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Nijboer, J., van Brug, H., Tryfonidou, M. A. & van Leeuwen, J. P. T. M. (2003) UV-B and vitamin D3 metabolism in juvenile Komodo dragons (Varanus komodoensis). Fidgett, A., Clauss, M., Gansloßer, U., Hatt, J. .-M. & Nijboer, J. (Eds.), Zoo Animal Nutrition II Fürth. 
Resource type: Book Article
ID no. (ISBN etc.): 3930831511
BibTeX citation key: Nijboer2003a
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Categories: Englisch = English
Keywords: Reptilien = Reptiles, Ultraviolett = Ultraviolet, Vitamin D = Vitamin D
Creators: van Brug, Clauss, Fidgett, Gansloßer, Hatt, Nijboer, Tryfonidou, van Leeuwen
Publisher: Filander Verlag (Fürth)
Collection: Zoo Animal Nutrition II
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The aim of this research project was to assess the vitamin D status in juvenile Komodo dragons held in captivity in Rotterdam Zoo. In addition, the effect of interference with UV-B on the serum levels of vitamin D metabolites and on the serum calcium concentrations were investigated in three Komodo dragons. Supplying 450 IU vitamin D3 /kg feed orally did not increase 25-hydroxyvitamin D3 (25(OH)D3 ), the 24-hydroxylated metabolite of vitamin D (24,25(OH)2D3 ), 1,25-dihydro-xy-vitamin D3 (1,25(OH)2D3 ) and calcium levels. In contrast, exposing the Komodo dragons to UV-B altered the levels of vitamin D metabolites. The amount of 25(OH)D3 increased in komodo dragon 1 (K1) (18 to 195 nmol/ml) and in komodo dragon no 2 (K2) (31 to 291 nmol/ml). The amount of 1,25(OH)2D3 did not change significant-ly in both komodo dragons (139.5.6 to 235.3 pmol/l). Measurement of 24,25 (OH)2D3 in K2 showed a dramatically improvement after exposing to UV-B; the amount of 24,25(OH)2D3 rose (7.5 to 448.1 ng/ml). Komodo dragon 3 (K3) was send to Gran Canaria where it received natural UVB. The level of 25(OH)D3 improved from 18 to 272 nmol/l. The amount of 1,25(OH)2D3 did not increase either. In all komodo dragons the calcium level remained stable and within the range 3.18 to 4.44 mmol/l. The present study docu-ments for the first time the levels of three vitamin D3 metabolites and their regulation by UV-B in Komodo dragons. According to literature low levels of 25(OH)D3 have caused bone defects in juvenile Komodo dragons. The current data show a clear effect of UV-B on the 25(OH)D3 levels and a concomitant rise in serum 24,25(OH)2D3 levels while 1,25(OH)2D3 levels remained con-stant. Although we have no data on the bone metabolism in our 3 Komodo dragons it is tempting to speculate in view of the published improvements of bone after UV-B treatment, that 24,25(OH)2D3 is involved in bone metabolism in Komodo dragons. This would be in line with data obtained in chicken and human showing a positive effect on bone. Measure-ments of a UV-B radiating lamp show that the amount of UV-B declines rapidly over time. The decay rate also differs from lamp to lamp. If “UV-B” lamps are used for synthesising vitamin D3 through the skin the UV-B radiation should be measured regularly and the lamp should be replaced before the UV-B radiation is too low for synthesising purposes. This study, although preliminary, clearly shows there is a dramatic change in vitamin D metabolites in juvenile komodo dragons using UV-B light, as compared with offering a dietary vitamin D supplement.
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