For animals at grass, internal parasites are considered one of the main threats. Worms are one of the most common parasites and can be of particular concern at this time of year. If you control worms, it will allow your cattle to perform well and be free of clinical disease. However, animals are able to tolerate a certain amount of parasites. Wormers should be used sensibly to control costs and any unwanted side-effect. How much cattle can tolerate depends on a number of factors.

Young Stock – First Grazing Season

The risk with young stock depends on when they were born, and if they have been weaned or are grazing with their mothers.

Weaned calves that are grazing for the first time are at the highest risk, if the pastures have carried cattle in the last 12 months. They have no immunity and rely solely on grass for food.

Sucklers can be susceptible. But they benefit from their mothers’ milk, which provides some protection from the effects of worms.

Spring-born calves are at the lowest risk, as grass only comprises a small proportion of their intake.

Adult Cattle

If adult cattle had adequate exposure, they are generally immune to gut and lung-worms but farmers need to remain vigilant as under certain conditions diseases can occur.

Beef cows normally do not need routine treatments. Worming at housing can still be an option to reduce gut and lung worm populations with low risk.

As there is no immunity to liver fluke, cows that graze on fluke prone pastures will need treatment at least once a year.

Bulls are more susceptible than cows, so they may benefit from worming. For the best performance, treatment should be started before the breeding season.


To control parasites, it is important to monitor young stock on an on-going basis. Perform daily checks for clinical signs of disease, such as coughing, scouring, anaemia or weight loss.

Monitor Growth Rates

If you suspect parasites are present, further investigation is essential. To get an idea of how heavily your pastures are contaminated, take faecal samples and perform worm egg counting. However, these cannot indicate the impact of worms on the health and performance of your animals. If you find fluke or lung worms in faecal samples, it is a strong indicator that treatment is required.

Taking Faecal Samples

  • The sample should be fresh and less than an hour old
  • Use an air tight bag or container
  • Keep the sample cool, but not frozen
  • Deliver the sample to a lab within 48 hours
  • Lungworm samples should be delivered as soon as possible

Targeted Treatments

For the best performance, any treatment should be targeted according to the type of worms, their life cycle stages, the time of the year and treatment history.

Wormers of the three main groups differ in formulation, activity, duration and withdrawal period. Always obtain advice on the appropriate product to use. Take special care when using combination products with broad spectrum wormers. Do not use them when a specific parasite is the target for control.

Farming app, Herdwatch, has a platform where you can input a remedy purchase and treatment. It’s an easy way to record and keep track of farm medicines.

Herdwatch is an easy to use farming app that allows farmers to spend less time on paperwork. With features including Herd Management and Bord Bia Compliance, farmers can record all treatments given to animals on the app and have easy access to withdrawal periods. For more information on Herdwatch, visit

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