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 spring lambing paddock (September/October lambing):
March and April: Prevent contamination with sheep worm eggs by spelling these paddocks, grazing with cattle or grazing with sheep for up to 21 days after the protection period1 of a drench proven effective on your property.
May, June, July and August: In some areas (e.g. tablelands), any stock including sheep can be grazed because it is consistently cold enough (mean daily maximum temperatures below 18°C) to almost stop the life cycle of the major roundworms (barber’s pole worm and black scour worm*). In warmer areas use the ’March–April’ strategy in those months where mean daily maximum temperatures are above 18°C.
Where sheep are referred to, include goats and alpacas, as they can carry sheep worms.
*Some development of black scour worms may occur until maximum temperatures fall below 15°C, but in this region barber’s pole worm control is the more important consideration.
To find out more see the following articles, located at Appendices: Further information on sheep worm control for QLD/ NSW summer rainfall/ tablelands and slopes –
- Roundworm cycle and larval survival
- Factors contributing to paddock contamination with worms
- Find you “cold period”
- Preparing lambing paddocks with “Smart Grazing” – summer rainfall
What if lambing is at another time?
Prevent contamination of the lambing paddock in the 6 months before the ewes enter the paddock. (For early autumn lambing, only 3 months preparation is required as larvae die faster in the preceding hotter months). During this 6-month period, sheep can be grazed on the lambing paddocks in months when mean daily maximum temperatures are below 18°C.
For the rest of the 6-month preparation period, the lambing paddock should be grazed by sheep for up to 21 days after the protection period1 of a drench known to be effective on your property.
To prepare a low worm-risk summer weaning paddock:
In late spring and summer, larvae on pasture die faster than in the cooler months, so preparation of weaning paddocks takes about half the time required for spring lambing paddocks.
In the 3 months prior to weaning: Prevent contamination with sheep worm eggs by spelling these paddocks, grazing with cattle (especially to stop pasture from becoming rank) or grazing with sheep up to 21 days after the protection period1 of a drench known (from a DrenchTest) to be effective on your property.
Other ways to prepare low worm-risk paddocks:
Rotational grazing with short graze periods alternated with rest periods can greatly reduce the number of worm larvae on pasture, especially barber’s pole worm. While these systems (e.g. planned grazing, cell grazing, techno-grazing and intensive rotational grazing) are outside the scope of this publication, they use the principles found in ‘Factors contributing to paddock contamination with worms’ (Appendices: Further information on sheep worm control for NSW summer rainfall/ tablelands and slopes).
1The protection period of a drench is when it is killing worms: 1–2 days for short–‐acting drenches, weeks or months for persistent products.
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