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Victoria worm update - February 2014

Andrew Whale, Livestock Logic, Hamilton ( )

Summer has now come and gone for another year, and as I write this it definitely feels that way in the south west with the last few days having temperature highs of only 20 degrees and lows of 8 degrees, with about 20mm of rain in and around the Hamilton region. The seven day forecast for the remainder of Feb suggests similar conditions although daytime max temps in the high 20’s. This means that eggs that are defecated by sheep from here on in are going to survive with the help of large amounts of feed on offer in pastures following our good spring. Any rain and dew will aid these eggs to survive through to the infective larvae stage, when ingestion by sheep allows the life cycle to continue causing worms pastures to become heavily contaminated.

In short what this means for our sheep producers. You must be proactive in monitoring sheep now and have lower drench trigger levels than this time last year when we were aiming to discourage drenching when not needed as it was highly selective for drench resistance. Your autumn and winter drench problems that you experience this year will come back to how you managed worms in sheep in February, March and April. Your second summer drenching egg counts should be performed ASAP to allow for sound worm management decisions to be made. This year is a high risk year for heavy worm burdens throughout winter and action must be taken now to avoid large production losses and high animal health expenses.

The following table reflects the amount of sheep that we have recommended second summer drenching for at Livestock Logic in February to date. Note some of these sheep would not have received a first summer drench.

Class of Sheep

% Requiring Drenching

MA 2011 Drop


Maidens/Hogg 2012 Drop


Weaners 2013 drop



Not surprisingly the 2012 hoggets have a higher drench requirement than the older classes of stock. The reason for the lower percentage of lambs getting drenched would be that many of these lambs would have been drenched 5-6 weeks earlier, whereas most mature sheep do not get a follow up worm egg count until at least 2 months post drenching in summer.

We encourage all sheep producers to make use of objective worm egg counts promptly with advice from their sheep advisors to make informed decisions on their summer/autumn worm management.

Tricia Veale, Benalla (

Very hot conditions, dry brown grass, little rain and then suddenly some downpours, plus high winds have caused North Eastern Victoria to become very fire prone. In this area there was 49.5mm of rain in January and 17 mm so far for February.

Large fires have broken out in hilly country with many thousands of hectares and many animals destroyed. The support of the CFA and those who have given help to the effected farmers is wonderful. Many local people are assisting with re-fencing and providing fodder. The water levels in the dams are also now rapidly falling.

Some worms however are surviving because of being sheltered close to the ground. It's very important to test animals to determine the worm burden.

Now is the usual time for the second summer drench but it is very important not to give this drench unless it is really necessary. Drenching when it's not needed will help the worms to get used to that chemical, which allows drench resistance to begin. This is because you kill all the susceptible worms in the population… allowing the drench resistant ones to survive.

So if in doubt I suggest that you get a worm egg count done. You may wish to test a group of younger sheep and some older ones to obtain a comprehensive picture of the worm status of your property.

Also, make sure that you have a plan of your drenching regime which makes the efficient drenches last as long as possible on your property.

It is a serious mistake to use one type of drench only every year for a few years. This actively encourages the appearance of resistant worms.

If Barber’s Pole worms, Haemonchus, are present on your property, then I suggest that you keep an eye out for these blood suckers. Get a larval culture done to identify the species of worms present.

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