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Queensland worms, flies and lice update - May 2016

Brisbane: Maxine Murphy, Veterinary Parasitologist (maxine@paraboss.com.au)

Preparing the lambing paddock is the next item on the sheep worm control calendar in southern Queensland.  The first requirement for a lambing paddock is that it should have good feed and adequate shelter. Secondly, it should be low-worm risk i.e. few larvae on pasture waiting to infect the new lambs.

Information that will help you to decide about the likely level of worm contamination on a pasture is the worm burden of sheep currently grazing the paddock and the paddock’s grazing and rainfall history back to the last rains. On many properties, the last rains initiated egg hatch and subsequent infections of sheep contributed to larvae accumulating on pasture.  It was thought "too dry" for worms and sheep weren’t drenched.

The good thing about barber’s pole is that once egg hatching has been initiated it cannot be delayed, and the resultant larvae quickly emerge onto pasture. If it’s cold and dry on pasture, all the better.

Some detail: At about 20°C and relative humidity of 60%, spelling a paddock for 30 days will reduce the larval population by about 55%. This reduction may seem significant, but it is unlikely to help your worm control. A reduction of over 90% is needed for an improvement in worm control to be achieved. This will generally take 5-6 months in cooler weather.

In the months leading up to lambing do any combination of these:

  • Remove all sheep and spell paddocks from sheep grazing, typically for about 3 months. Spelling over winter could take up to 5 months if soil moisture levels are good and temperatures are mostly above 18°C. 
  • Graze with cattle at high stocking rates, and use cropping and haymaking to hasten the rate of paddock decontamination
  • For those interested in pulse rotations, graze sheep at increased stocking rates for up to 18-21 days after an effective (as shown by a DrenchTest—there are no short cuts here) short-acting drench.  Note: this will require constant stock monitoring for short periods of time.

Texas: Noel O’Dempsey, Sheep Veterinary Consultant (odempseyn@gmail.com)

The weather continues dry for most people and it is getting colder, so barber’s pole should be taking a break.

Now is the time to be putting effort into low worm risk paddocks for next season.