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Questions

1. Will worm resistant sheep reduce the level of worm contamination on pastures?

2. Can spray-ons also be used to treat struck sheep?

3. Describe two ways of applying a backline product that help to ensure it is applied evenly and in the correct position on the sheep.


Answers

1. Will worm resistant sheep reduce the level of worm contamination on pastures?

A sheep’s resistance to worms directly affects worm egg count. In more worm-resistant sheep (those with lower WEC ASBV):

a) Fewer worm larvae eaten with the pasture are able to establish in the gut and become adults. In sheep with poor immunity, 50–60% of the worm larvae are able to become adults in the gut. In sheep with good immunity, this establishment rate may be as low as 5–10%.

b) The immune response is able to reduce the number of eggs laid by established female worms.

c) The immune response develops to a stage where established adult worms are expelled from the gut of the sheep over a period of days to weeks.

This results in fewer eggs passing in the dung of more worm-resistant sheep, and the pasture will also be less contaminated than by less resistant sheep.

2. Can spray-ons also be used to treat struck sheep?

No. These products are not suitable for the treatment of struck sheep or sheep with soiled crutches. Struck sheep should be drafted off and strikes shorn and treated as recommended with a registered flystrike dressing. Daggy sheep should be lightly crutched to remove faecal material and urine stain prior to treatment.

3. Describe two ways of applying a backline product that help to ensure it is applied evenly and in the correct position on the sheep.

a) It is sometimes easier to work from the back of the race to the front and apply the product from the tail to the poll. The operator is out of sight of the sheep so they move less than if the application starts from the poll. It is critical that the treatment is applied as directed on the label. Usually, this means evenly down the centre of the back, so any movement of the sheep that results in a distorted application line may require extra product applied to cover the other side.

b) Some producers recommend setting the applicator to half the correct dose and applying two stripes to each sheep, one from the poll to the middle of the back and the other from the tail to the middle, slightly overlapping the first strip. This helps ensure that the correct dose is delivered and that there is no wastage if the applicator is not quite empty on reaching the end of the sheep. Neither is there an untreated area at the tail or the head if the applicator is emptied too early.