Worm burdens in animals at pasture are an inevitable fact of farming in Ireland. With calves and yearlings being turned out this Spring, farmers are planning pasture management and should also be putting a worm control plan in place for the entire grazing season. Worms can have a huge effect on both the health and performance of all cattle, in particular first-season grazers and yearlings. Whether they are dairy heifer calves, who need to be putting on at least 750g/day  to reach sufficient weight to be on target for breeding or beef calves to maximise production, they cannot afford to be pulled back by worm burdens. Worm burdens affect cattle thrive and suppress animal’s appetite which will inevitably affect their daily live weight gain.

Some farmers tend to leave dosing of animals until later in the grazing season, waiting to hear the first few coughs before taking any action with regard to worming. This approach requires quick and accurate recognition of the clinical signs and assumes prompt treatment. It ignores the subclinical element of worm burdens that reduce growth rates as well as allowing pasture contamination to build up earlier in the grazing season.

Worming animals earlier in the grazing season will help reduce the level of worms on the pasture, minimising the worm challenge throughout the grazing season and also has the benefit of dosing animals at lighter weights, thereby using less product and reducing costs.

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  • Infective worm burdens increase on pastures as the grazing season progresses. These worms will stop cattle from thriving and can cause disease and even deaths. Taking fresh dung samples and asking your local vet to do a faecal egg count is a good way of determining if animals need a dose or not. The added complication in cattle is hoose(lungworm). Unfortunately lung worm causes disease and death before they become adults and before they are detectable in dung. The best on farm test for lungworm is your own ears! If you hear cattle coughing while at grass in the summer or autumn, and if they have not been dosed recently, it is quite likely they have lungworm and need to be dosed.

    The lifecycle of the important worms of cattle is around 3 weeks so cattle can have worm infections within a month of turnout.

  • Frequency of worm dosing is dependent on which product you choose. If you use a product with no persistent effect then animals will usually require dosing every 3-4 weeks because the typical worm lifecycle takes 3 weeks.

    If using a product with a persistent effect, (macrocyclic lactones) such as ivermectins, doramectin (Dectomax) moxidectin (Cydectin) you add 3-4 weeks to the duration of the products persistency. For example Cydectin pour on provides a 5-6 weeks persistent effect and therefore can be used every 8-10 weeks for worm control.

  • The older white (benzimadazoles) and yellow (levamisole) doses have no persistent effect against worms, i.e.these wormers kill the worms the day the animals are dosed but the following day the animals could pick up new infections. The Ivermectin pour ons offer 2-3 weeks protection against re-infection. The Cydectin Range of wormers contain moxidectin and offers from 5 weeks to 17 weeks persistence, depending on the product and the specific worm. The advantage of this is that cattle treated with a Cydectin product have to be dosed less frequently and can even receive their “housing dose” up to 5 weeks before they are housed. The benefit of this is that all the worms can be removed from the animal, and the organs, in particular the lungs, can fully recover from the damage that the worms inflicted while they are still out in clean fresh air. When they are housed they will have a clean, healthy set of lungs to combat the dust and viral infections they will encounter in the shed.

  • The most significant stomach and gut worms (gastrointestinal) in cattle are Ostertagia and Cooperia.

    Lungworm, also known as Hoose pneumonia is caused by Dictyocaulus vivparus.

    These three worms are the most important worms affecting cattle health in Ireland.

    Liverfluke is also a very important parasite in livestock in Ireland and further information can be found in the liver fluke section on this website.



> Protect your cattle now 

> Use wormers in a planned and responsible manner

> Maintain effectiveness of wormers in the future

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