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Examine your parasite control now


By Conor Dobson,

Drystock Advior

Teagasc Longford


This time of year is often critical for parasite control while animals are at grass. The current damp humid weather is ideal for high parasite burdens and the animals most affected by parasites will be calves in their first grazing season. Other categories of stock can also be affected too though. A good mid-season control strategy will ensure that animals will perform to their optimum and will also make parasite control easier at housing. There will be a certain amount of parasites on all farms. The main parasites to control at this time of year are stomach and intestinal worms (gut worms), lung worms.

Observe animals

While animals are being checked every day they should be observed for clinical signs of parasites. These will mainly be ill-thrift, loose dung for gut worms and the distinct short sharp cough for lungworms. In more advanced cases of lungworm infection heavy breathing and panting may become evident.

Faecal Egg Counts

Faecal egg counts are very useful at this time of year to develop dosing strategies. Dung from 10-15 calves should be sampled, 8 weeks after turnout, to give a representation of the parasites present and also the level of infection. The results of faecal egg counts should be discussed with your vet and this information can be useful to select an appropriate dose.

Clean grazing

Silage after grass or new reseeds are also useful for parasite control during the summer. These will have less of a parasite burden and the better quality grass will improve the nutritional status of the animals. Well-fed animals will have a better tolerance for these parasites. We used to think that animals should be dosed and moved to the “clean” pasture but this may increase the risk of resistance of the parasites to the dose. Now it is recommended to dose the animals and move them to the “clean” pasture 48 hours after.

Product selection

There are a wide range of products for dosing and product selection will be determined by many factors such as the type of stock being dosed and whether the preference is for an oral drench, pour-on or injection. Previous history of the farm in term of parasites and parasite control is also important. For instance a farm with a history of high levels of fluke may benefit from dosing for fluke now and there are products available for such a purpose. There are a few long acting products that give season long control of certain parasites which can be useful particularly if stock are going to an out farm. It is important to accurately weigh animals so that under or over dosing is avoided.


Control of worms is usually through administration of anthelmintics of which there tends to be 3 main groups



Common Name

Admin Route


White Drenches




Oral, Inject, Pour on

Macrocyclic lactones


Inject, Pour on


The ease of administration and reduced cost of these products has led to their widespread use within the industry. This has led to the development of anthelmintic resistant worms to each of the drug classes.

Such results mean that we will need to implement a more targeted sustainable approach to gut worm control slowing down any further anthelmintic resistance.

Worm control tips:

  • Know what anthelmintics work on your farm- Rotate anthelminthic classes
  • Use anthelmintics only when needed- Use faecal egg counts to monitor worm burden
  • Use the recommended dose rate, give correctly- Do not under dose
  • Use pasture management to limit exposure of naive calves to worms where possible
  • Be conscious of biosecurity when buying animals



Teagasc provides a Local Advisory and Education service to farmers. They have offices based in Longford Town (Tel: 043 3341021), Roscommon Town  (Tel: 090 6626166) and Castlerea (Tel: 094 9620160), You can find us online at on Facebook @Teagascroscommonlongford.