Are your sheep wormers working the way they should?
Monitoring worm burdens through faecal egg counts is a tool available to sheep farmers to save on costs and reduce labour input. Additionally, when used as part of the drench test protocol, it allows farmers to test the effectiveness of the dosing products used on their farms.
Joining Ciaran Lynch, Teagasc Sheep Specialist, on a recent episode of the OviCast podcast was Dr Orla Keane, who shared key tips and advice on monitoring parasite burden and interpreting the results.
Part of the discussion centred on the use of the drench test to test the effectiveness of dosing products, with Dr Keane explaining: “We know a lot of these drugs aren’t effective against worms on certain farms, so it is really important to know what wormers are effective on your farm.”
Providing clarity on what makes a worming product effective or not, Dr Keane said: “If the drug is effective, it should kill all of the worms and there should be no eggs remaining after treatment.”
This is where the completion of a drench test comes into play; confirming the presence of a worm burden through an initial faecal egg count, dosing the lambs, and repeating the faecal egg count one or two weeks later – depending on the product – to assess the effectiveness of the dose used.
In the case of products of the levamisole (yellow) class, the wait time between dosing and the second faecal egg count is one week, whereas it extends to two weeks for products of the benzimidazole (white) and macrocyclic lactone (clear) classes.
“When you test that second sample, if the dose has been effective, there really should be no or very close to no worm eggs remaining in the sample,” Dr Keane added.
Avoiding pitfalls
Dr Keane also noted that there are a number of factors that contribute to ensure the drench test is completed correctly, some important factors include:
- Collect the faecal samples from the same animals pre and post-treatment;
- Ensure the wait time between dosing and the second faecal test is adhered to;
- Make sure the samples are stored correctly and they get to the lab as soon as possible;
- Make sure that the lambs are dosed correctly and are dosed to the weight of the heaviest animal in the group;
- It’s best to collect the sample at the beginning of the week and send to the lab as soon as possible – avoid having samples sitting the post over the weekend;
- If samples have to be stored before posting, store them in a fridge.
In her concluding comments on the podcast, Dr Keane reiterated the benefits of completing a drench test to check the effectiveness of dosing products on sheep farms, saying: “If it helps you determine which products are effective on your farm, so that you’re treating lambs with a product that you know works and is actually killing the worms, that will pay back in spades in terms of lamb performance, in terms of slowing the development of resistance on the farm, and in terms of limiting pasture contamination for subsequent animals.”
For more insights from Dr Keane on monitoring parasite burdens and interpreting the results, listen into the full episode of the OviCast podcast below:
More information
In the below video, Michael Gottstein, Head of Sheep Knowledge Transfer at Teagasc, runs through the drench test procedure: