Effects of vitamin D3 supplementation and UVb exposure on the growth and plasma concentration of vitamin D3 metabolites in juvenile bearded dragons (Pogona vitticeps)

The effectiveness of dietary vitamin D-3 and 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 D-3 supplementation (0 to 400%) or six UVb exposure times (2 to 12 h). At 3 and 6 months of age, blood samples were obtained from each animal and analysed for 25(OH)D-3 and 1,25 (OH)(2)D-3. At 3 months of age, plasma concentrations of 25(OH)D-3 did not increase with increasing vitamin D-3 supplementation unlike the 1,25(OH)(2)D-3. At 6 months of age, plasma concentrations of both 25(OH)D-3 and 1,25 (OH)(2)D-3 increased with increasing vitamin D-3 supplementation. Plasma concentrations in UVb-exposed animals were 18 times higher for 25(OH)D-3 (178.4 +/- 9.0 vs. 9.9 +/- 1.3 nmol/L) and 5.3 times higher for 1,25(OH)(2)D-3 (1.205 +/- 0.100 vs. 0.229 +/- 0.025 nmol/L) than in vitamin D-3 supplemented animals at 6 months of age. This study shows that 2 h of UVb exposure enables adequate physiological concentrations of plasma vitamin D metabolites to be maintained in growing bearded dragons. Oral supplementation of vitamin D-3 is ineffective in raising plasma concentrations of 25(OH)D-3 and 1,25(OH)(2)D-3 to concentrations observed in UVb-exposed animals. (C) 2010 Elsevier Inc. All rights reserved.