Cane toad (Rhinella marina) vitamin A, vitamin E, and carotenoid kinetics

Citation

Freel TA, Minter LJ, Smith D, Koutsos EA, Tollefson TN, Ridgley FN, and Ange-van Heugten KD. 2019. Cane toad (Rhinella marina) vitamin A, vitamin E, and carotenoid kinetics. In Brooks M, Freel T, Koutsos E Eds. Proceedings of the Thirteenth Conference on Zoo and Wildlife Nutrition, Zoo and Wildlife Nutrition Foundation and AZA Nutrition Advisory Group, Saint Louis, MO.

Abstract

Approximately 33% of the total free-ranging amphibian species are threatened. Due to this threat of extinction, the nutrient requirements of all amphibians held within human care are of vital importance. Of these, vitamin A, vitamin E, and carotenoids are of particular interest because of their connection to breeding success and because of the deficiency symptoms that have been described when amphibians are kept under human care. To properly manage amphibian species under human care, management professionals need to know how to adequately care for them nutritionally. Therefore, determining normal circulating concentrations of vitamins A, E, and carotenoids in amphibians is vital so that we can better assess their health status. This research examined the kinetics of vitamin A, vitamin E, and carotenoid concentration changes in the liver and blood of free-ranging cane toads (Rhinella marina) as they adjusted to human care while being fed two different diets. The study included 65 adult cane toads (57.8) and took place over a four-month time period with sampling periods at days 22, 50, 81, and 119 days under human care. Diet treatment 1 consisted of Mazuri® Hi Calcium Gut Loading Diet fed to feeder brown house crickets (Acheta domestica) supplemented with small quantities of fresh sweet potato and carrots. Diet treatment 2 was the same feeder cricket diet except with vitamin A and vitamin E supplementation removed and with no produce supplementation. Results found that there were significant differences (P<0.05) between the free-ranging populations for vitamin A (retinol at 87.7±16.12?g/g), vitamin E (?-tocopherol at 9.2±0.54?g/g), and carotenoids (e.g. ?-carotene at 6.1±1.37?g/g) and the toads kept in human care. Concentrations decreased over time in human care for all nutrients, despite dietary supplementation. The novel results from this study imply that additional diet supplementation may be needed for cane toads in order to keep up with their nutrient concentrations from their free-ranging diets. Using the cane toad as a model for these nutrient values can help other amphibian species by providing comparative data.

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