Interspecies variability in hepatic vitamin K reserves - implications for anticoagulant rodenticide sensitivity and ecotoxicological risk assessment

The extensive use of anticoagulant rodenticides (ARs) for rodent control has resulted in widespread exposure of non-target animals, with notable differences in susceptibility between species. Vitamin K reserves, which are essential for counteracting AR-induced coagulopathy, may partly explain this variability. This study assessed vitamin K status in 678 animals representing 31 mammalian and avian species. Hepatic concentrations of phylloquinone (K1) and menaquinone-4 (MK4) levels were quantified, revealing substantial interspecies variation influenced by dietary patterns and seasonal changes. Total hepatic vitamin K concentrations ranged from 6.1 ng/g in wild boar to 261.9 ng/g in common quail (wet weight basis). In mammals, K1 accounted for 63-96 % of total vitamin K, whereas birds were dominated by MK4 (81-99 %). Herbivorous mammals had significantly higher hepatic K1 than omnivorous and carnivores. Among birds, carnivorous had higher K1 than omnivores. To further explore temporal variation in vitamin K status, a seasonal analysis was conducted in red foxes. This revealed a fivefold increase in hepatic K1 concentrations during summer compared to spring, likely driven by seasonal shifts in diet composition. These findings provide new insights into the interspecies variability in vitamin K reserves and highlight their potential role in determining AR susceptibility, emphasizing the necessity of conducting species-specific ecotoxicological risk assessments.