Blood Vitamin Concentrations in Managed Hermann's Tortoises ( Testudo hermanni ) in Central Europe and Possible Seasonal and Sex‐Specific Influences

ABSTRACT Background Vitamins are important for the health and metabolism of living organisms, but little is known about the physiologic blood vitamin levels of tortoises. Objectives The aim of this study was therefore to measure vitamins A, B 1 , B 2 , B 6 , B 9 , B 12 , and E in blood samples of Hermann's tortoises ( Testudo hermanni ). Methods Vitamin concentrations were measured in heparinized whole blood and plasma of 522 Hermann's tortoises from May to September 2022 using high‐performance liquid chromatography (HPLC) and spectrophotometry to evaluate possible seasonal and sex‐specific influences on the blood vitamin concentrations and to establish reference intervals for these vitamins in Hermann's tortoises. Results The measured median concentrations were: vitamin A 275.00 μg/L, B 1 42.40 μg/L, B 2 483.00 μg/L, B 6 4.26 μg/L, B 9 13.24 ng/mL, B 12 933.20 pg/mL, and E 2.50 mg/L. Significant ( p ≤ 0.05) seasonal variations were found for vitamins A, B 1 , B 2 , B 6 , B 9 , B 12 , and E, and sex‐specific variations for vitamins A, B 1 , B 2 , and E. Conclusions The established reference intervals serve as a basis for health monitoring and for further studies on possible deficiencies or oversupply and their clinical significance. In addition, it was shown that the season of sample collection and the sex should be considered when interpreting blood vitamin levels in tortoises.