Managing Parasites of Grazing Livestock

by Bill Murphy

Abstract
Feeding livestock on well-managed pasture is more profitable than feeding in year-round confinement. Unfortunately, grazing livestock, especially animals less than 1 year old, are adversely affected by internal parasites.

We studied five grazing strategies to find ways of reducing parasitism of young stock. Two strategies kept parasite infection (except Haemonchus and Nematodirus) of young stock at low, tolerable levels.

The pasture must not have been grazed before in the same year by adult animals of the same species. If young animals are with adults (eg. lambs with ewes), the management involves grazing each pasture area only once per season. If young animals are alone (eg. dairy calves), they can graze rotationally.

Probably harsh winter conditions reduce parasite egg and larvae numbers so that low levels exist until adults shed eggs in the first spring grazing. The fresh eggs develop within a few weeks into larvae that infect young animals if they graze where adults grazed before. Farmers in northern areas can use these grazing management strategies to reduce most internal parasitism of their pastured young stock.

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