Worms present a significant production threat to grazing cattle with infection costing the industry millions of pounds a year. The main worms affecting cattle are stomach, gut worms and lungworms commonly termed roundworms (nematodes)and tapeworms (cestodes). Liver fluke (trematodes) are covered in a separate section.

The aim of any worm control strategy is to prevent the exposure of young susceptible animals to high levels of infestation on pasture in the second half of the grazing season. This can be done using:

1. Use of low risk pasture/clean grazing
2. Wormer treatments
3. Integrated systems incorporating strategies 1 and 2

However control of roundworms by clean grazing alone is impractical on many farms, due to lack of available clean grazing. Wormer [anthelmintic] treatment is often necessary.

Wormers

Wormers are vital to control worm infections and protect farmers against production losses that can cost the industry millions of pounds.

There is a vast array on the market and wormer choice depends on a number of factors: time of year, activity against different parasites, chemical class, mode of action, available handling facilities.

Due to the potential growth of resistance, the most important differentiating factor between wormers is chemical class: