Drench checking is a faecal egg count (FEC) performed after drenching to confirm that a drench has worked. As the average lifecycle of strongly worms is around 21days, we normally perform a drench check, for short acting drenches at day 10 post drenching.
As the sheep will have taken in infective larvae at this stage, but these larvae will not have had time to mature, breed and lay eggs, the FEC should be zero. Any eggs found at this stage have been produced by worms not killed off by the drench or that are resistant to the drench.
To ensure that all the drenches you are using actually work on your farm, you should perform a drench check for every drench you use, at least once a year.
This is a good time of year to perform these tests as worm challenge is high and there are still young animals around to make the tests valid. Use lambs or R1 calves for best results. Long acting drenches for Barber’s Pole are not long acting for all worms so the tests are still relevant, but confirming long action efficacy for Barber’s Pole will require repeat sampling and larval cultures.
Collect a pooled sample – about 15 samples of the same size to fill the pottle. Samples can be collected from the paddock as long as they are fresh. Get the samples to us as soon as possible and you should receive the results the next day.
For further information please talk to your Anexa Vet, we’re here to help.