Preventing Metabolic Bone Disease (MBD) in Lizards
One of the most common diseases in captive lizards is metabolic bone disease, or MBD. MBD actually refers to a group of disorders, but it ultimately results in weakened bones--think osteoporosis, but for reptiles. Calcium deficiency is the most common culprit of this disease; fortunately, it is completely avoidable. Whereas carnivorous reptiles like snakes obtain the proper nutrients and balance from their prey, lizards--whether insectivores, herbivores, or omnivores--are a bit more complicated. For calcium intake, there are three important factors in play: calcium (of course), phosphorus, and vitamin D3.
Lizards in the wild consume a wide variety of food to satisfy their nutritional requirements; in addition, food items in the wild tend to have more varied gut contents than raised feeder insects. Lizards in captivity, however, are given limited types of food items. Insectivores might only have one or two staple insects offered, and herbivores might only be given one or two types of vegetables. This limit could result in the lack of some nutrients, including calcium. However, there are several ways to ensure that your reptile is receiving enough calcium, even with a limited diet.Dusting food items is the easiest way to provide additional dietary calcium. Dusting is the process of sprinkling a small amount of powdered calcium supplement on the food items right before offering that food to your lizards. There are numerous commercially available calcium supplements which are tailor made for reptiles. At Josh’s Frogs, we use RepCal’s Calcium and RepCal’s Calcium with D3 when dusting our insects and vegetables for additional calcium. Other calcium supplements, like Repashy’s Calcium Plus, work just as well.Another way to increase calcium is by gut loading insects. Gut loading simply means providing your feeder insects with nutritious food a few hours before feeding them out; those nutrients are then made available to your lizards when they eat. There are two primary options: high calcium greens, like collard greens or kale, or commercially available gutloads and watering gels. For herbivores or omnivores, you can simply provide vegetables high in calcium--make sure to do some research before offering new greens though; spinach, for example, should be avoided since it contains oxalate, which binds to calcium and makes it unusable.Finally, you can supplement your lizard’s diet with high calcium feeder insects. Feeders like black soldier fly larvae/phoenix worms (for smaller lizards) and hornworms (for larger lizards) are high in calcium and make great occasional additions to your lizard’s diet.
It is generally agreed that reptiles need a 2 to 1 ratio of calcium to phosphorus in order to properly utilize calcium--that is, they need to consume twice as much calcium as phosphorus. This ratio accentuates the importance of providing some additional calcium to your reptile’s diet instead of relying solely on the small amount provided by some food items. Crickets are a prime example: they contain more phosphorus than calcium, and fed to a reptile with no other insects, gut loading, or dusting with supplements, a diet of crickets alone would almost definitely lead to MBD.
Vitamin D3 is an extremely important vitamin when it comes to preventing MBD: without it, reptiles cannot absorb calcium at all. In the wild, reptiles synthesize their own vitamin D3 when exposed to ultraviolet (UV) light. In captivity, there are two ways to provide vitamin D3.The first way is to provide UV light for your reptile. This will allow your reptiles to naturally synthesize their own vitamin D3. For diurnal (active by day) reptiles like chameleons, day geckos, and bearded dragons, there is no better option for vitamin D3. Nocturnal animals can also be provided UV light by day, but they can also be supplemented vitamin D3.The second way to provide vitamin D3, then, is to provide it in the form of the supplement, like RepCal’s Calcium with D3. Whereas nocturnal animals can utilize vitamin D3 in supplement form, some diurnal reptiles, like chameleons, cannot. For this reason, while supplemented D3 works for nocturnal lizards, it should never be used as a replacement for direct UV exposure for diurnal ones.
While you’re browsing for a calcium supplement, it’s recommended that you look into getting a reptile multivitamin supplement as well. It’s also recommended that, when gut loading insects or offering greens to your herbivorous or omnivorous reptiles, you choose a variety of vegetables, not only those high in calcium. Because of the interplay of vitamins and minerals, preventing MBD--and other nutritional deficiencies, for that matter--requires that your animal is receiving a nutritious diet overall. Gut loading, supplementing, and providing a wide array of food items, be it vegetables or bugs--these are the keys to a healthy diet for your reptile. The fewer food items that are offered, the more care should be given towards making up for calcium and other nutritional deficiencies through gut loading and dusting.
This article only serves as an introductory guide to avoiding MBD by outlining basic ways to increase calcium sources for captive reptiles. Want to read more on captive reptile nutrition? Allen Repashy, an expert in captive reptile nutrition, has a great article written here. LLLReptile also has a great article on captive reptile nutrition here.