An ineffective drench allows some worms to survive, carrying the genetic code for resistance. It’s like giving them a "get out of jail free" card, enabling them to pass this trait to their offspring. Over time, resistant worms gain a breeding advantage, making it crucial to ensure your drench is highly effective at eliminating worms in your sheep.
How to Test Drench Effectiveness
There are two ways to assess whether your drench is doing its job:
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Drench Efficacy Test – This evaluates all available drench actives and combinations but does not account for how well drenches are administered.
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Drench Check – A simpler test using faecal egg counts (FEC) before and after drenching to measure effectiveness.
Ensuring Proper Drenching
To maximise drench performance:
- Dose based on the heaviest animal in the group.
- Use drench guns that accurately deliver the correct amount.
- Ensure each sheep swallows the full dose.
Running a lamb drench check
A faecal egg count (FEC) is a straightforward way to check if your drenching process is effective:
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Collect a faecal sample at drenching to confirm adult worms are present.
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Drench your flock using best practises.
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Collect another sample 7–14 days later to measure worm reduction.
Since you can manage the sampling yourself, there’s no reason not to perform this check at least once a year.
Getting Your Samples Tested
PGG Wrightson stores provide kits containing sample pottles. Once collected, keep samples cool in a chilly bag or fridge until delivery. Avoid leaving them warm, as this can cause eggs to hatch and affect results. Samples are then sent to a lab for analysis, and the results will be reported back to you.
By making drench checks a regular part of your farm management, you can stay ahead of resistance and ensure your flock remains healthy.
