why pre-alpin food?

[EJ]

Why don't you feed cactus anymore?

Originally Posted by Kirkie

Oh ok. It reminded me of the original Pre Alpin testudo product but with added vitamins and minerals. Not sure about the added cactus though. I don't feed cactus anymore.

[Kirkie]

I read a paper on the possible use of opuntia as a fodder crop. Its another one of those plants where the high calcium content is accompanied by a high oxalic acid content. The paper said most of the calcium was bound up in calcium oxalate.

I was only feeding it occasionally but don't really bother now. The pre alpin allows me to suppliment calcium in known measures. I do any supplimentation via this stuff now.

[Geomyda]

Originally Posted by Kirkie

I read a paper on the possible use of opuntia as a fodder crop. Its another one of those plants where the high calcium content is accompanied by a high oxalic acid content. The paper said most of the calcium was bound up in calcium oxalate.

I was only feeding it occasionally but don't really bother now. The pre alpin allows me to suppliment calcium in known measures. I do any supplimentation via this stuff now.

Thanks, have you got a reference for this paper? I too, have been worried about the high content of Oxalates in these plants and have wondered if indeed the Calcium is bound up such that it is not metabolized in the gut of Tortoises.

[Kirkie]

Hi Paul,

I'll answer in the form of a Q&A I posted on the TT forum. The response is from Andy Highfield. I'm sure cactus is ok in moderation, like most things. With me it just doesn't fit the dietry regime I'm providing these days. In the context of the grassland gold diet I mentioned, if that is a staple diet, would you want to be routinely feeding cactus?

Q. I've been doing a bit of reading on Opuntia and I've found several references to the high Calcium content but that it is present as calcium oxalate which is neither highly soluble nor easily absorbed through the intestinal wall rendering the nutrient biologically unavailable.

This is mainly in reference to human consumption but I did find a very detailled article here:

http://www.fao.org/DOCREP/005/Y2808E/y2808e0e.htm

I've always fed Opuntia both for the perceived calcium content (which I attempt to enhance by supplimenting the growing medium) and for the raw fibre content.

I know this forum has a few cactus experts, any thoughts on this and whether Opuntia is a valid calclium source for tortoises?

A.

Dave,

See also:

http://www.znaturforsch.com/ac/v58c/s58c0812.pdf

http://books.google.co.uk/books?id=e_bI ... ia&f=false

So, yes - some of the Ca in Opuntia is in the form of calcium oxalate. What it is important to note, however is:

1) The gross levels of Ca are extremely high, and the base level of P is very low. This is good.
2) We do not know for sure how well tortoises extract C from various types of plants. In short, we do not have reliable data on how efficient they are at this. It is assumed that high levels of oxalates inhibit bioavailability, but we do not know for certain. Indeed, this hypothesis is being challenged by more recent work:

http://jn.nutrition.org/cgi/content/full/129/1/170

3) Even if bioavailablity is reduced, it is not nullifed completely, and given the high base figures we start with, it would seem obvious that Opuntia would still represent a very good, useful source.

4) There are many other nutritional benefits from this plant: ultra high fibre, good moisture content, good general mineral content, protein in the 1-2% (wet) and <8% (DM) range. More or less perfect "on target" for a desert tortoise diet.

5) Empirical evidence (observations of the results of use) suggest tortoises do extract significant amounts of useful C from it. It forms quite a high percentage of the diet of wild tortoises in many arid areas. Other species also utilise it extensively:

http://www.desertmuseumdigitallibrary.o ... sseliniana

(the reference this is from, on the Ecology of the Sonoran Desert, is a superb book, incidentally! We have it here in our library).

Consequently, used as part of a balanced diet, my view it is that it is very useful indeed. I'd never recommend feeding anything exclusively or in excess. Balance and variety remains the key.

[Geomyda]

Interesting replies:
However, whilst I too would not have a problem with its use in moderation. I sense that there are many whom may have taken earlier references about the total Calcium content of Opuntia as an indication that it is a significant source of this mineral in the Tortoise diet.
My overall concern is that this may well be inaccurate, and at worst, may even be harmful:http://www.tortoisetrust.org/articles/Feeding_FAQ.htm
Oxalate Reduces Calcium Availability in the Pads of the Prickly
Pear Cactus through Formation of Calcium Oxalate Crystals
MICHELE M. MCCONN AND PAUL A. NAKATA*
USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics,
Baylor College of Medicine, Houston, Texas 77030-2600
The pads (nopales) of the prickly pear cactus are considered to be a good source of minerals and
other nutrients on the basis of compositional analysis. In this study, this analysis is taken a step
further by assessing the availability of selected minerals in nopales using an in vitro digestion and
dialysis method. The results obtained suggest that although nopales are enriched in a number of
minerals, their tissue calcium is not freely available. Microscopic analysis, energy-dispersive X-ray
microanalysis, and oxalate measurements suggest that this reduction in available calcium is a result
of its sequestration in the form of calcium oxalate crystals. The issue of mineral availability in plant
foods is important when the dependence of many populations around the world on plant foods as
their main source of minerals and other nutrients is considered.
KEYWORDS: Availability; calcium; crystals; nopales; oxalate; prickly pear
INTRODUCTION
Prickly pear cactus, from the genus Opuntia, is considered
to be an important nutrient and food source in many parts of
the world (1, 2). Mexico, Chile, Italy, and a number of areas in
the United States farm prickly pear for commercial purposes
(2). Both the prickly pear leaves (nopales) and fruit (tuna) are
consumed. In addition to a food source, nopal is also a staple
in traditional medicines. The leaves have been consumed as part
of traditional treatments of arteriosclerosis, diabetes, gastritis,
and hyperglycemia (1, 2). Several studies have investigated the
usefulness of this plant in the treatment of various ailments (3-
10).
Edible cactus has been gaining popularity in the United States
as well as other parts of the world (2). Nopal can be purchased
year-round in local grocery stores and ethnic markets. As a
vegetable, nopal is eaten fresh in salads, soups, and casseroles
as well as grilled and fried. With the increase in production
and consumption of prickly pear there has been an interest in
establishing the nutrient and mineral composition of the edible
tissue (2, 11, 12). Composition analyses have shown that edible
cacti often contain an abundance of protein, vitamins, and
minerals (2, 11, 12). To our knowledge, however, there has not
been any investigation into the availability of minerals in this
plant. Calcium availability in cacti needs to be investigated as
certain cacti have been shown to contain the antinutrient oxalate,
which can render calcium and possibly other minerals unavailable
for nutritional absorption by humans (13, 14) and other
animals.

[Kirkie]

Interesting.

I had a prickly pear taco last year, I feel ok. Urates normal.

[Geomyda]

Originally Posted by Kirkie

Interesting.

I had a prickly pear taco last year, I feel ok. Urates normal.

This paper is also interesting and recommended reading:

The Metabolism of Oxalic Acid*
Mahmut ÇALISKAN
Mustafa Kemal University, Department of Biology 31040 Hatay-TURKEY
Received: 16.11.1998
Turk J Zool
24 (2000) 103–106
© TÜBITAK
103
Abstract: Oxalic acid is a widely occurring natural product of animals, plants and other organisms. It sometimes occurs as a free
acid, but more commonly as a calcium salt. Organisms exhibit various levels of oxalate content which even show fluctuations among
the organs of the same individual. Although oxalate seems to engage in the metabolism and adaptation of animals, plants and fungi,
its mechanism is far from being completely understood. There is now an appreciable body of information regarding the occurence
and significance of oxalic acid in living tissues but the data are widely scattered in various scientific areas due to the broad distribution
of oxalate among organisms. It is my goal in the present review to gather this information together to make it available for
forthcoming research in the area of oxalate.
Key Words: Oxalate metabolism, Oxalate pathogenic activities, oxalate oxidase.