Which drench is best?

14 May 2015

Following last week’s article on understanding when to drench sheep, Friday feedback now looks at determining "which" drench to use.

To recap, the three fundamentals of drenching sheep for worm control are:

  1. Do I need to drench – and if so, when?
  2. Which drench to use?
  3. How to drench?

Supported by MLA, WormBoss helps producers understand internal parasites to avoid potential resistance and negative impacts on productivity.

When answering the second question – deciding which drench to use – WormBoss suggests integrating the following principles where possible:

  1. Use drenches most effective on your property: ideally use those shown to reduce worm egg counts by at least 98% as shown by a DrenchTest. If drench effectiveness is unknown, conduct a DrenchCheck-Day10 after drenching. The more effective a drench is, the fewer drench-resistant worms will remain in the sheep after treatment.
  2. Use a combination of two or more drench groups: the chance of a worm being resistant to all active ingredients in the combination is much lower than for each individual active on its own.
  3. Use short-acting treatments: restrict the use of persistent products for specific purposes and high worm-risk times of year. There is little need to use mid-length or long-acting treatments if sheep are being moved to low worm-risk paddocks.
  4. Rotate* among all effective drench groups each time a mob is drenched (and for each paddock). An effective drench from a different group may kill worms that were resistant to the last treatment. These may be worms that survived treatment in the sheep or were picked up from the paddock.
  5. Choose a drench with an appropriate withholding period (WHP) and export slaughter interval (ESI) according to the time left before the sheep may go to slaughter.

*When rotating drenches, the current drench would ideally exclude any groups that were used the previous time. However, in practice, ensure the current drench has at least one effective active from a drench group that was not used the previous time.

Want to know more?

 Visit the WormBoss website 

Next week Friday feedback will cover the final question: “how to drench?”

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