Online learning: South Australian Winter Rainfall—Deciding when to drench and what drench to use

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

Structured reading

For those who like to see all the information and simply read through it in order. Each heading is a link to a page of information—the dot point provides a summary of the page.

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South Australian 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.

South Australian 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. When is a summer drench given and to what classes of sheep?
  4. The online Drench Decision Guide (DDG) for Western Australia 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?

South-East

  • Lambs at weaning.
  • Working rams pre-joining
  • The ‘summer drench’ (Late November/December, 2–3 weeks after the feed has dried, but before Christmas)

Higher Rainfall Mediterranean

  • Lambs at weaning.

  • Working rams pre-joining
  • There are no routine drenches for breeding ewes in this zone.

Lower Rainfall Mediterranean

  • Working rams pre-joining
  • There are no other routine drenches in this zone

3. Are long-acting drenches used frequently in South Australia? 

Note: Long-acting drenches are rarely required in South Australia. Unless professionally advised, use an effective short-acting drench when treating for worms. Where treatment for barber’s pole worm is also required, broad spectrum drenches are generally effective as drench resistance in barber’s pole worm is as yet uncommon in South Australia. However, this may be changing in areas where sheep have been introduced from interstate, locations where barber’s pole worm is more common.

4. The online Drench Decision Guide (DDG) for South Australia 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.

 


Links to the learning topics for South Australian Winter Rainfall

  1. Introduction
  2. Grazing management
  3. Breeding for worm resistance
  4. Worm testing
  5. Drenching (you are currently on this page)
  6. Drench resistance management
  7. Sheep worms