Worm Control in Cattle

The sun has finally come out for a few days this spring. This has successfully dried out the ground enough to turn cattle out. While this has been a huge relief for those mucky sheds and low forage supplies, we now need to turn our heads to grazing and the management that comes with it.

Worms and fluke present a huge threat to the health of our grazing cattle and the growth of youngstock. Generally, cattle infected with worms will present with chronic ill-thrift and will have significantly reduced growth rates, but severe infection will lead to disease and death.

Traditionally, sheep farmers have relied heavily on wormers to control internal parasites, which has led to a significant resistance problem. Fortunately, there has not yet proven to be such a resistance problem for worms in cattle.

Cattle build up a natural immunity to worms throughout their lifetime. This means that cattle in their first and second grazing season are most at risk of the health and production losses associated with worms. Fluke can affect animals of any age as they do not develop a resistance.

In order to produce a worm control plan, it is important to understand the life cycle of internal parasites and when cattle on your farm are most at risk. Typically, stomach and lungworms cause disease in the summer and autumn, while fluke cause damage mainly in the autumn/winter.

Spring-born calves that are grazing with their mothers are at a low risk of worm infection as grass does not make up much of their diet in the summer/autumn months. The most susceptible are weaned calves that are grazing pastures that have been grazed by adult cattle in the last 12 months and youngstock in their second grazing season. A good indicator for parasite burden is liveweight gain. 

All cattle are at risk of fluke, so if they are grazing pastures known to carry fluke then cattle of all ages should be treated at least annually.

AHDB has produced a document (COWS: Control of Worms Sustainably) to aid producers in using wormers efficiently and minimising selection for resistance.


If you would like to discuss parasite control on your farm, don’t hesitate to get in contact with one of the vets.