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Online learning: Pastoral—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.

Tip: Keep this page open and open the links in new tabs.

Pastoral: 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.

Pastoral: 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. The online Drench Decision Guide (DDG) for Pastoral 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?

Drench with a short-acting drench if:

  • This is a new mob (or rams) being introduced to the property
    Refer to ‘How can drench-resistant worms be kept out of your property?’ Sheep coming from properties with liver fluke should also be treated with triclabendazole.
  • Predicted extensive flooding is expected to isolate and restrict sheep for some weeks
    Drench (without a prior WormTest) prior to the flood arrival. Consider a long-acting product only if sheep are likely to be isolated for more than 6 weeks and they are in a summer rainfall area and ground conditions are wet. Also consider a fly preventative treatment and then move sheep to higher paddocks.
  • The mob’s WormTest result is equal to or above the threshold figures in the table below for the class of sheep and the type of WormTest result.

Table 1. Threshold worm egg counts at and above which sheep should be drenched in the Pastoral region.

Class of sheep No culture or culture has less than 60% barber’s pole
(i.e. mostly scour worms)
Culture has more than 60% barber’s pole
Ewes (dry to mid-pregnancy) or wethers 400 epg 800 epg
Ewes pre-lambing 300 epg 300 epg
Sheep under 18 months or rams 300 epg 500 epg

 

 

 

 

 

 

 

 

3. The online Drench Decision Guide (DDG) for Pastoral 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 Pastoral

  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