From weaning to maturity is a critical period while the young ruminant develops all the systems for maximum production. Worms such as Ostertagia, Cooperia and Trichostrongylus can severely limit the potential life time production capacity. The signs of worm infestation are illthrift, dirty tails, and potbellies.

The goal of parasite control is to minimise the exposure of young animals to worm larva on the pasture. Strategic or regular dosing of young stock during the summer and autumn will help reduce contamination of pastures in the autumn and early winter when survival of free living worm larvae is high. Late winter dosing will help reduce contamination of spring pastures. Larval uptake by young cattle will be reduced if they graze pastures previously grazed by other species or older cattle; or new grass or hay and silage paddocks.

Treatment of worms is based upon the three major anthelmintic groups available. They are the Benzimidazoles or white drenches; the Levamisoles or clear drenches; and the macrocyclic lactones or avermectins. The anthelmintic group used should be changed on an annual basis to help slow the development of resistance by worms to the drench group.