A ‘drench’ refers to any anthelmintic (anti-worm) product, whether it is given by the pour-on, oral or injectable route.
If worms are present and treatment is needed, the annual program for your region provides a guide as to which class of stock are most susceptible, and the best time to drench them to prevent worm numbers from rising.
Figure 1. Observing signs such as scours on the tail and back legs may indicate a worm drench would be beneficial. Image courtesy of Jenny Cotter
For stock in less susceptible classes, drenches should only be given once the need for treatment has been established, such as noting poor weight performance, following high faecal worm egg counts (WECs), after a post mortem, or observing signs such as scours or anaemia. The practice of drenching all cattle according to the calendar, or when mustering for other management practices leads to over-frequent drenching, a key cause leading to the build-up of resistance.
The decision to treat should be based on cattle management type, class of stock the history of the mob and the farm, as well as known patterns of worm presence.