Abstract

Clinical cases of calcium and vitamin D homeostatic disturbances with secondary nutritional hyperparathyroidism were identified in a group of bottlenose dolphins (Tursiops truncatus) managed under human care. There is limited information in the scientific literature regarding normal values for vitamin D metabolites in dolphins, and ionized calcium and parathyroid levels have not been previously reported.^1,2 To better understand these variables in dolphins, blood samples were collected from 30 managed collection dolphins (50% female, mean ± SD age = 26 ± 12 years) and 19 free-ranging dolphins living in Sarasota Bay, Florida (63% female, mean ± SD age = 13 ± 9 years). Samples were analyzed for 25-hydroxyvitamin D₃ (25-OHD₃), 1,25 hydroxyvitamin D₃ (1,25-OHD₃), 1,25 hydroxyvitamin D₂ (1,25-OHD₂), ionized calcium (iCa), parathyroid hormone (PTH), and plasma biochemistry analytes. The managed dolphins had lower 25-OHD₃ (259 ± 92 vs. 598 ± 240 nmol/L, respectively; p < 0.001) and higher PTH (11 ± 8 vs. 3 ± 3 pmol/L, respectively; p < 0.001) compared to Sarasota Bay dolphins. There was no difference in ionized calcium levels (1.2 ± 0.1 vs. 1.2 ± 0.2 mmol/L, respectively; p = 0.51). When six managed collection dolphins were fed more fish species from the Gulf of Mexico with higher vitamin D for three months, 25-OHD₃ levels successfully increased and elevated PTH levels decreased.³ These findings suggest that managed dolphins can have lower than optimal dietary vitamin D, which is correctable with the addition of fish species typically eaten by free-ranging dolphins.⁴ Further investigations are warranted to continue optimizing dolphin diets and supplementation.

Acknowledgements

The authors would like to thank Sacha Stevenson, Risa Daniels, and Mark Baird for their contributions with coordinating sample collection and data analysis. Funding for this study was provided by the Office of Naval Research (ONR Grant Number N000141210294, IACUC #101-2012). Samples from free-ranging dolphins in Sarasota Bay were collected through the support of Dolphin Quest and the Office of Naval Research, under National Marine Fisheries Service Scientific Research Permit No. 15543.

* Presenting author

Literature Cited

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2.  Slifka K, Crissey SD, Kahn S, Moser A, Chen TC, Mathieu J, Holick MF. Nutritional status in captive bottlenose dolphins (Tursiops truncatus). In: Proceedings from the AZA Nutrition Advisory Group 4th Annual Conference. Orlando, FL, USA; 2001: 151–157.

3.  Slifka KA, Wells RS, Ardente AJ, Crissey S. Comparative diet analysis of fish species commonly consumed by managed and free-ranging bottlenose dolphins (Tursiops truncatus). The Internet Journal of Veterinary Medicine. 2013;10(1):1–7. ISPUB.com/IJVM/10/1/1582

4.  Venn-Watson S, Stevenson S, Parry C, Daniels RD, Baker E, Meegan J, Holick M, Jensen E. Investigation of fish-based nutrients to protect against insulin resistance in bottlenose dolphins (Tursiops truncatus). In: Proceedings from the IAAAM 45th Annual Conference. Gold Coast, Australia; 2014.