Vitamin D and UVB question

Moozillion

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My Mississippi mud turtle eats Hikari Sinking Carnivore Pellets happily. The ingredient list says it's fortified with Vitamin D (and lots of other things).
If the purpose of the UVB light is to help them make vitamin D, but she's getting it in her diet, do I NEED a UVB bulb?
I currently have a mercury vapor bulb for her basking spot (and she LOVES to bask!) but would it be okay to just use a heat lamp once the MVB goes?
 

Tom

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Vitamin D2 is ingested. In the presence of the right wavelength of UVB in warm skin, D2 is converted into D3. Will finally convinced me that tortoises can ingest D3 and survive without UV just fine. Not sure if dietary D3 is sufficient for all chelonians, or all reptiles, but most reptiles, especially carnivores, get D3 from their food. Blue tongue skinks can use dietary D3 and never see any UV for their whole life. All snake species that I know of do this too.

I don't know if Mississippi mud turtles can use dietary D3 or not, but my best guess would be that yes they can. Now the question is, what type of vitamin D is in your food? I think both MarkW and Will @Kapidolo Farms are more knowledgable than me on this subject. I'd like to hear what both of them have to say.
 

Markw84

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There are two types of vitamin D. D2 and D3. D2 is the type of vitamin D found in plants. D3 is the vitamin D found in animals. Both are manufactured with sun exposure by the plant or animal. Both types are used as food supplements or in vitamin pills. D2 is also readily avialable in its synthetic version made from the cell membrane of a fungus that is exposed to UV light. This is a much easier and less expensive way to get vitamin D and is often what is found in lesser expensive supplements. So both can be taken in the diet and used by the body that way. Only D3 is manufactured by our, or our tortoises, body in the skin with UVB exposure.

To @Moozillion 's question, aquatic turtles do get quite a bit of their D3 from dietary sources. Some fish is a good source of D3. The supplements added to most good turtle foods is also a good source of D3. I have raised many aquatics with no UVB for extended periods with no ill effects in several studies. I like to use good UVB for my aquatics, but they certainly can get dietary D3 and can use that effectively.

However if using a D2 supplement, or relying on feeding plants that have Vitamin D - which would be D2 - there is a caution. In humans studies have conclusively shown D2 is not utilized well by the body. Some studies showed it had no effect on improving bone health. It also does not last long in the body as D3 does. Does this translate to tortoises? I don't know for sure, but I think it is worth insuring there is either good UVB exposure, or good quality D3 supplement in the diet. If relying on dietary D2 naturally in some plants that are fed (mushrooms can be high in D2) it would be important to not rely on that alone long term, in my opinion to be safe.

Will is the dietary Guru, so let see what @Kapidolo Farms has to add.
 

Kapidolo Farms

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the D's pathways are complicated with recycling and feedback loops and genuinely unsettled among people who put much more effort into understanding it than I have.

I feel certain that mud turtles can get D3 directly from diet, my own first hand experience with this regards three stripped mud turtles living well indoors on what was called trout chow (contained D3). I do not know the ingredients anymore of those chows, but often suggest to people to use 'gold fish pellets'.

I recently heard @Markw84 narrate that cold water Koi food, if I got that right, works. If it has D3 in its formulation, it's probably going to work.
 

Moozillion

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Vitamin D2 is ingested. In the presence of the right wavelength of UVB in warm skin, D2 is converted into D3. Will finally convinced me that tortoises can ingest D3 and survive without UV just fine. Not sure if dietary D3 is sufficient for all chelonians, or all reptiles, but most reptiles, especially carnivores, get D3 from their food. Blue tongue skinks can use dietary D3 and never see any UV for their whole life. All snake species that I know of do this too.

I don't know if Mississippi mud turtles can use dietary D3 or not, but my best guess would be that yes they can. Now the question is, what type of vitamin D is in your food? I think both MarkW and Will @Kapidolo Farms are more knowledgable than me on this subject. I'd like to hear what both of them have to say.
Thanks, Tom!:):<3:
 

Moozillion

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There are two types of vitamin D. D2 and D3. D2 is the type of vitamin D found in plants. D3 is the vitamin D found in animals. Both are manufactured with sun exposure by the plant or animal. Both types are used as food supplements or in vitamin pills. D2 is also readily avialable in its synthetic version made from the cell membrane of a fungus that is exposed to UV light. This is a much easier and less expensive way to get vitamin D and is often what is found in lesser expensive supplements. So both can be taken in the diet and used by the body that way. Only D3 is manufactured by our, or our tortoises, body in the skin with UVB exposure.

To @Moozillion 's question, aquatic turtles do get quite a bit of their D3 from dietary sources. Some fish is a good source of D3. The supplements added to most good turtle foods is also a good source of D3. I have raised many aquatics with no UVB for extended periods with no ill effects in several studies. I like to use good UVB for my aquatics, but they certainly can get dietary D3 and can use that effectively.

However if using a D2 supplement, or relying on feeding plants that have Vitamin D - which would be D2 - there is a caution. In humans studies have conclusively shown D2 is not utilized well by the body. Some studies showed it had no effect on improving bone health. It also does not last long in the body as D3 does. Does this translate to tortoises? I don't know for sure, but I think it is worth insuring there is either good UVB exposure, or good quality D3 supplement in the diet. If relying on dietary D2 naturally in some plants that are fed (mushrooms can be high in D2) it would be important to not rely on that alone long term, in my opinion to be safe.

Will is the dietary Guru, so let see what @Kapidolo Farms has to add.
Thanks, Mark!:):<3:
 

Moozillion

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the D's pathways are complicated with recycling and feedback loops and genuinely unsettled among people who put much more effort into understanding it than I have.

I feel certain that mud turtles can get D3 directly from diet, my own first hand experience with this regards three stripped mud turtles living well indoors on what was called trout chow (contained D3). I do not know the ingredients anymore of those chows, but often suggest to people to use 'gold fish pellets'.

I recently heard @Markw84 narrate that cold water Koi food, if I got that right, works. If it has D3 in its formulation, it's probably going to work.
Thanks, Will!:):<3:
 

Lyndi

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It also explains why the turtles I've recently rescued are not suffering from weird shell deformities. For four years they were kept in a school as 'pets', in one tank with an old style Exo Terra light fitting which I very much doubt was replaced regularly, if at all! When I brought them home the light emitting from the tube was almost non-existent! However, as they were being fed with Zoo Med's Growth Formula pellets I guess that was making up for the lack of UVB lighting? They were also only being fed one scoop of pellets just three times a week - as the scoop is tiny and they had to share, I don't think they were being overfed either! Which brings me to another question: how often, and how much, to feed a mud turtle who is at least 5 years old? They are still on the Zoo Med pellets with the occasional dried mealworm and bits of scallop or prawn. Obviously I don't want to overfeed them but I don't want to underfeed them either, and one already eats more often and enthusiastically than the other.
 

Chubbs the tegu

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Good thread! There’s been so much debate wether certain reptiles need uvb... blue tongue skinks and savanna monitors for example just because ive owned both.. ive always used it just to be on the safe side but thats just me.
 

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