WormBoss worm control program

NSW non-seasonal rainfall

Grazing management

Effective grazing management reduces the exposure of sheep to worms. There are three methods:

  • Avoid paddocks heavily contaminated with worm larvae.
  • Reduce contamination of paddocks with worm eggs.
  • Allow time for most of the eggs and larvae on the pasture to die.

The last two are used to prepare ‘low worm-risk’ paddocks for lambing ewes and weaners.

How are low worm-risk lambing and weaning paddocks prepared?

Ewes temporarily lose some of their immunity to worms at and after lambing. As a result, they contribute greatly to the seasonal increase in worm numbers and subsequent infection of lambs.

Weaners are also highly susceptible to worms. Low worm-risk weaning paddocks give weaners a good start so they can build immunity without suffering high initial infections.

To prepare a low worm-risk paddock

Whether the paddock is for lambing ewes or for weaned lambs the method of preparation is the same. However, the length of preparation will vary according to the time of the year the paddock first needs to be used. Refer to Table 1 (below) to find out how long you need to prepare your paddock.

Preparation: In the months (see Table 1 below) before it is required for use as a lambing or weaning paddock, prevent contamination of the paddock with sheep worm eggs by any combination of these:

  • spelling (including cropping and haymaking)
  • grazing with sheep  for up to 21 days after the protection period1 of a drench proven effective on your property (11–2 days after short-acting drenches, weeks or months for persistent products).
  • grazing with cattle

Table 1. Months of preparation required for low worm-risk paddocks

The first month weaning or lambing starts Cooler tablelands areas of this worm control region* Hotter western areas of this worm control region**
July, August, September or October 5 4
November or December 4 3
January, February, March or April 3 2
May or June 4 3


* includes towns such as Bathurst, Orange, Goulburn, Yass

** includes towns such as Tottenham, Condobolin, West Wyalong, Narranderra

To prepare a winter weaner paddock using ‘Smart grazing’

The paddock(s) that will be used by weaners after the autumn break should previously only be grazed by sheep that have received an effective summer drench, or adult cattle (over 12 months old). To minimize contamination with worm eggs graze only for 30 days after each drench is given. A similar stocking rate to continuous stocking will be achieved by stocking at 2½–3 times your normal stocking rate.

If there is excess feed, the summer drenches can be 'staggered' for different mobs so as to provide a longer intensive grazing period, as removing excess feed enhances the kill of worm larvae with summer heat. 

Give the weaners an effective drench before they enter the 'Smart grazed' paddock after the autumn break. *‘Smart-grazing’ is a specific effective strategy developed by the Mackinnon Project, University of Melbourne, in Victoria: see ‘Smart grazing for weaner worm control’. 

Other ways to prepare low worm-risk paddocks:

Rotational grazing with short graze periods alternated with rest (e.g. planned grazing, cell grazing, techno-grazing and intensive rotational grazing) is outside the scope of this publication. However they use the principles outlined in Factors contributing to paddock contamination with worms.