Blood Vitamin Concentrations in Pond Sliders (Trachemys scripta) Under Human Care in Central Europe and Possible Seasonal and Sex-Specific Influences

Vitamin A deficiency is common in pond sliders, and vitamin E and B1 deficiencies have also been described in carnivorous aquatic species such as crocodiles, but otherwise little is known about vitamin concentrations in the blood of reptiles, and reference intervals only exist for a few vitamins in a few species. The aim of this study was therefore to measure vitamins A, B1, B2, B6, B9, B12, and E in the heparinized whole blood and plasma of pond sliders (<i>Trachemys scripta</i>) (<i>n</i> = 188) from April to September 2022 using high-performance liquid chromatography (HPLC) and spectrophotometry. In addition to establishing reference intervals, possible influencing factors, including the season of blood sampling and the sex of the turtles, were evaluated. The median concentrations measured were as follows: vitamin A-0.17 mg/L, B1-59.10 µg/L, B2-693.50 µg/L, B6-2.375 µg/L, B9-16.06 ng/mL, B12-3225.00 pg/mL, and E-7.59 mg/L. Significant (<i>p</i> ≤ 0.05) seasonal variations were found for vitamin A, B1, and B9, and sex-specific variations were found for vitamin E. The results show that factors such as sex and the time of year play a role in vitamin levels in the blood of turtles and should be considered when interpreting blood results. The reference intervals established in the present study serve as a basis for further studies and help to control and improve the vitamin supply of the turtles, contributing to the better husbandry and nutrition of this species in human care.