Well, I don't think it is true that "most captive reptiles were calcium/ phosphorus deficient ". Most are doing just fine. Maybe that's not how you intended that sentence to come out, though.
Captive reptiles that do have hypocalcemia may indeed have it due to inadequate levels of Vitamin D, since D3 is necessary for dietary calcium absorption. Many, or even most, reptiles we keep in captivity can utilize dietary D3 well (strict herbivores tend to be exceptions; they don't seem to utilize dietary D3 well). Almost all captive herp species (even nocturnal ones, since cutaneous D3 production is probably a conserved evolutionary trait) can in fact use UVB to manufacture D3. The only exception I've read about are some species of
Varanus that cannot quite make enough D3 from sunlight and need some in their diet, which they typically get in no short supply. Not all species have been studied on this, of course, not by a long shot. I personally think dietary dosing (when D3 needs to be supplemented, that is) makes infinitely more sense when possible, since it is cheap and easy and foolproof, none of which is the case with captive UVB. But that's another topic, maybe.
All of this, though, is independent of the need for a correct Ca/P ratio in food. UVB exposure will not produce calcium, and will not correct a dietary imbalance of calcium and phosphorus. All animals need a dietary source of the proper ratio of Ca and P, and also need adequate blood levels of D3 (either from the diet, or UVB, or both).
Reptiles that eat primarily whole rodent (or other whole terrestrial vertebrate) prey have no shortage of dietary D3, nor of calcium or phosphorus in a fairly acceptable ratio.
Originally Posted by Malum Argenteum
Well, I don't think it is true that "most captive reptiles were calcium/ phosphorus deficient ". Most are doing just fine. Maybe that's not how you intended that sentence to come out, though.
Stay in peace and not pieces.
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