Victoria worms, flies and lice update - April 2017

Hamilton: Andrew Whale, Livestock Logic (a.whale@livestocklogic.com.au)

Livestock Logic Recommendations

  • Mid May will be the time to be testing young stock for worms, that is 6 weeks post the autumn break for most south west farms
  • No doubt we are into conditions that allow for the worm lifecycle to complete
  • Weaners will require 3-weekly monitoring from here on in, and mature stock every 4–6 weeks

Over the past 5 weeks we have seen wonderful conditions in the south west for most areas. There was a widespread rain event (20–60mm) in late March that has been followed up with two more reasonable rain events and we have just also received >20mm on the 20th April. There is no arguing that this will be one of the better autumn periods experienced in the region in the past 5 years.

The critical thing for sheep producers now is getting the timing of their post autumn break worm egg count monitoring correct. Autumn break rains cause larvae to hatch from worm eggs and then develop into infective larvae that infect sheep and then develop into egg laying adults within the sheep. This process takes 3–4 weeks, so testing sheep less than 4 weeks after the autumn break will give zero indication of the post autumn break larval challenge. For this reason we recommend that weaners are tested 5­–6 weeks post-autumn break. Mature animals in good condition tend to handle worm challenge better, so we delay worm egg count testing in these until 6–8 weeks post autumn break.

For areas that received significant rain in late March this means the 10th May is the approximate date for testing weaners and late May is a good time to test mature animals. The only exception would be animals that have not been tested for >10wks and these should be promptly tested.

As with previous editions the worm risk this year will be high due to the following reasons

  • Bumper spring leaving carry over feed.
  • Much higher egg counts in all classes of stock over the past 4 months compared to the same time last year.
  • Early autumn break allows the worm lifecycle to commence therefore creating greater contamination of pastures compared to the past 4 years.