Worm Control Program – Victorian winter rainfall

Program summary

The WormBoss worm control program for the Victorian winter rainfall region has five components that are most effective when used in combination.

Open the complete program (PDF)

A summary of the components is below (see links or chapters in the PDF for more details).

1. Use grazing management to create low worm-­risk paddocks

• Prepare autumn and winter weaner paddocks by using ‘Smart grazing’ where possible (details on page 18 of the PDF; or also in Appendices: Further information on sheep worm control for Victorian Winter rainfall regions). Give the weaners an effective drench before they enter the ‘Smart grazed’ paddock.
• Choose the least contaminated lambing paddocks for the most susceptible lambing ewes (maidens, oldest ewes and earlier lambing ewes).
• Select weaning paddocks with lower worm-risk—these could be hay paddocks, new pastures, stubbles or paddocks grazed by mature cattle.

2. Breed and feed for worm­‐resistant sheep

• Use rams with better than average WEC and DAG ASBVs¹ (choose the more negative values).
• Maintain good nutrition and body condition score to enhance the sheep’s immunity to worms.

3. WormTest at recommended times

• Weaners, 4–6 weeks after the weaning drench (the shorter period for autumn-drop lambs or wet summers)
• During January–February for sheep showing signs of barber’s pole worm (anaemia and lethargy)—aside from known barber’s pole worm areas this can also occur in wet summers or irrigation areas.
• All mobs in late January/early February, just prior to the second summer drench. This will usually be 6–8 weeks after the first summer drench
• Weaners, 4–6 weeks after the autumn break and thereafter through winter. However, under high risk conditions (pastures highly contaminated with worms/higher rainfall areas/wetter than normal) test as soon as 2 weeks after the break.
• 4–6 weeks after any short-acting drench.
• Higher risk mobs in July/August (usually youngest and oldest). Test other mobs if high worm egg counts are found. These results will give a check on peak winter egg counts.
• Ewes pre-lambing (provided it is at least 8 weeks post-autumn break for adults and 6 weeks for maidens). This is especially important for ewe mobs that are struggling with low condition score (less than 2.5) and/or grazing pastures of less than 1200kg DM/ha (3–4 cm pasture height).
• And at other non-­‐routine times as described in the Drench Decision Guide.

4. Drench² at recommended times

• The ‘first summer drench’ in November/December.
• Lambs at weaning.
• Sheep going onto paddocks that are to be kept low worm-risk for weaners.
• Drench all introduced sheep with a combination of no less than 4 unrelated drench groups with at least one of these being the newest drench actives: monepantel (e.g. Zolvix®) or derquantel (with abamectin—e.g. Startect®)³.
• At other times, use the Drench Decision Guide and WormTest results to make drenching decisions.

5. Manage drench resistance

• Conduct DrenchTests each 2–3 years and use DrenchCheck-­Day 14 in between.
• Avoid unnecessary drenching.
• Use effective drenches and multi-active³ combinations where possible.
• In general, use short-acting treatments and restrict the use of long-acting products for specific purposes and high-risk times of the year.
• Rotate among all effective drench groups³ for each mob (and each paddock where possible).
• Calibrate your drench guns, dose to the heaviest sheep and follow label instructions.

¹ ASBVs=Australian Sheep Breeding Values.

² Drench refers to anthelmintics regardless of route of administration

³ Drench groups are the chemical family to which an ‘active’ belongs. An ‘active’ is the chemical in a drench responsible for killing worms. Some drenches contain more than one active and are called ‘multi-active’ or ‘combination’ drenches. See ‘Drench groups and actives’ at Appendices: Further information on sheep worm control for Victorian Winter rainfall regions.

This is an up-to-date, integrated regional worm control program for sheep in the Victorian winter rainfall region. It builds upon earlier programs and accumulated knowledge (including from the University of Melbourne’s Mackinnon Project), as well as new information from the Integrated Parasite Management in Sheep project, funded by Australian Wool Innovation.

The program aims to improve the profitability and welfare of your sheep through:

• fewer deaths and illness from worms
• fewer drenches, particularly long-acting drenches
• improved productivity
• prolonged life of drenches