This strategy describes when to use strategic drenches and how to decide when tactical/therapeutic drenches are needed.

Structured reading

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Victorian Winter Rainfall: When to test and when to drench
The times for routine worm testing and drenching in this region. Not all testing or drenching is routine; other times to do these are recommended by the Drench Decision Guide, according to details you provide about your mob of sheep.

Victorian Winter Rainfall: Drench Decision Guide
This tool recommends whether a mob should be drenched, the length of protection warranted and when to worm test again. It is your day-to-day tool on drenching decisions that should be used in conjunction with the annual program of routine testing and drenching times.

The DDG tool steers you through a series of questions about your sheep; choose the answer that applies to your mob (or make up your own scenario).

Question and answer

For those who prefer a problem based approach to learning, answer the following questions.
Each of the questions below links further down the page to the answers.

Questions:

1. What is the purpose of a strategic drench?
2. Which classes of sheep receive a routine (strategic) drench, and when?
3. Why is the second summer drench important and should it always be given?
4. The online Drench Decision Guide (DDG) for Victorian Winter Rainfall assists you to decide whether a mob of sheep should be drenched now and when to test again. Open the DDG and answer the questions it offers based on the scenario (from below) that you are using. Try at least three of the following scenarios.

• Weaners in May that received a combo drench into a prepared winter weaner paddock about a month ago, less than 5% are scouring, an egg count shows 80 epg.
• Weaners in late January that were drenched with Monepantel at weaning in early December. There are no signs of scouring and they look healthy.
• Ewes in November. No drench was required before lambing. About 15% are scouring.
• Ewes received a first summer BZ/LEV/ML drench in early December, it is now mid January. Summer has been unusually wet. Sheep are not scouring but a couple of ewes were found dead in the paddock and others are lagging during mustering.
• Late-lambing ewes in good condition just prior to being moved to their lambing paddock. A worm egg count shows 350 epg.
• Lambs just about to be weaned, they look well-grown with no obvious signs of worms.

Answers:

You can also click on each question below to go to WormBoss pages with related information.

1. What is the purpose of a strategic drench?

Strategic drench: a drench given at a critical time to sheep that are susceptible to worm infection (e.g. weaners and pre-lambing ewes) and also given at times to reduce worm larval contamination of a pasture grazed by the drenched sheep over the following weeks or months. The sheep themselves may have had a low worm egg count at the time of this pre-emptive treatment.

2. Which classes of sheep receive a routine (strategic) drench, and when?

In this region there are 2 situations where sheep should be drenched in most years, these are:

• The ‘first summer drench’ (November/December).
  All sheep mobs should be given an effective drench in most Victorian regions in November. Don't forget the rams. If in doubt about the need for a first summer drench in November, consult your vet.
• Lambs at weaning.?
  All lambs should be drenched at weaning. In spring-lambing mobs this usually coincides with the ‘first summer drench’. Weaned lambs are highly susceptible to worms and there is usually a higher worm-risk in wet seasons. Drenching will help weaners to achieve the minimum growth rates needed for survival (at least 1–2 kg/month during the summer and autumn). Use a drench shown to be effective on your property.

3. Why is the second summer drench important and should it always be given?

Note: The second summer drench (in January/February) is not routinely needed in some areas or in all years. However, it is very important because contamination with worm eggs in late summer and autumn is a strong determinant of the peak availability of worm larvae the following winter (hence worm problems will occur if it is not given); conduct a WormTest to decide whether a second summer drench is needed.

4. The online Drench Decision Guide (DDG) for Victorian Winter Rainfall assists you to decide whether a mob of sheep should be drenched now and when to test again. Open the DDG and answer the questions it offers based on the scenario (from below) that you are using. Try at least three of the following scenarios.

• Weaners in May that received a combo drench into a prepared winter weaner paddock about a month ago, less than 5% are scouring, an egg count shows 80 epg.
• Weaners in late January that were drenched with Monepantel at weaning in early December. There are no signs of scouring and they look healthy.
• Ewes in November. No drench was required before lambing. About 15% are scouring.
• Ewes received a first summer BZ/LEV/ML drench in early December, it is now mid January. Summer has been unusually wet. Sheep are not scouring but a couple of ewes were found dead in the paddock and others are lagging during mustering.
• Late-lambing ewes in good condition just prior to being moved to their lambing paddock. A worm egg count shows 350 epg.
• Lambs just about to be weaned, they look well-grown with no obvious signs of worms.