The effectiveness of dietary vitamin D3and UVb exposure on plasma vitamin D metabolites in growing bearded dragons (Pogona vitticeps) was studied. A total of 84 (40 males and 44 females) newly hatched bearded dragons were allocated to six levels of oral vitamin D3supplementation (0 to 400%) or six UVb exposure times (2 to 12h). At 3 and 6months of age, blood samples were obtained from each animal and analysed for 25(OH)D3and 1,25(OH)2D3. At 3months of age, plasma concentrations of 25(OH)D3did not increase with increasing vitamin D3supplementation unlike the 1,25(OH)2D3. At 6months of age, plasma concentrations of both 25(OH)D3and 1,25(OH)2D3increased with increasing vitamin D3supplementation. Plasma concentrations in UVb-exposed animals were 18 times higher for 25(OH)D3(178.4±9.0 vs. 9.9±1.3nmol/L) and 5.3 times higher for 1,25(OH)2D3(1.205±0.100 vs. 0.229±0.025nmol/L) than in vitamin D3supplemented animals at 6months of age. This study shows that 2h of UVb exposure enables adequate physiological concentrations of plasma vitamin D metabolites to be maintained in growing bearded dragons. Oral supplementation of vitamin D3is ineffective in raising plasma concentrations of 25(OH)D3and 1,25(OH)2D3to concentrations observed in UVb-exposed animals.

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Comparative Biochemistry and Physiology. Part B: Biochemistry & Molecular Biology
Erasmus MC: University Medical Center Rotterdam

Oonincx, D.G.A.B, Stevens, Y, van den Borne, J.J.G.C, van Leeuwen, J.P.T.M, & Hendriks, W.H. (2010). Effects of vitamin D3 supplementation and UVb exposure on the growth and plasma concentration of vitamin D3 metabolites in juvenile bearded dragons (Pogona vitticeps). Comparative Biochemistry and Physiology. Part B: Biochemistry & Molecular Biology, 156(2), 122–128. doi:10.1016/j.cbpb.2010.02.008