Episode 107 – The drench resistance wake-up call
The episode is dedicated to the late Dr Dave Leathwick, AgResearch parasitologist, scientist and champion for the battle against drench resistance.
A closer look at drench resistance in dairy systems highlights how rapidly conventional parasite control methods are becoming less effective and why farmers need to take a more strategic approach. WormWise programme manager and veterinarian Ginny Dodunski unpacks the latest data and on-farm observations, explaining what drench resistance is, how it develops over time, and why it can remain hidden until it starts affecting animal performance.
Host:
- Anne Lee, Senior Journalist, Dairy Country
Guest:
- Ginny Dodunski, Programme Manager, WormWise
Using recent research and real-world examples, Ginny outlines the increasing presence of resistant Cooperia and Ostertagia in young cattle, including cases where commonly used combination drenches are no longer doing the job. She discusses how drench selection, frequency, and inconsistent dosing, particularly with pour-on products, can contribute to resistance, and why early and accurate testing is essential to understand what is happening onfarm.
The discussion also turns to practical ways farmers can reduce reliance on drenches. Ginny highlights the importance of pasture management, calf nutrition, and grazing strategies in lowering worm challenge. She explains why reducing exposure to worms in the first place can be more effective than trying to treat them later. Alongside the science, she reinforces the value of good decision making and working alongside vets to build more resilient, future proof farming systems.
New Wormwise Handbook:
https://beeflambnz.com/knowledge-hub/PDF/wormwise-resource-book.pdf
Pamu case studies:
Wormwise resistance report:
