Exploration of Vitamin D Metabolism in Indoor-Housed Hoffmann’s Two-Toed Sloths (Choloepus hoffmanni)
Two-toed sloths are unique arboreal members of the superorder Xenarthra, in which disease related to calcium metabolism has been reported.1-3 This research surveyed multiple biomarkers of calcium and vitamin D metabolism, measured epidermal 7-dehydrocholesterol (7-DHC) concentrations in two locations, and evaluated the use of dried blood spots for the measurement of 25-hydroxyvitamin D (25[OH]D), in Hoffmann’s two-toed sloths (Choloepus hoffmanni). Samples were collected from nine indoor-housed healthy sloths during routine examinations. Serum was analyzed for 25(OH)D2/D3, 1,25(OH)2D2/D3, and 24,25(OH)2D2/D3 parathyroid hormone (PTH); ionized calcium (iCa); and minerals (calcium [Ca], magnesium [Mg], and phosphorus [P]). Full-thickness lumbar and abdominal skin biopsies were analyzed for 7-DHC. Whole blood was collected on a dried blood spot (DBS) card and analyzed for 25(OH)D2/D3.
All detectable vitamin D metabolites were analogues of D3, with mean±SD of 25.1±7.2 ng/ml for 25(OH)D3, 54.2±18.9 pg/ml for 1,25(OH)2D3, and 7.7±3.2 ng/ml for 24,25(OH)2D3. Mineral values were within expected ranges. Average PTH was 0.2±0.17 pmol/L, and iCa was 1.1±0.14 mmol/L. There was a significantly higher concentration of epidermal 7-DHC in the abdominal (184.4 ng/g) compared to lumbar (94.87 ng/g) biopsy samples (p=0.038). Statistical analysis using Passing-Bablok regression analysis, Bland-Altman plots, and paired t-test found good agreement between DBS and serum samples for measurement of 25(OH)D3, without constant or proportional bias. This research generates baseline data regarding vitamin D and calcium metabolism in Choloepus hoffmanni and provides a foundation for future research projects in this species, designed to improve husbandry and nutrition recommendations and reduce the incidence of disease conditions related to calcium homeostasis.
The authors thank Mazuri® Exotic Animal Nutrition, who provided the funding for this research, as well as the animal care staff of the Rosamond Gifford Zoo for assistance with sample collection and processing.
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