Proceedings of the Vertebrate Pest Conference

Coumatetralyl (Racumin®) has been known since 1957 as a multiple dose anticoagulant and has been used successfully over many decades. In the seventies and especially the eighties, rats developed an increased resistance to anticoagulants in certain regions of Central Europe. Also, the addition of vitamin K to animal feed (especially to chicken feed) has reduced the efficacy against rats and mice in farm buildings. Combinations of anticoagulants with different types of vitamin D are generally described to increase the efficacy of action against rodents. It was found that especially the combination of coumatetralyl with cholecalciferol (vitamin D3) could overcome the above mentioned problems. Cholecalciferol causes hypercalcemia and, therefore, has a different mode of action compared to anticoagulants. The combination of these active ingredients leads to an obvious increase in efficacy against rodents, even under difficult conditions. The formulation with optimal rodenticidal efficacy contains 0.04% coumatetralyl and 0.025% cholecalciferol mixed in rolled oats.