Colchicum autumnale poisoning in a dairy farm in Switzerland: a glimpse at the milk safety aspect

Colchicine poisoning in livestock presents a significant challenge for dairy farming, particularly in regions where Colchicum autumnale (autumn crocus) is prevalent in pastures. This case report describes an incident on an organic dairy farm in Eastern Switzerland where Brown Swiss cattle showed clinical signs after consuming freshly mown meadow forage containing autumn crocus leaves. The ingestion of this highly toxic plant led to severe effects such as apathy, hypothermia, and reduced milk production, which required immediate veterinary intervention. As colchicine was expected to be secreted in the milk, the milk supplier imposed a delivery stop based on European Commission Regulation (EU) No 37/2010, excluding the use of colchicine as a pharmacologically active substance in food-producing animals. Using liquid chromatography coupled to tandem mass spectrometry, it was shown that a bulk milk sample taken 2 weeks after the poisoning event tested positive, while a further bulk tank milk sample collected 5 weeks after the incident tested negative. Milk deliveries were then resumed. This paper further reviews the current understanding of colchicine as a chemical hazard in milk and presents a toxicological assessment, which is crucial for setting a detection limit for methods aimed at detecting colchicine in milk, given the absence of maximum limits and withdrawal periods following exposure. This study contributes to raising awareness of colchicine as a milk safety concern and to improving the monitoring of toxic plant exposure in livestock management (from feed to food concept).