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Questions

  1. If a pre-lambing drench is necessary, why is it given in the three week period before the start of lambing?  
  2. What are 4 requirements of a feedlotting system for goats to ensure that feed remains free from worm contamination?
  3. How do you identify early flystrikes and what is the benefit of early detection?
  4. How can you increase the probability of finding lice on sheep in an early (new) infestation?

1. If a pre-lambing drench is necessary, why is it given in the two to three week period before the start of lambing?   

When a pre-lambing drench is recommended, it is ideally given within the three weeks before the start of lambing. Giving a drench sooner than this—particularly in the higher rainfall areas—allows more time for the ewes to acquire a substantial burden of worms before lambing starts. If ewes are to be moved to a specific lambing paddock, also try to time this to within the three weeks before lambing and give the pre-lambing drench at the move.

2. What are 4 requirements of a feedlotting system for goats to ensure that feed remains free from worm contamination?

  • There must be absolutely no grazing in the feedlot area by spraying out the grass and replacing with gravel, pine-bark or similar, or leaving as compacted dirt.
  • Feeders and waterers must be designed so that there is no manure contamination of the feed by the goats’ feet or manure. Waterers must also be kept clean and in good order, without leakages onto the surrounding area. Daily trough cleaning is recommended in even the smallest feedlot to prevent coccidiosis; this is a severe risk in feedlots with poor hygiene.
  • Grass can sometimes grow around waterers that leak and these plants should be removed as they could have high numbers of worm larvae.
  • The ration must not include cut pasture that has had goats, sheep, alpacas and ideally cattle, grazing it.

3. How do you identify early flystrikes and what is the benefit of early detection?

Signs:

  • Signs of early strike are generally only noticeable on a close paddock-inspection of a mob, not just a drive-past.
  • Early strike wounds are small (up to 10 cm wide)
  • The sheep will typically be biting or scratching at the affected area—especially with breech strike, but less so with body strike—and may stamp its feet and duck its head, but will be staying with the mob, and may cease all of this behaviour when disturbed for inspection, therefor the sheep must be allowed to settle during the inspection.
  • Maggots have commenced feeding on the skin of the sheep and the affected area will appear only a little different initially—the wool may appear lighter coloured from the chewing or rubbing—but will progressively become darker with more exudate.

Benefits of early detection:

  • Only a limited amount of toxins from the feeding maggots will have entered the sheep’s system.
  • The sheep will be suffering local discomfort and be irritated, but there will be no obvious systemic effects (as occurs with advanced strike).
  • A cost will occur from the loss of fleece removed from the strike site, the chemical treatment costs, and the time to detect and treat these sheep; there may also be some depression of wool and body growth. However, advanced strikes result in farm more significant costs regarding treatment time, chemicals and the systemic effects that can cause severe illness, loss of weight, a tender fleece, or death.

4. How can you increase the probability of finding lice on sheep in an early (new) infestation?

In the early stages of a new infestation, only a few sheep in the mob will have lice. To find them you have to first select one of the infested sheep and then find the lice on that sheep.

  • Selecting the right sheep
    If 10% of sheep in the mob have lice and you select one for inspection at random there is only a one in ten chance of selecting an infested sheep. We now know that sheep can start to rub with as few as 100 lice. Therefore, selecting a rubbing sheep for inspection significantly increases the likelihood of finding lice if they are present.
  • Finding lice on this sheep
    If a sheep has 100 lice, this is equivalent to about only 1 louse seen in every 20 partings. Because lice occur in groups and are not randomly spread over the sheep, inspecting even 20 parts will only give about a 60% chance of finding lice on this animal. Inspecting more rubbing sheep will significantly improve the chance of finding them.
  • The bottom line
    Looking for sheep starting to rub greatly improves the chance of finding lice if they are present, but even if lice are causing rubbing you may have to look very carefully to find them.