FOOD SUPPLEMENTS
Bruce Maclean B.V.M., M.R.C.V.S.
I am writing to comment on Val and Bob Davies' comments in the latest newsletter on vitamin and mineral supplements. As a veterinary surgeon dealing full-time with exotic animals, by far the most common problems that I see are related to nutritional osteodystrophy (essentially calcium:phosphorus imbalance, whether due to direct dietary imbalance or vitamin D3 lack). While I have to say that I have never been presented with Dendrobatids with this problem, I have seen it in a huge variety of reptiles and amphibians, and I would like to make a few comments.
Certainly in most - if not all - cases we do not really have a good idea of requirements. The figure of between 1:1 and 2:1 for the calcium:phosphorus ratio is often assumed, and appears to have reasonable theoretical backing (i.e. in some cases, admittedly mainly mammals, where it is known it falls within this range). So if we take this as something to aim for, we next need to consider what the food is providing.
Crickets seem to be the food animal where most work has been done, and they are also the most commonly fed food insect (in my experience). The basic Ca:P ratio of un-treated crickets is of the order of 0.125:1, i.e. wildly imbalanced. This brings up the fact that crickets absolutely must be supplemented. It should also be noted that the many products on the market with Ca:P ratios of 2:1 (often advertised as having the correct balance) are completely useless for this purpose, as they do nothing to correct the basic imbalance in the crickets. What is necessary (bearing in mind that there is a lot higher mass of cricket than there is of supplement) is a supplement containing much more calcium than phosphorus, used every feed.
While different people have different experiences and different things that work for them, I have to say that in my experience the supplement that produces least cases is Nutrobal (Ca:P of 46:1, plus vitamin D3 supplement plus multi-vitamins). This is a very high potency supplement, and I would perhaps theoretically recommend its use in alternate feeds with a pure calcium powder such as Naturcal, although I have myself seen no cases of overdose problems associated with daily use. It may also be of interest to note the results of a recent study I carried out by Mr. Chris Gardner at the Royal Veterinary College in London, comparing Ca:P ratios in crickets after treatment with various proprietary preparations. Essentially the conclusions were that the gut-loading preparations did not seem to work very well at all, achieving ratios of around 0.7:1 or less at feeding time, falling to around 0.15:1 or less after two days. By contrast, dust-on preparations came out well; feeding time ratios of from 6:1 to 7:1 only fell to 3.5:1 (Naturcal) or 0.9:1 (Nutrobal) after 48 hours.
These figures do not of course consider the vitamin D3 content, a complicating factor in the picture. Again, requirements are virtually unknown, as are the effects of ultraviolet light. My standard advice is that a full-spectrum tube is advisable for most diurnal reptiles and amphibians, but this is more for the behavioural effects of (mainly) the UV A than the doubtful vitamin D3 synthesis stimulus. Incidentally, with regard to cheaper tubes, Activa 172 tubes retail around £15 and in my experience do have the desired effects - I use them in my hospital.
I do have to stress that the above is a very simplified picture, and based largely on experience of seeing a lot of problems with various approaches (though if anyone is interested, I can provide references for the figures given) - I would be interested in any opposite (or supporting) views.
Incidentally, one last comment. The "impressive" list of ingredients for Reptavite according to Bob Davies is per kg: Ca and vitamin D3 contents are actually less than the Cricket Plus mentioned earlier in the article.
Anyway, I hope this is helpful information - as I said, I would be very interested to hear any other views, so that I can provide the best possible advice to my clients.
Editor's note: Bruce can be contacted at the Avian and Exotic Veterinary Centre, Kelperland Veterinary Centre, Ascot Road, Touchen End, Nr. Maidenhead, Berkshire SL6 3LA.
I have the privilege (being the Editor!) of reading articles for the Newsletter perhaps months before production. Such was the case with this one. As a result, I changed from Cricket Plus, my normal food additive, to Nutrobal. It could be coincidence, but my D. imitator have started to spawn with a vengeance and have produced their first viable tadpole that is growing very quickly, and my Phelsuma dubia (under Activa 172 lighting) have produced twins in one of their eggs!