WormBoss worm control program

Western Australia

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.

Which sheep are most susceptible to worms

Weaners and hoggets are the class of sheep most susceptible to worms, especially when they go through their second winter as hoggets. Paddocks used by young sheep in late autumn and winter should be of the highest quality pasture as the first priority, ideally they should also be of low worm-risk. Pastures grazed after the autumn break (before the ‘hogget winter’) should be the lowest worm-risk on the farm. This will give hoggets a good start, in many cases allowing them to build immunity without suffering high initial worm burdens.

On winter hogget paddocks most contamination occurs in late summer and autumn.

Lambing ewes are the next most susceptible group, as they temporarily lose some of their immunity to worms at and after lambing. As a result, they contribute to the seasonal increase in worm numbers and subsequent infection of lambs.

The following practices to prepare or choose low worm-risk paddocks are most important in the South-East and Higher Rainfall Mediterranean zones, but can also be used in the Lower Rainfall Mediterranean zone.

Preparing low worm-risk weaning and hogget paddocks

The following practices or a combination of these can create paddocks with less worm contamination and lower worm-risk:

• Rotational grazing with sheep
  Compared to set-stocking, this typically involves creating a higher stocking rate with larger mobs (at least twice the set-stocking rate) and introducing them to the paddocks when the pasture is about 7 cm high and grazing down to 3 cm high. Aim to have a non-grazing rest period of at least 2 months in winter and 3 weeks during the active pasture growth phase.
• A non-sheep use in at least the 6–8 weeks prior to use with weaners or hoggets
  • Grazing paddocks with cattle
  • Cropping
  • Haymaking
  • New pasture establishment
• Grazing with adult sheep that have a tested low worm egg count (less than 50 epg)
• Grazing with sheep only in the 30 days after they have received an effective drench (also see ‘Smart grazing’).

Choosing lower worm-risk lambing paddocks

Choose the least contaminated lambing paddocks for the most susceptible lambing ewes (maidens, oldest ewes and earlier lambing ewes). Base this on results from WormTests from these paddocks over the last 6 months.