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Victoria worm update - November 2013

Andrew Whale, Livestock Logic, Hamilton (

Spring just keeps on coming down in South Western Victoria at the moment.  This time last year pastures had dried off and supplementary feeding of weaners was under way. Thankfully a stark contradiction this year sees pastures still looking very lush. As always we are still able to grumble though, with many wishing the sun would come out to dry some cut hay for baling.

We have seen quite a reduction in worm egg count levels over the past month, showing how the increased levels of feed on over impact the worm life cycle. With increased levels of feed available, pasture larval levels are diluted thus reducing ingestion levels. The increased level of feed intake also plays a significant role, improving the ability of the sheep to resist worm infection.

Table 1: Livestock logic’s average worm egg counts >200 epg for all age mobs for the months from June til November.


% counts >200 epg














The reduction in worm egg count levels for November increases incentive for worm egg counts to be done in all animals, but in particular mature sheep. At Livestock Logic only 18% of mature animals have been recommended to have a first summer drench, this represents a big opportunity to not only save on drench and labour costs but to reduce selection pressure on drench chemicals. Without performing a WEC a blanket Summer drench must be performed, but based on current worm levels in mature sheep, 80% of these treatments could have been avoided.

In South West Victoria we would ideally be delaying the first Summer drench for at least another 3 weeks as current pasture and environmental conditions suit worm survival and larval pickup (not huge levels). If we can delay the first Summer drench where required and where possible it reduces likelihood of requiring a second Summer drench which is highly selective for worm resistance. We encourage producers to perform egg counts in all classes of stock prior to administering any summer treatments, and to seek advice as to what levels require treatments.

Tricia Veale, Benalla (

Very warm and dry weather is now evident in this area of North Eastern Victoria. There was 21 mm of rain for October and only 14mm so far for November.

The paddocks are rapidly drying off, many crops have been harvested but fortunately most dams are still reasonably full.

Worm egg counts appear to be at moderate to high levels as the residual underground moisture is allowing the immature worms to survive.

The purpose of the first Summer drench is to eliminate worms inside sheep as the pasture dries off. If sheep are not drenched at this time, they will continually pass worms eggs which will contaminate the pasture and become the seeds for problems later on. The timing of this drench is important. In most years, it’s usually carried out in early / mid December.

This is the time to make sure that there are no large numbers of worms inside the sheep, as most of the larvae on the pasture will be soon killed by the ultraviolet light and heat of Summer. This helps to bring about a natural break in the worm life-cycle. So check the situation by getting some worm egg counts done.

Drenching sheep unnecessarily will not only cost you money but hasten the development of drench resistance on your property. This is because you kill all the susceptible worms, so that worms that are developing resistance to certain drenches survive in greater numbers.

This is also the ideal time to get a drench resistance test done on your youngest sheep. Knowing your drench resistance status is an essential business strategy.

This test should be carried out about every 2-3 years to keep up with the resistance trends on your place.

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