Why do sheep need to be wormed?

Ewes should only be wormed once a year at lambing time; this will reduce the number of eggs on the pasture so that there are less for lambs to pick up. Lambs have little resistance to worms in their first grazing season but this develops with time.

How often do sheep need to be wormed?

Normally sheep should be treated every three to four weeks. Keep in mind that worms may develop resistance to a drug if exposed frequently. Lower stocking rates will reduce the intensity of the deworming program. Fewer sheep result in fewer shed worm eggs within a given area, and thereby reducing parasite loads.