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Victoria worms, flies and lice update - August 2018

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

Livestock Logic Recommendations

  • While animal health and weight gain typically improve over the next 2–3 months, producers should be mindful that subclinical worm burdens can stop peak production from being realised.
  • Closely monitor this year’s and last year’s drop of lambs, and also light conditioned ewes.

The conditions in the south west of Victoria are very wet with Hamilton airport recording 338 mm of rain over the last 4 months. Feed levels should start to improve dramatically with warmer weather forecast for late August as we head into spring. There have been very good lamb marking results from the June and July lambers, which is a reflection of a good season with plenty of pasture for the early lambers, and relatively benign weather particularly for the June lambers.

Over August (our typical danger month for worm related mortality events) we investigated a moderate number of cases where worms were the primary cause of ill health. This fits with the way the season is progressing for worms, it is neither a low nor a very high risk year. Similarly, the season from a rainfall perspective has been very close to average, which is a good reminder that worms love rainfall and that our better rain years are typically the higher risk worm years as numbers are able to build up for a longer period on the pasture.

While worm levels are not dramatically high there is still the need for close monitoring of at-risk stock (lambs, hoggets, lactating and light conditioned animals) over the next few months. The chart below shows that in the spring, worm levels are at their highest in all classes of animals. For all animals it is important to maximise spring weight gain and condition score improvement to reduce the supplementary feeding bill over summer and autumn, and with high grain and hay prices this year it is as important as ever to ensure we capitalise on the spring period.

The chart below shows the last 2 years of increased worm challenge to sheep in the spring compared to winter.


Now is a timely reminder to consider your drench resistance status in the lead up to weaning crossbred lambs in October, and Merino lambs later in the year. You cannot possibly formulate a good drench plan without knowing the effectiveness of individual drench chemicals. Before making summer drench decisions we would encourage producers to get a drench efficacy test done.

With ram sales coming up, as well as store ewe sales in the spring, we should also have our quarantine drench program well defined. Four drench actives including at least one of the newer actives, monepantal (Zolvix®) or derquantel (Startect®), is the recommendation.