Schildkröten im Fokus
, Bergheim 11 (4) 2014: 15–21
Futterreste könnten auch nützlich sein?! Ein Diskussionsbeitrag zu Vitamin D
Text und Fotos von Hans-J. Bidmon, Düsseldorf
Food remains may be beneficial? A discussion focussed on vitamin D
Text and photos by Hans-J. Bidmon, Düsseldorf, Germany
The aim of this discussions is to raise the awarness for the various routes for the supply of essential nutrients in the light of ongoing discrepancies between biological and physical constraints addressing different important aspects of tortoise biology and nutrition. One of these discrepancies referes to the natural routes of vitamin D supply, because the comparatively thick keratin layers of the carapax scutes and the tight arrangements of scales on the skin as well as their pigmentation limit vitamin D synthesis by UVB irradiation. Furthermore the current literarature points to strict limitations of sun exposure within the natural habitats in order to protect from overheating. Therefore tortoises may have problems to gain their supply of vitamin D only through exposure to sunlight. However, according to the most current literature in veterinary medicine, vitamin D levels in European tortoises seem to be comparatively high which indicates that high natural vitamin D blood levels seem to be beneficial to their normal physiology. The remaining question how they may achieve their high blood levels of vitamin D under natural conditions is still not known. However, the answer to that question may be already present in the current literature for herbivorous animal nutrition referring to the important role of fungi and various types of molds in UVB irradiation-induced vitamin D production. Since the growths of molds depends on substrate quality, humidity and time, the time during which food remains may remain in an animal enclosure in which they are exposed to UVB irradiation may be one important aspect for the nutrition of herbivorous tortoises in regard to their vitamin D supply and mineral homeostasis in oder to prevent metabolic bone disease and other related physiological impairments. These important aspects of herbivorous reptile nutrition should be an important topic for future research in animal nutrtion and zoo biology.
Repilia: Testudines, Testudinidae, reptile nutrition, vitamin D, mold, fungi, chelonian, tortoises, metabolic bone disease, zoo biology.
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Hans-Jürgen Bidmon, Düsseldorf, Germany
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