Effective grazing management reduces the exposure of sheep to worms. This involves:
Weaners are the class of sheep most susceptible to worms, especially when they go through their first winter. Paddocks used by weaners 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 (the weaners’ first winter) should be the lowest worm-risk on the farm. This will give weaners a good start, in many cases allowing them to build immunity without suffering high initial worm burdens.
On winter weaner paddocks, contamination from worm eggs arises from two key periods. Most contamination occurs in late summer and autumn, however about 40% can come from worm egg deposition during late spring and early summer. Routinely giving a summer drench in November/December greatly reduces the late spring/early summer contamination.
Prepare these by the ‘Smart grazing’ method*:
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 minimise 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’.
To prepare a low worm-risk late spring or summer weaning paddock
Graze the most susceptible lambing ewes (maidens, oldest ewes and earlier lambing ewes) on the least contaminated lambing paddocks. Use WormTest results from the autumn and winter to estimate likely paddock contamination.