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2021 April

Sheep lice. Source: Peter James
Sheep lice. Source: Peter James

The quiz questions are taken from:

The online learning pages focus on the important topics within worms, flies and lice and offer two approaches to learning: structured reading and question and answer.

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Answers and links to further information are provided below.

Questions

  1. Do you know the average length of the life cycle of lice?
  2. Do you know the withholding periods for fly treatments?
  3. What is the purpose of a strategic drench?
  4. Will worm resistant goats reduce the level of worm contamination on pastures?
Question 1: Do you know the average length of the life cycle of lice?

The lice life cycle takes 34 - 36 days from eggs to mature females. Eggs require specific conditions to continue to develop, and hatch after nine to ten days. Nymphs go through three stages as they moult and grow before finally reaching adulthood. Females will mate within hours of the final moulting, but won’t lay eggs for three to four days. Mated and unmated females will lay the same number of eggs, but eggs will not hatch if mating hasn’t occurred.

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Question 2: Do you know the withholding periods for fly treatments?

There are three withholding periods for meat/milk and two for wool/sheep:

  1. The Meat Withholding Period (Meat WHP) is the time from chemical application to when an animal is slaughtered for domestic use.
  2. The Milk Withholding Period (Milk WHP) is the time from chemical application to when milk can be taken from the animal for human consumption.
  3. The Wool Harvest Interval (WHI) is defined as the time from application of a chemical to when the wool can be harvested to satisfy Australian environmental requirements (also includes crutching).
  4. The Export Slaughter Interval (ESI) is the time from chemical application to when an animal is slaughtered for export.
  5. The Sheep Rehandling Interval (SRI) is the time between treatment and when wool/sheep can be safely handled without the need for protective clothing."

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Question 3: What is the purpose of a strategic drench?

It is 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 a low worm egg count at the time of this pre-emptive treatment.

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Question 4: Will worm resistant goats reduce the level of worm contamination on pastures?

Yes, A goat’s resistance to worms directly affects the number of worms it carries. In more resistant goats (those with lower WEC EBV), the worm egg count will be lower, and fewer eggs will be passed into the dung and onto the pasture.

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