Metabolic bone disease is a common condition seen in almost all house rabbits with dental disease.
The disease is similar to osteoporosis in humans, where there is lack of calcium in the bones. The actual disease is complex and many factors are involved.
The three most important elements involved in metabolic bone disease are calcium, vitamin D and parathyroid hormone. These three factors work closely to maintain calcium homeostasis in the blood.
Bone acts as a storage point for calcium and phosphorous, when blood calcium is low, the body retrieves calcium from bone to maintain calcium stasis.
Dietary calcium needs to be more than 0.44% for blood calcium to remain normal in rabbits. Rabbits eating a diet with lower than 0.44% calcium (most rabbit mixes) will have low levels of calcium in the blood.
Kept in the dark
Exposure to sunlight is crucial for vitamin D synthesis. Vitamin D is essential for absorption of calcium in the gut. Animals with low blood calcium often compensate by producing vitamin D (with exposure to sunlight), and thus absorbing calcium in the gut. This is assisted by parathyroid hormone.
House bunnies, restricted from sunlight and eating a diet low in calcium, cannot maintain calcium levels, and therefore obtain calcium from the bone. Bone then weakens, resulting in dental disease.
Metabolic bone disease is probably the main reason why house bunnies develop dental disease so often. Wild rabbits have adequate exposure to sunlight and free access to grazing. Acquired dental disease is not seen in wild rabbits at all.