Anticoagulant rodenticide toxicity is caused by ingestion of anticoagulant rodenticides or by over supplementing horses with warfarin, often used for managing navicular disease in horses. There are two main categories of anticoagulants which differ in their toxicity:
- First-Generation Anticoagulants: The chemicals most commonly used are warfarin, chlorophacinone, and diphacinone. These usually require multiple feedings to induce poisoning, with concentrations ranging from 0.025 to 0.005%.
- Second-Generation Anticoagulants: The most commonly found chemicals are brodifacoum, bromadiolone, and difethialone. This are generally much more toxic, killing the rodent in a single feeding and are much more biologically active.
Upon ingestion, anticoagulants inhibit epoxide reductase which reduces the ability for the horse to regenerate vitamin K. As the remaining vitamin K depletes, it will lead to inhibition of coagulation synthesis. Depending on the amount of poison ingested, there will be a delayed onset of clinical signs of toxicity. Clinical signs are often vague and general.