Calcium and UV explained

[Neal]

So, the two areas related to tortoises that I have the most confusion with are calcium and UV needs. Science is by far my least favorite subject, so I'm having a hard time figuring out how these two things work. I was wondering if someone could explain it to me, and don't be afraid to get technical, if I don't understand something I'll question it.

Basically what I want to learn is: How are UV rays absorbed into the tortoise? Calcium I know is more from the food it eats, but does a tortoise have to be in direct sunlight or do UV rays just kind of bounce around everywhere even in the shade? Once the tortoise has absorbed or consumed UV rays and calcium what is happening inside the tortoise’s body with these elements? How does D3 play into the tortoises needs?

I'll start there, I have general ideas of how this all works, I'm just trying to piece together the puzzle.

 

[J. Ellis]

I am in no way a scientist or do I even play one on TV.. However, these are my thoughts on the subject..

Have you ever had sunburn? Then you have had firsthand experience of Ultraviolet Radiation. UV is produced by the sun in 3 bands ([a], (b), and [c]). It is a form of radiation the same as X rays and Gamma rays are a form of radiation. As with most radiation the ozone layer of our planet blocks/reflects 97-99%. Imagine if it only reflected 80%, we'd be cooked! Ultraviolet irradiation is the number one cause of skin collegen deterioration and the formation of cancer radicals. In example, prolonged exposure to high intensity UV bulbs like those used in tanning beds...

UV[a]; also called "long wave" is replicated through the use of a blacklight. In my experience this is the most vital form of ultraviolet rays needed. I'm by no means playing down the necessity of UV but I think that if you are unable to obtain a UV(b) bulb I don't think that it would necessarily be a dire situation.

UV(b); also called "medium wave" is replicated through the use of specific bulbs labeled as such.

UV[c]; also called "shortwave" or "germicidal" is the type of ultraviolet radiation that they use to sterilize and purify objects.

UV[a] and UV(b) are vital to de novo synthesis of Vitamin D (supplemented as D3). De novo synthesis is the breaking down of simple molecules (such as vitamin D) for better absorption into the blood, tissue, bones, eggs, etc. of the animal. Vitamin D has been proven to be a catalyst in the metabolism of calcium. Along the same lines with vitamin D is phosphorus (found in plants such as spinach). Phosphorus isn't nearly as imperative as D is, but it is also needed for complete absorption of calcium.

Thinking to scale; the metal mesh of an aquarium's screen top has enough hinderance of UV[a] and UV(b) to nearly half the amount of usable radiation getting through. With that said, do I think that there is enough usable ultraviolet in the shade? Sure! If you're outside 24 hours a day. Direct, unfiltered, unadulterated sunshine has more ultraviolet rays per square centimeter.

P.S. I have used numerous symbols to denote "b" because the forum keeps trying to bold everything! Lol

So, the two areas related to tortoises that I have the most confusion with are calcium and UV needs. Science is by far my least favorite subject, so I'm having a hard time figuring out how these two things work. I was wondering if someone could explain it to me, and don't be afraid to get technical, if I don't understand something I'll question it.

Basically what I want to learn is: How are UV rays absorbed into the tortoise? Calcium I know is more from the food it eats, but does a tortoise have to be in direct sunlight or do UV rays just kind of bounce around everywhere even in the shade? Once the tortoise has absorbed or consumed UV rays and calcium what is happening inside the tortoise’s body with these elements? How does D3 play into the tortoises needs?

I'll start there, I have general ideas of how this all works, I'm just trying to piece together the puzzle.

 

[Neal]

Thanks Josh.

Here is a more difficult question, since UV rays are measurable...how can we determine how much UV a tortoise requires to necesitate de novo synthesis? What factors affect or inhibit the de novo process (ie..level of activity, temperatures, amount of food consumed, size)?

 

[J. Ellis]

I honestly think that trying to quantitatively express the amount needed in the fields that you have outlined is impossible.. but again I will share with you my thoughts.

Regardless if I'm running around the block, swimming, or sitting; while in direct sunshine I am still being exposed to the same amount of radiation waves. Whether or not I'm full, hungry, or "just right", I'm still exposed to the same amount of radiation waves. I do not believe that if I spend 20 minutes in direct sunshine that I only get the affects for 20 minutes. Like any radiation I believe that it is absorbed into the animal, material, etc.

I would want to compare it to the effects seen in Hiroshima and Nagasaki after WWII. The radiation from the atomic bomb was absorbed into the soil, buildings, trees, etc. for many, many years. Of course the radiation of an atomic bomb is markedly more than that of a simple UV wave, but I think that the physics of it all correlates.

However, to quantify "how much is just right" is like asking what the best type of ice cream is.

Thanks Josh.

Here is a more difficult question, since UV rays are measurable...how can we determine how much UV a tortoise requires to necesitate de novo synthesis? What factors affect or inhibit the de novo process (ie..level of activity, temperatures, amount of food consumed, size)?

 

[Madkins007]

It is a really, really complicated process that involves many organs and glands, but the simple version is that calcium by itself cannot easily get into the cells of the body, you need vitamin D to 'unlock' the cell.

As you said, calcium comes from food. So do many of the other necessary elements for strong bones and shell-
- phosphorous, which is usually treated as a bad thing, but you need it as much as you do calcium- you just need less of it to make everything work correctly. The proportion of calcium (Ca) to phosphorous (P) is written as the Ca: P Ratio, and should be about 1.5:1 overall in the diet.
- iron, magnesium, and other minerals
- vitamin A and other vitamins
- water
- vitamin D can come from some food sources. There are two main forms of vitamin D- D2 and D3. D2 does not work as well or for as long, and not all animals can use it efficiently. D2 is found in fungi, mushrooms, and a few other plants, and D3 can come from oily fish, some organ meat, eggs, etc. There is no solid information about how much this form of vitamin D helps most reptiles.

Two of the main elements for healthy skeletons come from the sun in the wild-
- UV lighting. Think of UV as three colors you cannot see, so we have, in order, green, blue, purple, superpurple 1 (UVA), superpurple 2 (UVB), and superpurple 3 (UVC). Our tortoises (and we humans) need good light that includes all of the colors, even superpurples 1 and 2. (UVC is mostly blocked by the atmosphere, and since it kills things, that is probably a really good idea!)
When skin is exposed to the right wavelengths of UVB light (sort of the right shade of superpurple 2), the body absorbs it and converts it to a form of vitamin D3 the cells can use. Besides making vitamin D3, UV light also affects the pineal gland, skin, and other systems in most animals.
- Warmth. Reptiles need to be warm to effectively do much of anything, even making D3 or absorbing calcium. Much of the warmth comes from infrared light, which is just another invisible color past red.


UV and shade- Again, think of UV as a color. You can see color in shade because sunlight scatters and bounces. By the same token- colors are dimmer in shade, and there is less UV in shade. However- almost all species of tortoises do some form of basking at some times. They lay out in the sun, head stretched out and up, limbs stretched out. They may do it after a cool stretch, after a rain or cloudy week, etc. They are getting warm AND getting UV at the same time.

Most tortoises do not spend a long time in hot or direct sunlight. Too much heat, too much UV, etc. is as bad for them as it is for us. They don't sunburn but too much UV can damage the skin, young eyes, etc. We do not KNOW the dosage they NEED for health, but for humans it is estimated at about 3 15 minute exposures a week of typical summer sunlight.

(By the way, in the winter, a lot less UVB hits the northern parts of the world. Above about Boston in the US, there is not a lot of useful UVB left in the sunlight!) You should also know that UV, especially UVB, does not penetrate well through most glass or plastics. Even screen and mesh can interfere with much of it.

Does this help?

 

[Neal]

That has helped very much. Peices are coming together, the dream would be to establish some kind of formula to determine how much UV exposure and calcium a tortoise would require to mimic what it would receive in the wild. As was stated though, that type of thing is basically impossible.

As far as calcium goes, what happens when a tortoise consumes too much? Too little? Based on what I have researched, the bigger threat is too much D3 as apposed to too much calcium, is this correct?

 

[J. Ellis]

Neal,

Calcium is water soluble. So you need a "constant stream" of it into the blood system to cause any ill effects. Whatever is not used is expressed from the body in the animal's waste.

The reason that Vitamin D is such a hot topic is because it is fat soluble, so it actually builds up in the fat cells. Too much too fast can cause severe symptoms.

That has helped very much. Peices are coming together, the dream would be to establish some kind of formula to determine how much UV exposure and calcium a tortoise would require to mimic what it would receive in the wild. As was stated though, that type of thing is basically impossible.

As far as calcium goes, what happens when a tortoise consumes too much? Too little? Based on what I have researched, the bigger threat is too much D3 as apposed to too much calcium, is this correct?

 

[Neal]

So basically in general terms, I can supplement a well hydrated tortoise frequently with calcium without D3 without worrying about oversupplementing? Of course what is considered "frequently" is subjective. I'm thinking for a baby tortoise, every day sprinkle their food with a small amount of calcium.

 

[J. Ellis]

Legaleze: I am by no means a scientist or veterinarian. All of my opinions expressed are just the insane blathering of a madman.

With that being said, I don't see why not? Supplementation isn't a science, nor is it necessarily really quantitative. You could even leave a small container of calcium in the enclosure itself and let them have free access to it. However, I think you really have to try VERY hard with improper diet, improper housing, and improper lighting to have any lack-of-calcium related issues.

So basically in general terms, I can supplement a well hydrated tortoise frequently with calcium without D3 without worrying about oversupplementing? Of course what is considered "frequently" is subjective. I'm thinking for a baby tortoise, every day sprinkle their food with a small amount of calcium.

 

[Greg Knoell]

Great thread, calcium absorption requires vitamin D. You can provide all the calcium that you want but with no Vit-D it cannot be used. Almost all animals use UVB radiation to manufacture Vit-D in the skin. Dietary Vitamin D is Vit-D that is eaten and/or supplemented into the diet, not produced in the skin. Dietary Vit-D is dangerous in high doses and there has been debate weather tortoises can even use dietary vit-D at all. That is why it's important to offer opportunities for your tortoise to produce Vitamin D naturally and, IMO, never rely on dietary Vit-D exclusively.

 

[Neal]

I think I'm getting it. So the calcium gets into the tortoises system, and the only way the tortoise can benefit from it is if Vitamin D is present? The tortoise gets the vitamin D from the sun, and thats how it absorbs the calcium? If no vit-d is present than the tortoise just discard the extra calcium through urates? So, if a tortoise that is outside 24/7 is given calcium supplement it could risk an overdosage more so than one kept out of UV radiation?

So a tortoise can live in a box if given calcium with D3 and never go outside, and still be "healthy" (all other things considered)?

 

[J. Ellis]

I think I'm getting it. So the calcium gets into the tortoises system, and the only way the tortoise can benefit from it is if Vitamin D is present? The tortoise gets the vitamin D from the sun, and thats how it absorbs the calcium? If no vit-d is present than the tortoise just discard the extra calcium through urates? So, if a tortoise that is outside 24/7 is given calcium supplement it could risk an overdosage more so than one kept out of UV radiation? No; that is only if you give them a calcium or vitamin supplement containing Vitamin D3

So a tortoise can live in a box if given calcium with D3 and never go outside, and still be "healthy" (all other things considered)?

I'm sure there are tons of tortoises that have never REALLY been outside. Healthy would be a relative term. Are they alive? Sure. What is their quality of life? Are they living up to their potential? I doubt it. Man has yet to invent anything better than what mother nature has already provided.

I think as stewards of any animal (cat, dog, elephant, whatever) if we are taking them out of their natural environment and imposing our will upon them we are obligated to provide for them the best that mother nature has. It is our responsibility to ensure their health and it should be of utmost importance. This includes physical, mental, and emotional. We should provide for them a safe, comfortable home; with the appropriate environmental conditions; with stellar feed and nutrition; with no chance of being physically harmed, intimidated, or harassed; timely veterinary or medical relief; consistent schedules; attentiveness and discipline where appropriate; and amazing care. [On second note, it's the same requirements I would have for children] Notice I didn't say "to the best of your ability". If you cannot do these things, you shouldn't own the animal. Period.

 

[Balboa]

Theoretically yes, but in order to do that, you would need to monitor all nutrient levels IN the Tort AND know what they need to be to ensure that. Its much easier to give the animal the tools to accomplish this for themselves.

EDIT: LOL I was too slow, and I didn't quote so this was for Neals post not Ellis's

 

[Neal]

True, I wasn't implying that I keep my tortoises in a box or intend to at any point, I was just trying to illustrate what I was understanding so far on this topic.

 

[J. Ellis]

I didn't mean to suggest that you did. I was more posting that in order to prevent any new tortoise owner from thinking that a box, a light, and a bag full'o'calcium with D3 is all they need for a happy tortoise!

Do you think you have a good grasp on the subject now? Or do you have any more questions?

True, I wasn't implying that I keep my tortoises in a box or intend to at any point, I was just trying to illustrate what I was understanding so far on this topic.

 

[Neal]

I think I do, now its just a matter of putting it into practice and observing the results. I'm fortunate enough to live in a climate similar to the natural environment that the tortoises I keep live in. My tortoises are in a large area outdoors all year long and have all sorts of food choices so supplementing and uv exposure have never been a concern of mine, but it helps to understand it to be more well rounded I guess.

Thanks for everyone's input. If any other readers have anything else to add at all please don't hesitate!

 

[Madkins007]

A couple of points-

Excess calcium is excreted to the urinary system, which will wash it away effectively IF the animal is properly hydrated. However, dehydration is THE #1 problem with captive torts according to most respected tortoise vets. I WOULD NOT count on this process, so would never recommend daily supplementation. If your diet is low in calcium over a week for some reason, add a pinch or so a week or maybe twice a week, but I would not push it- more is not always better.

We get really calcium happy as tortoise keepers, but for every good thing, there is usually a bad. Calcium inhibits iron absorption, and they need iron as well. It is so much better and safer to just aim for a proper balance.


Excess D- oddly enough, you CANNOT overdose on vitamin D from the sun- there is a 'cut off' system in place to prevent that. I do not know if it works correctly under UVB light, but it should. You CAN overdose on dietary D3. It is not really easy to do, but if you have light-based D, calcium and D, and vitamins with D and offer it all every day, it can happen over time.

We also need to remember that solar UV (UVA and UVB) offers other benefits that are harder to quantify- better color-balance for reptile eyes (which can see into the UV range), stimulation of the pineal gland (which affects sleep and growth cycles), more natural reported behaviors, etc.





(Completely off topic- your sig about the clock... I always laugh when I see that! It sounds so good, but when you realize that it is only right for 2 minutes out of the 1440 minutes a day, or 1 time in 720, the odds ain't so hot! )

 

[Neal]

(Completely off topic- your sig about the clock... I always laugh when I see that! It sounds so good, but when you realize that it is only right for 2 minutes out of the 1440 minutes a day, or 1 time in 720, the odds ain't so hot! )

But, if you are wrong that much it is VERY encouraging. As a married man, I am encouraged by this quote.