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Mid-season worm control for dairy-beef systems

Mid-season worm control for dairy-beef systems

As we move through the summer and stock return to paddocks they have already grazed, parasite burdens will start to develop across farms. Tommy Cox, DairyBeef 500 Advisor, offers some key advice on dosing dairy-beef animals.

Parasites can have a significant impact on animal performance, therefore it is imperative that stock are free from burdens to prevent any impact on thrive. With the majority of dairy-beef stock now outdoors the last number of months, burdens have started to develop and, to prevent any reduction in performance, it is important to monitor the burdens present.

Worms are a particular issue in dairy calf to beef systems as, due to their age profile, the majority of the animals on the farm have very little immunity to worms. Stomach and lungworm are the main offenders. 

Calves are particularly vulnerable to infection from stomach worms, and this can result in ill-thrift and reduced growth rate. After their first grazing season, cattle generally develop sufficient immunity to prevent clinical disease; however, there has being numerous cases where older animals have had high levels of worm burden. Given this, regular monitoring is required in older groups to ensure no issues arise.

Symptoms of stomach worms can include diarrhoea, decreased appetite and loss of weight. Stomach worms can cause severe damage to the stomach and small intestine, which will cause parasitic gastroenteritis. Monitoring is essential to prevent such issues from arising.

Regular dung sampling to assess faecal egg counts (FEC) is an excellent way of way of identifying a worm burden in a group. Where readings in excess 200epg (eggs per gram) are recorded, treatment is advisable.

Control of stomach worms

Control of stomach worms on dairy calf to beef farms is usually achieved by the administration of anthelmintic doses. There are currently three classes of anthelmintic licensed for the control of stomach worms in cattle; benzimidazole (white), levamisole (yellow), and macrocyclic lactone (clear). These products have been highly effective in controlling stomach worm infection in cattle. However, recent studies carried out by Teagasc showed resistance to all three classes of product. When implementing a dosing strategy, it is good practice to alternate between the different classes of drug to minimise the risk of a potential resistance build up on farm. Taking a dung sample a few weeks after treatment is also good practice to ensure the product used gave an effective treatment.


In the case of lungworm, monitoring for clinical signs- such as a husky cough or difficult breathing - is the best way to identify if there is an issue. The recent rain after the prolonged dry spell will result in high levels of infestation. With this, farmers need to be particularly vigilant in the coming days. Heavy infestations can lead to respiratory disease and so rapid treatment is advised.

As regards treatment and control, most available anthelminthic are effective against larval and adult lungworm. Levamisole and white drenches will take out what parasites are there on the day of treatment. These classes of dose, however, will have no residual affect and as a result shorter treatment intervals will be required. On the other hand, macrocyclic lactones such as ivermectins will give longer protection. 

Best practice when dosing

When administering a drench, particular attention needs to be given to dose-to-weight calculations, so animals receive a full dose. Farmers should dose based on the weight of the heaviest animal in the bunch. Where a large degree of weight variation exists, splitting the group into a heavier and lighter group and then dosing based on the heaviest in each group is advisable.

When choosing a product, it is important to read the label and instructions carefully to ensure that you know exactly what the dose can and cannot treat. Post treatment, it is best to dose and return to dirty pasture, as this will help to reduce the development of anthelmintic resistance.

Tommy Cox is an Advisor on the Teagasc DairyBeef 500 Campaign. For more information on DairyBeef 500, click here. The DairyBeef 500 Campaign will also feature prominently at the upcoming BEEF2024 open day in Teagasc Grange.


Teagasc is delighted to invite all beef farmers and stakeholders in the Irish beef industry to BEEF2024, which will be held at Teagasc, Grange, Co. Meath, Eircode: C15 PW93, on Wednesday, June 26 from 9am to 4pm.

Dr Paul Crosson, Beef Enterprise Leader; Dr Orla Keane, Research Officer; and Pearse Kelly, Head of Drystock Knowledge Transfer, provide an insight as to what to expect on the day in this short clip:

The theme of this year’s event is ‘Securing your future’. There are significant challenges in relation to farm succession, profitability, market disturbances, reducing the environmental footprint and high costs of production, however, the market for grass-fed beef as a high quality, sustainable human food protein source is strong.

The focus of BEEF2024 will be on the application of technologies that will help beef farmers increase the profitability and environmental sustainability of their family farm businesses. The roadmap to environmentally sustainable beef production as outlined in the Signpost Programme will feature.

Find out more about BEEF2024 here.