The WormBoss Drench Decision Guides will provide you with recommendations on when to drench as well as what length protection drench may be required.
The specific drench group and/or active is not recommended as this will be quite specific to your property, depending on:
To assist you to find out more about drenches (including withholding periods and export slaughter intervals), go to the Drenches section on the WormBoss web site where you can search on the type of worms and other parasites you want to target, drench groups and actives, and on drench product names.
Use all 3 principles where possible.
They are equally important and greatly slow the development of drench resistance.
A small benefit can be gained by rotating drench groups providing you also rotationally graze stock across the property so that paddocks are exposed to sheep that have received different drenches. However, if you set-stock, drench rotation will not slow the development of drench resistance.
While not affecting resistance, it is essential to choose a drench with an appropriate withholding period (WHP) and export slaughter interval (ESI) according to the time left before the animals may go to slaughter, or their milk may be used for human consumption.
Search for drenches based on the worms or other parasites targeted, drench group or active and product name.
Follow all 5 principles where possible:
1. Avoid unnecessary drenching, especially:
2. Calibrate drench guns to ensure the correct dose is delivered.
3. Calculate the dose based on the heaviest animals in the mob. Split mobs for drenching if there is a large weight range, so that heavy animals are not underdosed, and light animals are not overdosed.
4. Follow the label instructions to ensure correct dose and use of treatments.
5. After animals have been drenched, graze them initially on paddocks already contaminated with worms, not on paddocks that are being specifically prepared as low worm-risk. Eggs deposited on pasture from surviving drench-resistant worms in the animals will be diluted by eggs and larvae already on the paddock (these should be susceptible, or at least, less drench resistant).
If animals must be drenched onto low worm-risk paddocks, such as lambing, weaning or winter weaner paddocks, do both of the following:
i. When the sheep eventually leave these low worm-risk paddocks, treat them with an effective drench that is from a different group to the drench used when the sheep first went onto the paddock. The aim is to remove any drench-resistant worms surviving in the sheep after the first drench.
ii. Ensure that the next time the paddock is grazed it is with a different mob of sheep. This second mob should have a moderate to high worm burden and their last treatment must be different from the treatment used on the first mob that grazed the low worm-risk paddock. This will dilute drench-resistant worms already on the paddock with more susceptible worms that the second mob is carrying. Note that grazing with cattle will not dilute the proportion of drench-resistant worms, but they will decrease the total number of worm larvae on this paddock.