Quarantine all cattle that are new to the property, as many will carry resistant worms. Reduce the number of resistant worms that may be brought on farm by treating new cattle on arrival with a quarantine drench. Quarantine treatments contain as many active ingredients as possible, best done by using multi-combination drenches. Do not mix different drenches together unless the label states you can, or under veterinary advice, as different products may be incompatible and could harm treated animals. It is safer to use a commercially prepared combination product.
Ideally hold the treated cattle in yards, or a paddock that has recently had cattle, so that resistant worms surviving the quarantine treatment will either die by drying out in the yards, or be diluted by susceptible worms in the paddock (see the section on refugia). Monitoring through WECs will confirm the quarantine drenching has been successful.