Best Practice Usage of Long-Acting Drenches
Usage of short-acting primer drenches at the same time as a longer acting product can greatly reduce resistance selection as the primer can remove the highly resistant adult worms that would otherwise have a long period of breeding advantage in the treated sheep whilst more sensitive worms are being excluded (for up to 100 days) .
Sheep treated with longer-acting products can be monitored after dosing to assess how much resistance selection is occurring. Such monitoring may indicate a need to administer an exit drench to remove surviving, resistant worms or at least give an indication on whether a primer dose is needed next time the same product is used2.
Speak to your local Animal Production Specialist (APS) to learn more about this issue and how to implement best practice for the usage of longer-acting products.*
![Nic Dawes (Animal Health Advisor) - applying a drench](https://www.nutrienagsolutions.com.au/sites/default/files/styles/image_2000x_/public/2023-08/images/nic_dawes_0.png?itok=RfiSzYwl)
Animal Health Advisor, Nic Dawes, applying a drench to sheep.
*Any specialised advice provided to customers will be subject to terms and conditions. Nutrien's Animal Production Specialist advice is not a substitute for obtaining your own personalised veterinary advice for your circumstances.
1 https://wormboss.com.au/tests-tools/managing-drench-resistance-sheep
2 https://paraboss.com.au/news/long-acting-worm-treatments-the-good-the-bad-and-the-ghastly/