calcium, magnesium, phosphorus and vitamin D3. When these essential minerals are lacking, the animal’s skeletal structure weakens as the body releases calcium from the bones to prevent hypocalcemia.
(Hypocalcemia is the lowering of blood calcium levels, which can cause lethargy and gastrointestinal issues — basically your reptile’s body waving a tiny white flag and saying, “Excuse me, we appear to be falling apart.”)
The body wants to avoid hypocalcemia at any cost and will draw on its own calcium reserves to prevent it, even to the point of leaching calcium from its own bones. In other words, the reptile version of “borrowing from Peter to pay Paul” is literally stealing from its skeleton.
MBD is a debilitating disease and will initially present with lethargy and disinterest in food. Further progression leads to weakened bones and visible deformities. In bearded dragons this can appear as an underbite and shortened neck, leopard geckos may develop “rubber jaw” where the animal loses skeletal rigidity, and in severe cases, deformed front legs. Crested geckos may develop crooked tails and spinal curvature, while other lizard species experience similarly debilitating symptoms.
Internally, the bones are undergoing a long and painful process as calcium is continuously removed. As explained above, the calcium that gives the bones their strength begins to leach out, which in turn affects the bones’ ability to reabsorb it correctly, creating a painful and progressive cycle. No one truly knows the full extent of the internal organ damage sustained during this process, but suffice to say, it would not be an enjoyable experience. Think less “majestic desert dragon” and more “brittle breadstick.”
Metabolic bone disease cannot be reversed. Once the damage has been done, it is permanent and often disfiguring. From pyramiding in tortoise shells to twisted limbs in lizards, the best cure for MBD is prevention. Ensuring your reptile receives the correct supplementation of vital minerals, at the correct dosage, is the key to maintaining a healthy animal and avoiding your gecko accidentally evolving into modern art.
But what supplements do you need to use?
We use and recommend a 7-day routine of calcium, vitamin/mineral and calcium-plus-multivitamin supplementation. This routine changes depending on the species being fed. The table below shows the supplementation schedule for a Testudo species tortoise:
Yes, your tortoise now has a supplement routine more organised than most humans.
Ca:P = 2:1
Reptile Systems Calcium Ultra contains 99% calcium to 1% magnesium and is used for 3 days of the week (Mon, Wed & Fri).
Reptile Systems Vit-A-Min contains vitamins A, E, B3, B5, B7 and B9 with trace minerals Iron, Iodine, Copper, Manganese, Zinc and Phosphorus with a calcium base and is used for 3 days a week (Tues, Thurs & Sat).
White Pythons Nutrirep contains Calcium, vitamins D3, A, C, E, B1, B2, B6, B12, nicotinic and pantothenic acids, and minerals including Iron, Cobalt, Manganese, Copper, Zinc, Iodine and Selenium, and is used on the final day of the week (Sun).
This schedule allows for maximum intake of trace vitamins, minerals and calcium necessary for a healthy tortoise. Or, to put it another way, your tortoise ends up on a stricter wellness routine than most gym influencers.
This may seem excessive, but in a natural setting tortoises would consume a far more varied diet than we can realistically provide in captivity. Wild tortoises may feed on more than 200 different plant species throughout the year. Those plants grow in different soils, absorb different nutrients and contain varying nutritional values themselves. Captive tortoises, meanwhile, are often presented with the reptile equivalent of “salad again” with only a dozen or so plant species readily taken by our tortoises.
Larger reptiles in the wild would also prey on numerous species of insects, arachnids, smaller reptiles, mammals, birds and eggs, often consuming them whole — skeleton, shell and internal organs included — which provides a direct natural calcium source. Nature’s version of “nose-to-tail dining” is considerably more hardcore than ours.
Exposure to natural UV light from the sun also allows reptiles to synthesise vitamin D3 far more efficiently than under artificial lighting. While modern UV systems are excellent, nothing beats the giant fusion reactor in the sky that has been doing this job reliably for roughly 4.6 billion years.
A combination of correct supplementation and proper feeding frequency helps prevent MBD — but supplementation alone is not enough. As we discussed in a previous article regarding the relationship between Calcium, D3 and UV, lighting is essential in ensuring supplements are absorbed and utilised correctly within the body.
Even with perfect vitamin and mineral supplementation, without the correct UV exposure — at the proper level, within the correct Ferguson zone for the species and maintained regularly — MBD can still develop. UV output declines over time, typically within 6–18 months depending on the bulb brand and type, so replacement schedules are extremely important.
And yes, reptiles absolutely care about bulb quality, even if they continue staring blankly at you while standing directly under the expensive one you just bought.
It is also vital that UV lighting is installed correctly. Just because a reptile comes from a rainforest environment does not automatically mean it requires a low-level 5–7% UVB source. In larger enclosures, or where UV light passes through mesh tops (which can reduce UV exposure by approximately 30%), a stronger 10–12% UVB may actually be more appropriate to provide the correct exposure for the animal.
In short: good supplements, proper UV, correct temperatures and a varied diet are all essential pieces of the puzzle. Miss one, and your reptile’s skeleton may begin filing formal complaints.
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