Rhinoceromics: a multi-amplicon study with clinical markers to transferrin saturation levels in ex situ black rhinoceros (Diceros bicornis michaeli)

Linda G R Bruins-Van Sonsbeek ¹ Martie C M Verschuren ² Sonja Kaal ³ Peter W Lindenburg ³ C W Rodenburg ² Marcus Clauss ⁴ Arjen G C L Speksnijder ⁵ B F.J Bonnet ⁶ Floyd Wittink ^6*

• ¹ Department Clinical Sciences, Faculty of Veterinary Medicines, Utrecht University, Utrecht, Netherlands, Netherlands
• ² Avans University of Applied Sciences, Breda, North Brabant, Netherlands
• ³ LCAB, Departments of Analytical BioSciences, University of Applied Sciences Leiden, Leiden, Netherlands
• ⁴ Clinic for Zoo Animals, Exotic Pets and Wildlife, University of Zurich, Zurich, Zurich, Switzerland
• ⁵ LCAB, Department of Environmental Metagenomics,University of Applied Scieneces Leiden, Leiden, Netherlands
• ⁶ LCAB, Department of Bioinformatics, University of Applied Sciences Leiden., Leiden, Netherlands

Iron overload disorder (IOD) is a prevalent condition in ex situ black rhinoceroses (Diceros bicornis), while this condition has not been reported in the wild. The objective of this study was to gain a deeper understanding of the relationship between 25 hydroxy vitamin D (25(OH)D), inflammatory markers, insulin levels, the gut microbiome, diet components, and transferrin saturation (TS) in ex situ black rhinoceroses; As inflammatory markers interleukin 6 (IL-6), serum amyloid A (SAA), interferon γ (IFN-γ), tumor necrosis factor α (TNF-α) were analysed. Blood and faeces of eleven black rhinoceroses from five different European zoological institutions were monitored over a period of one year. Our study corroborates the findings of previous studies, which demonstrated that insulin, inflammatory markers, and TS% are higher in ex situ black rhinoceroses compared to previously published wild ranges. Our data show no correlations were found between insulin , 25(OH)D, TS%, inflammatory markers or the shortchain fatty acids (SFCAs). Serum 25(OH)D exhibited significantly higher levels in the summer compared to the winter season. Transferrin saturation was influenced by age in accordance with previous studies. The microbiome did not differ significantly between individuals, institutions, sex or season, in contrast to the mycobiome, which differed significantly amongst institutions. Whether the difference in the mycobiome data plays a role in the physiology of the animals could not be concluded from this study. Introduction