We have the results in for the Egyptian tortoise study

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We have the results in for the Egyptian tortoise study

Postby Tortoise Trust » Sun Apr 29, 2012 7:37 am

As many of you know, one of the projects supported by the Jill Martin Fund in 2011 was a field study (the first ever) of the wild diet of Testudo kleinmanni.

See: viewtopic.php?f=3&t=7920&p=70495#p70495

We now have the laboratory analyses. I will get a full synopsis up ASAP, and we'll also cover in the next newsletter.

However - this kind of study illustrates perfectly WHY this kind of fieldwork is incredibly important, and why it matters to all keepers, everywhere. The results we now have reveal some very, very interesting facts.

A brief summary:

Calcium to phosphorus levels of the wild diet in the area are astoundingly high. Far higher than even we expected. The mean Ca:P ratio of the wild diet was 14:1. You should compare this to a typical captive diet.... going by our own preliminary data from here in Spain, we suspect that wild T. g. graeca are receiving a similar level. Also take note that many "caresheets" advise diets as low as 2:1!

Fibre levels are also shown to be extremely high (33.4 to 49%). This is again consistent with our own results on T. g. graeca (http://www.tortoisetrust.org/articles/dietaryfibre.html). Compare to a typical captive diet...

Protein levels. These were broadly in the predicted range (17.3% DM basis). This roughly corresponds to a "wet basis" (fresh) intake in the 4-6% range.

Oxalic acid levels. This was where a bit of a surprise occurred. It was predicted that levels would be fairly low, based on the assumption (!) that high levels may interfere with calcium uptake... very little reliable data on this exists for reptiles. It is fairly well-studied in mammals, and generally, these results have simply been 'extended' to cover tortoises. In this field study, however, ALL OF THE PLANTS TESTED had levels of above 0.50g/100g. Most current dietary advice suggests avoiding plants above around 0.30g/100g.

This latter result requires further study, but strongly suggests that we may be over-exaggerating the effects of oxalic acid at least insofar as tortoise diets are concerned. The mammalian-herbivorous reptile association may not be a particularly accurate model in this instance.

Thank you to everyone who has supported the Jill Martin Fund. This allowed this critically important study to proceed. The knowledge gained will contribute greatly to breeding for conservation, and also is of huge relevance to keepers of tortoises as pets. The implications are very considerable.
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Re: We have the results in for the Egyptian tortoise study

Postby Carrie » Sun Apr 29, 2012 11:47 am

Most interesting. I do not have Egyptian tortoises, but do have Hermanns and this has prompted me to sprinkle more limestone flour on the earth of outside enclosures, plus keep adding limestone stones of all sizes from elsewhere in the garden! May not overly worry if they eat too many dandies! Thank you Andy.
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Re: We have the results in for the Egyptian tortoise study

Postby Nina » Sun Apr 29, 2012 12:38 pm

Thanks, Andy -- these are such interesting results, and it shows how valuable a contribution the Jill Martin Fund has made to our knowledge of tortoises!

I'm afraid I don't know enough about the actual process whereby the oxalic acid binds with calcium to prevent its uptake, but I wonder if it's possible that the sheer amount of calcium in the diet (and it would seem to be high, judging by those calcium to phosphorous levels) sort of overwhelms the oxalic acid binding process and allows uptake of at least a reasonable amount of the calcium ingested by the tortoise? And the implications of that would be that unless a tortoise has a high calcium to phosphorous ratio in its diet then plants with high levels of oxalates should still be avoided. All this is speculation from someone who knows almost nothing about the processes involved (lol -- me), but it certainly gets you thinking, and I do hope that further research is undertaken, as it could well lead to revising our current recommendations on feeding plants containing oxalic acid, and that would increase the variety of plants that we could provide as food for our tortoises.

Nina
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Re: We have the results in for the Egyptian tortoise study

Postby Tortoise Trust » Sun Apr 29, 2012 4:29 pm

One possible answer is here....

http://www.ncbi.nlm.nih.gov/pubmed/18210126

http://www.sciencedirect.com/science/ar ... 1789800569

http://www.sciencedirect.com/science/ar ... 3802000404

This is not proven in tortoises, but is one avenue that needs investigation. In this case, there may be a commensal gut bacteria present that degrades oxalates....
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Re: We have the results in for the Egyptian tortoise study

Postby Nina » Sun Apr 29, 2012 5:05 pm

Gosh, that's really interesting, and the idea of a gut bacteria that could degrade the oxalates never would have occurred to me -- thanks for those links, Andy. I know these are mammals, but the fact that the research indicated that people can adapt to high oxalate intake by producing more of the oxalate degrading bacteria, and the Indian study where people with less of the bacteria produced more calcium oxalate stones is fascinating. If there is a corresponding picture with tortoises then that really would change how we think about oxalates, and I hope that someone is considering research in this area.

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Re: We have the results in for the Egyptian tortoise study

Postby Tortoise Trust » Sun Apr 29, 2012 9:35 pm

We are liaising over the next steps.... there are several avenues to explore here. It is certainly all very interesting!
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Re: We have the results in for the Egyptian tortoise study

Postby Elaine » Wed May 02, 2012 7:59 pm

Has there been any studies done planting up a varied diet in soil and the same seeds in a soil with perhaps 50% calcium in it? Would this up the natural calcium intake within the plant?
If a plant is dried out with the days heat does this UP the level of calcium?? Don't think it would as sun kills most things at such high intensity.
With so little food about WHERE are they getting it from? These calcium levels....?
Also very interesting that the wild torts in Almeria are showing the same pattern of results.

I need to do a reread, so much information to digest.
Many thanks
Elaine
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Re: We have the results in for the Egyptian tortoise study

Postby P-A Barkskog » Sat Apr 06, 2013 5:48 pm

Tortoise Trust wrote:Calcium to phosphorus levels of the wild diet in the area are astoundingly high. Far higher than even we expected. The mean Ca:P ratio of the wild diet was 14:1. You should compare this to a typical captive diet.... going by our own preliminary data from here in Spain, we suspect that wild T. g. graeca are receiving a similar level. Also take note that many "caresheets" advise diets as low as 2:1!


How does this ratio of the food affect the ratio of the blood?
Per-Anders Barkskog, Sweden
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Re: We have the results in for the Egyptian tortoise study

Postby Tortoise Trust » Sat Apr 06, 2013 7:43 pm

Answer:

We have no idea :lol:

That will have to wait. Invasive tests of that kind can be difficult on wild tortoises, and requires special permission from the authorities (risk of contamination, etc.)
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