The Truth About Vitamin D:
is it the answer to rabbit dental disease?

Frances Harcourt-Brown publishes a new paper on acquired dental disease in house rabbits

Frances Harcourt-Brown is considered by many to be the world's leading rabbit researcher. She is the author of the seminal Textbook of Rabbit Medicine. Although there are many wonderful rabbit medicine practitioners and researchers in this and other countries, Harcourt-Brown, a 1973 graduate of Liverpool University, is generally considered at the forefront of rabbit medicine for a couple of reasons. One reason is that she has espoused rabbit medicine enthusiastically and her practice in the UK is approximately 85% rabbits whereas here in the US, there probably aren't any practices having as high a rate as that of rabbits being seen.

The vets that Bright Eyes Sanctuary bunnies most often go to, SEAVS, or VRA, is about 65% rabbits and that's the highest we've heard of in this country. Arguably also, there is a higher concentration of rabbit owners per capita in the UK than the US. That might be because rabbits are a native species in the UK and are not in the US - there are no American rabbits (well, except for the highly endangered pygmy rabbit); there are only hares (cottontails) in the US. So Harcourt-Brown also has access to a large population of wild rabbits to study.

Harcourt-Brown is particularly interested in rabbit dentistry although she has published many peer-reviewed scientific articles on rabbit medicine. The latest of her works is titled, The Progressive Syndrome of Acquired Dental Disease in Rabbits and was published in the July 2007 Journal of Exotic Pet Medicine. Intriguing article title, isn't it? We thought so, so we bought it and now can relay to you the most important parts of the article for rabbit owners.

For the past year or so, Vitamin D has enjoyed a lot of publicity. If you're like us and stay on top of medical and health news, you've heard a lot of hub-bub about Vitamin D. Certain media outlets, like Life Extension Foundation, are usually years ahead of the rest of the media in reporting on what will soon be hot topics. That's where we read about the Vitamin D 'epidemic' four years ago and have watched with interest as medical media and general media outlets around the country have finally caught up. Not only are people not getting enough Vitamin D, but neither are house rabbits! And, according to Harcourt-Brown and other rabbit researchers, that could be a key cause of rabbit dental disease.

One of our first rabbits, Darth, didn't wake up from his last molar trim. He was an 11 year old little 2 lb. Netherlands dwarf; a darling little fellow. His teeth were particularly bad. His trim frequency had gone from every two months to every two weeks. We ended up driving all over Kingdom Come trying to find the best price on his trims. We ended back at the place where we started though with his final trim because all that driving was wearing us all down.

For his last trim, he was dehydrated from drooling with pain and he didn't wake up. We were very sad but we also couldn't afford that anymore. Still, he lived a long, dignified life. Really, we should have thrown in the towel earlier, but it is very hard to know when it's time to do that.

Not all rabbit dental disease is this bad. But what happens is, your rabbit's molars, which are supposed to have a flat surface, grow pointy and sharp and pierce the tongue, or roof and/or sides of the mouth, or the tongue, causing pain and infection. And they can't eat. The vet puts him under anaesthesia and trims the points down with a Dremel-like tool.

Harcourt-Brown's new article discusses not only appropriate treatment, which has changed in the past several years, but also things like exposure to sunlight, the lack of which may be a key cause of this syndrome.

Let the Sunshine In

Many people don't understand what Vitamin D and sunshine have to do with rabbit's teeth. Good question! Sunlight or sunshine allows your body to synthesize, or build, Vitamin D. Vitamin D allows your rabbit's body to metabolize, or utilize, calcium. Calcium is needed by the teeth and bones. In rabbits, teeth grow perpetually, so they need to be able to effectively metabolize calcium all their life.

Yes, you can get Vitamin D from other sources than sunlight, like fish and algae, and a few other plant sources [editor's note: supplementing Vitamin D in the diet is dangerous and can be toxic if not supervised by a medical professional. Sunlight or artificial lighting simulating sunlight cannot be toxic as the body simply stops synthesizing Vitamin D from these sources when sufficient levels are reached]. But those sources got their Vitamin D by synthesizing it from the UV in sunlight. And not just any sunlight, it has to be a certain wave-length of sunlight which is most accessible around high noon.

We talked to a few vets about Vitamin D lately and its possible relation to this rabbit dental problem. They had varying opinions on whether increased sunlight exposure would be useful, but that's what they were, opinions. It is not really known right now just how this would affect the new syndrome Harcourt-Brown describes in her paper. But she does make some interesting conclusions. "Most pet rabbits are housed indoors or in hutches and are proteccted from sunlight, so they are unable to synthesize Vitamin D," she says. If that is so, then a little sunlight could go a long way toward helping ease not only dental issues, but bladder sludge, bladder stones, and the like.

It should be noted though that the sunlight must fall directly on the animal. Sunlight coming through a glass window has the UV filtered out by the glass and is of no use in the context we are discussing here.

[editor's note: Bright Eyes Sanctuary - BES - has just had some interesting anecdotal experiences which may point to evidence that rabbits may only need the UVB band of radiation from the sun which is NOT filtered through plain glass. This makes sense since rabbits' required photoperiod each day is so short - only 5 minutes and because they are crepuscular and therefore wouldn't usually be above ground when the angle of sunlight is providing both UVA and UVB ].

For people who keep parrots and reptiles, we have long known that this a vital part of those animals' living requirements. Parrot people who live in climates where it is too cold most of the year to take their birds outside, purchase special full spectrum lights which simulate the sunlight spectrum and these have been proven to be beneficial to the birds, and people as well (who suffer from SAD).

There is no possibility of a toxic amount of of this light as the body simply stops synthesizing Vitamin D once it has enough. And, your body (and also your rabbit's) can store Vitamin D for later use. So if a rabbit's required 'photoperiod' is 5 minutes a day, and he gets 35 minutes of noonday sun in one day, that's enough for that week.

There are risks, however, in taking your rabbit outside. Predators, escape, pathogens, pesticides, and other dangers lurk about. If you do take your rabbits outside regularly to munch on some grass in the noonday sun, be sure that the grass is pesticide-free and that it's a dry day. More humid days make for more pathogens swimming about in the air and on the ground.

Harcourt-Brown also says, "Significantly higher PTH and lower blood calcium levels have been found in rabbits without dental disease and living outside in natural conditions." Finally, an interesting note Harcourt-Brown makes, "Despite its prevalence in the pet rabbit population, PSADD is not documented in laboratory rabbits, even though the majority of these animals are not provided with twigs, grass, hay, or any other abrasive diet." [ Ed. But do they get UVB from laboratory lighting?]

She goes on to include, "Similar (dental) radiological changes to those that occur in rabbits with PSADD have been recorded in the incisors of genetically obese laboratory mice. In the mouse study, restricting the food intake prevented the (dental) changes taking place, which is the opposite expected result if the dental pathology was due to insufficient chewing."

These two observations, that lab rabbits do not develop PSADD, and that elimination of obesity in lab mice eliminates PSADD in mice, are packed with potentialities. And more research we're sure will be done on these two topics by Harcourt-Brown. In the meantime, it is certainly a good idea to look into making sure your rabbit gets their true 'photoperiod' each day, or the amount of time required by a certain animal to obtain their needed amount of sunlight.

And also to keep them slim and trim. An aside, cats are the only animals, other than the invertebrates who manufacture their own Vitamin D, that do not require sunlight in order to synthesize the Vitamin D hormone. Ain't that just like a cat?

One final note on this article by Harcourt-Brown, she clearly opines that doing a minimal trim on maloccluded teeth is preferable over the now 'old school' approach, which is to trim them down to the base of the gum line. Doing this, she notes, only causes the tooth to grow back faster and more deformed and destroys enamel of which rabbits have a finite amount during their lifetimes. This would be a good thing to discuss with your vet if your rabbit is going in for regular trims.

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