Reference concentrations of cholecalciferol in animals: a basis for establishing non‐target exposure

Abstract Cholecalciferol (vitamin D 3 ) is widely used as a vertebrate pesticide in New Zealand. However, cholecalciferol also occurs naturally in animals. Therefore, when trying to determine whether a non‐target animal has been exposed to cholecalciferol baits, knowledge of the baseline cholecalciferol concentrations in the animal's plasma and tissue is required. We analysed cattle, sheep, pig, deer, dog and cat plasma and liver samples for the vitamin D 3 metabolite 25‐hydroxycholecalciferol (25‐OHD), a sensitive biomarker for cholecalciferol. Based on these data and a literature search we present 25‐OHD reference ranges. We also examined the literature for 25‐OHD concentrations in poisoned animals and compared these to the reference ranges. Where plasma and liver samples have 25‐OHD concentrations at least four times higher than our reference ranges it is likely that the animal has been exposed to cholecalciferol baits. 25‐OHD concentrations 10 times higher than the reference range indicate ingestion of abnormally high amounts of cholecalciferol.