Test regularly to get the most out of wormers this season

Regular testing is key to getting the most out of wormers and maintaining their long-term effectiveness on sheep farms for years to come.

That is the message from independent sheep consultant, Nerys Wright, who emphasises that testing is vital to ascertain if, and when, a wormer treatment is required, and to then check the treatment has worked.

“No two years are the same for worms, and you don’t necessarily need to use a wormer at a specific time just because it’s what you’ve done previous years or your neighbour has done it,” explains Mrs Wright.

“Once you factor in the added complexity of climate change and hugely variable weather patterns, it’s clear that testing is the best way to find out what you need to do.”

She recommends faecal egg count (FEC) testing each management group of sheep every three to four weeks.

“In an ideal world, I’d choose a day of the week for testing and test one management group on that day every week, so each group is being tested on a rotation,” adds Mrs Wright.

“Once you have the results, it’s important to interpret them properly, so speak to your vet or RAMA for advice on analysing the results, whether a wormer is required, or if it’s best to test again in a set time.”

Similarly, Mrs Wright advocates carrying out post-treatment FEC tests to assess the effectiveness of the wormers when they are used, and to establish an understanding of wormer resistance in the flock.

“An efficacy test after every treatment will help build up a picture of any resistance far sooner than waiting to see any clinical signs of the issue,” she explains.

“This can be carried out seven days after treatment for yellow drenches, and 14 days after treatment for all other wormer groups.”

She adds: “By testing, you gain an understanding of what wormers work in your flock at different times of the year, and you can then work out the best way of using them.”

Having anthelmintic resistance is not a sign of poor farming and can be managed to maintain flock productivity.

Mrs Wright adds: “Knowing how effective the different groups are on-farm can help them be used successfully when they are most effective and prolong their useful life.”

To help slow down the rate of resistance to the group 1, 2 and 3 wormers, she advocates using the newer group 4 and 5 wormers, such as Zolvix™, for quarantine and mid to late season break doses in lambs.

“When you’re buying in sheep, you don’t know the resistance status of the flock they’ve come from, so I’d treat them with a group 4 or 5 because we know they have the highest efficacy, and they will effectively remove resistant worms in those new sheep,” she explains.

“And when you’re getting into the mid-late grazing season and there’s a high worm count in your lambs, that’s when you go in with the break dose to kill off any resistant worms and stop them being carried over to the next season.”

Mrs Wright warns against delaying the use of newer wormers until older ones fail completely, calling it a false economy.

“If we wait until groups 1, 2, and 3 are no longer effective, we’ll end up relying too heavily on groups 4 and 5, which will accelerate resistance to them,” she says.

“By using the newer wormers strategically now, we can extend the useful life of all wormer groups.”