But that doesn't involve giving them noon-level UVI exposure 14 hours a day, as many are starting to suggest it seems..>>
I totally, TOTALLY agree with you regarding the utterly stupid suggestions that “more UV is better” and that “people should offer the animals levels equivalent to mid-day maximums quoted on weather reports from the places where these animals live”.
All my talks and writings emphasise that these suggestions are completely wrong. Climate does NOT equal microclimate! Animals should never be offered more than they would be expected to receive in good weather in their native microhabitat at the time of day that would be when they would be most likely to be out in full sunlight (for baskers) or exposed to daylight (non-baskers). For baskers, this time of day is almost always early to mid-morning. When UVI levels are low to moderate, typically somewhere between zero at dawn to around 4 or 5 at the time they start to retreat into shade. I usually say that I believe a UVI of 3.0 is good for almost all species; I have no evidence, except for the understanding that some vitD3 researchers say that human skin responds well to UVI 3.0 for vitamin D3 synthesis, without causing rapid sunburning, and that it corresponds to a typical solar level at around 8.30am in the tropics.. a time when animals are often seen basking.
Frances Baines":2z4gfy5y said:This is known to be true in human skin under a normal SOLAR spectrum, with naturally balanced levels of UVB across the UVB spectrum.
However it is NOT true when the spectrum is UNLIKE that of the sun. Back in 1982 they discovered that the exact proportions of different parts of the UVB spectrum determine the percentages of the different photoproducts produced, only one of which is vitamin D3. If a spectrum very different from sunlight is used, the photoproducts are produced in different amounts. And since it is the production of photoproducts other than D3, which limit D3 production, you can see that some spectra might hinder D3 formation, others might enhance it... and in theory, allow more to be made than would be possible under sunlight. This might even allow too much to be produced!
Some lamps have indeed seemed to cause very high vitamin D3 levels in some animals. They have not shown any toxic effects, but there seems to be no other obvious explanation for the blood test results ... unless the assays are not actually measuring vitamin D3, instead cross-reacting with one of the other photoproducts. No-one seems to know...
Taterbug":38r7eobb said:Because I have a pretty large cage I am more comfortable with offer a wider range of options - having more space and options means the lizard gets to choose not me. I offer a basking site of about UVI 5-6 and 130F basking temp as my "too hot"; it does get used in sort bursts, as does the cool areas and hides. I also have all my lights on timers so the lights dim on/off and the UV is on only when the basking lights are 100%.
Taterbug":yfgbg1tw said:I have to disagree on the point of "what's best" though, but it's purely from an idealized vantage point. T8 lamps are loosing their relivance when it comes to best husbandry practices for beardies.
Agreed, and a valid point in regards to the MBD we can actually see.Taterbug":39h584sc said:The D3 cycle and the role of it's components in the body is complicated, and I worry that it's not a clear delineation between thriving and surviving sometimes. For me, the lack of MBD is not a good baseline. MBD that we can easily identify on on sight is a devistaiting level of defficency. Not having MBD does not mean the animal has adequate D3 levels for all their systems, or that we have found the level of "just enough" UVB, (or that we haven't for that matter.)
Not too sure I agree with you on this one, although I'm admittedly on the fence on it just because I haven't done as much research into it as other aspects of this. In natural sunlight, the sun will start destroying more d3 from being produced in the skin once a certain threshold is reached. This is not true for artificial lighting, and in theory could lead to over production of D3, which of course like everything, has it's own issues.Taterbug":39h584sc said:From how I understand the D3 cycle too much (from photosynthesis) is less harmful than too little, within reason.
However it is NOT true when the spectrum is UNLIKE that of the sun. Back in 1982 they discovered that the exact proportions of different parts of the UVB spectrum determine the percentages of the different photoproducts produced, only one of which is vitamin D3. If a spectrum very different from sunlight is used, the photoproducts are produced in different amounts. And since it is the production of photoproducts other than D3, which limit D3 production, you can see that some spectra might hinder D3 formation, others might enhance it... and in theory, allow more to be made than would be possible under sunlight. This might even allow too much to be produced!
Some lamps have indeed seemed to cause very high vitamin D3 levels in some animals. They have not shown any toxic effects, but there seems to be no other obvious explanation for the blood test results ... unless the assays are not actually measuring vitamin D3, instead cross-reacting with one of the other photoproducts. No-one seems to know...
Hmm, interesting I didn't even think to ask when we were discussing this. I went back through our e mails just now and she doesn't really elaborate on that at all.Taterbug":f697542z said:How does the spectrum of Arcadia/reptisun bulbs compare in those photobiology active wavelengths. She mentions "when the spectrum is different" and "some bulbs". Are these bulbs very far off on those key wavelengths, or are they actually relatively close?
I had to think of that for a minute before feeling comfortable with giving an answer. My answer is, it would change my opinion to a degree. I would feel more comfortable with slightly higher UVI's than I feel comfortable with right now, but it wouldn't in complete essence change my thoughts. Only because their are other potential harms from higher UVI levels than just excess vit. D production.Taterbug":f697542z said:If it was shown that the wavelengths responsible for the photo regulation are intact... Would it effect your opinion?
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