SERUM VITAMIN D AND SELECTED BIOMARKERS OF CALCIUM HOMEOSTASIS IN ASIAN ELEPHANTS (ELEPHAS MAXIMUS) MANAGED AT A LOW LATITUDE.

An understanding of species-specific vitamin D metabolism and its role in calcium homeostasis is essential for correct diet formulation and development of husbandry protocols for managed nondomestic species. This study documented serum vitamin D metabolites and other analytes involved in calcium homeostasis in Asian elephants (Elephas maximus) managed at a latitude similar to their wild natural habitat. Serum values for 33 elephants managed at a low latitude were measured in the peak of summer, revealing low vitamin D₂ (25(OH)D₂ 2.3 ± 0.6 ng/ ml and 24,25(OH)₂D₂ 2.17 ± 0.52 ng/ml) and nondetectable vitamin D₃. Serum minerals (calcium, phosphorus, magnesium), ionized calcium, and parathyroid hormone were within normal reported ranges. In comparison with previously reported values in elephants managed at a high latitude, 25(OH)D₂ (P < 0.001), 24,25(OH)₂D₂ (P = 0.001), and magnesium (P = 0.013) were significantly lower, and parathyroid hormone was significantly higher (P < 0.001). The lack of D₃ production during ample sun exposure at a low latitude suggests that Asian elephants are incapable of cutaneous photobiosynthesis of vitamin D, and that low serum D₂ is normal for this species.