Protect Your Flock: How to Prepare for Group 4 Worming

Sheep farmers, are you ready for the upcoming season's worming? With wormer resistance on the rise, it's essential to incorporate a group 4 (orange) wormer into your worm control strategy to prevent resistance from building up. Not sure where to start? No worries! In this blog, we'll give you some helpful tips on how to prepare for group 4 worming and keep your flock healthy and productive.

Wormer resistance is becoming an increasingly significant problem on UK sheep farms. According to published data, 94% of farms have developed resistance to white wormers, 68% to yellow wormers, 51% to ivermectin, and 19% to moxidectin. It's crucial to monitor your sheep's growth rates and routinely test your flock for resistance issues. However, don't wait until there's an identified problem before starting to use a newer worm active. The best strategy is to use a group 4 wormer at two points during the season.

We recommend swapping one dose of an older group 1, 2, or 3 wormer with Zolvix™ for lambs in the mid-late grazing season. Moreover, when administering any treatment, farmers should not worm sheep and move them straight away to clean pastures. Following a quarantine dose, sheep need to be housed or yarded for 24 hours before moving them to dirty pastures. For break doses, keep lambs on dirty pasture for three to four days after treatment. These practices should help reduce the impact of surviving worms.

It's especially important to remember that not all wormers are effective against all types of worms. Skipping a group 4 dose could lead to an increase in wormer resistance and leave your flock defenseless against parasites. By incorporating group 4 worming into your management strategy, you're helping to keep your sheep healthy and productive, ensuring that you can continue to run a sustainable operation for years to come.

Still not convinced? Let’s bust some common myths about wormer resistance

Myth 1 - I don't have resistant worms on my farm

Many farmers mistakenly believe they don't have resistant worms on their farms. Studies actually show that if they were to look for them, they'd find worms resistant to one or more wormer groups on 98% of farms, and even worms resistant to two or more wormer groups on 77% of farms! It's really important to be aware of this hidden problem and take the necessary measures for effective treatment.

Myth no 2 – My wormers are working as well as they’ve always done.

According to a recent survey, a whopping 86% of farmers believed their wormers were still doing the job, judging by the look and condition of their sheep. However, here's the catch: the data shows that even without any visible signs of illness, a worm burden can slash lamb performance by up to 50%. Monitoring and tackling this invisible issue early on is absolutely crucial to avoid it turning into a major problem. So, keep an eye out and take action!

Myth no 3 – I need to save the newer wormer groups to use if the older, cheaper wormers fail.

Using the same active ingredient in wormers too often can result in worms developing resistance. Depending solely on newer products will eventually lead to their failure from overuse. By integrating newer actives into the worm control strategy, we can prolong the effectiveness of older groups and maintain effective worm control without excessive reliance on the new actives.

Myth no 4 – The newer wormers are expensive, I can’t afford to use them.

You can’t afford not to!

What to do now?

To identify resistant worms on your farm or in your lambs, you have two options: you can perform a drench check after each wormer treatment to assess any remaining worms, or you can try newer wormers like Zolvix™ as a break dose during the grazing season. Visit or for more information on sample collection and to see the difference for yourself.

Wormer resistance is a growing and invisible issue in the farming community. However, by using group 4 worming in your worm control strategy and keeping your flock on a sustainable worming programme, you can prevent wormer resistance from building up. It's essential to be proactive by incorporating a group 4 wormer into your sheep's health routine and collaborating with your vet to monitor and test for resistance issues. By doing so, you'll protect your flock's health and maintain efficient production - ensuring your business's longevity. For any further advice, give us a call or come and see us at Meirion Davies. We’re always here to help you and suggest the best way to tackle these common problems, together. 

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