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Questions

  1. Are worm eggs able to wait for months and then hatch when conditions are favourable?
  2. What is the correct length to which tails should be docked, and why is this important?
  3. How often should existing sheep on a property be checked for lice?
  4. Why is it recommended to use adult cattle in alternating grazing of goats with cattle?

Answers

1. Are worm eggs able to wait for months and then hatch when conditions are favourable?

Worm eggs require both warmth and moisture to develop to larvae (above 10–18°C depending on worm species, but ideally below 35°C, and with usually more than 15 mm rain over 4–7 days of rainy or overcast weather when the evaporation rate is low). Barber's pole worm eggs will die if these conditions are not met within 10 days of them being deposited on the pasture. Scour worm eggs are able to survive a few more weeks awaiting suitable conditions for hatching.

It is important to note that while deposited eggs will fail to develop and die during the periods of unfavourable conditions sheep will continue to be infected with any larvae surviving on the paddock from when conditions were suitable for development in the weeks or months beforehand.

2. What is the correct length to which tails should be docked, and why is this important?

The recommendation is to dock the tail immediately below the third palpable joint or to the tip of the vulva in ewes. This tail length allows the sheep to lift its tail and channel urine and faeces away from the breech area. It also reduces the risk of cancers from exposure of soft tissue to the sun. Docking the tail to the correct length at lamb marking time is crucial in minimising stain around the breech and reducing flystrike risk throughout the sheep’s life.

3. How often should existing sheep on a property be checked for lice?

All mobs should be checked for lice at least twice each year.

4. Why is it recommended to use adult cattle in alternating grazing of goats with cattle?  

While most worms are only able to successfully infect either goats or cattle, not both, there are some notable exceptions. Barber’s pole worm (Haemonchus contortus) and stomach hairworm (Trichostrongylus axei) are able to successfully reproduce within goats and young cattle (i.e. pre-weaning).

Goats can also be infected by the brown stomach worm (Ostertagia ostertagi) from cattle, unlike the situation with sheep and lambs. Adult cattle are resistant to worms, hence it is preferable to use them for alternate grazing. Grazing with adult cattle represents a period of rest for the paddock from goat grazing, during which the number of infective larvae on pasture declines because larvae continue to die.