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Tasmania worms, flies and lice update - April 2018

Tasmania WormBoss Worm Control Programs

Tasmania WormBoss Drench Decision Guides





Perth: Paul Nilon, Nilon Farm Health (pandonilon@bigpond.com)

The last month has seen some rain over most sheep producing areas, save the lower east coast. While it’s not been as unseasonably hot as NSW, I don’t think there have been any frosts, so with some follow-up rain there is plenty of time for pasture growth.

Worm-wise, nothing has changed: dry sheep are good, but merino weaners are vulnerable and should be monitored religiously. Autumn/winter brassica crops are coming on line. Make sure they are protected from contamination with worms by drenching sheep onto them, to keep them low worm-risk for longer.

Now, I could discuss fluke in sheep and cattle, but that would leave nothing for next month, so please remind me. Instead, an Irish stew of observations. Why? Because all Irishmen are kings, but not all kings are Irishmen.

Here is a picture of a client’s drought-lot. He is always quick to protect pastures when things get dry. In Tasmania drought-lotting is a much better strategy than destocking. Parasitically, you would expect worms to be robust, although I do not know if anyone has studied worms in this environment. The thing to keep in mind is that there are more refugee camps than 5-star resorts, and so being worm free probably helps. Information from feedlots suggests that grain diets and fluke infections are poor co-tenants. So, I suggest drenching, including a fluke drench, into the lots. Of course, the first step is to construct and be prepared to use, the bloody thing.

While pregnancy testing a large cattle herd recently the client was weighing the cattle and drenching to weight. There are several comments about this: firstly, the splash and inhalation settled the crabs for a day or two. Secondly, if he were to truly drench to the maximum weight he would be seriously over-drenching two thirds of the mob, so it was indeed a saving. Finally, it’s good to be reminded of the weight distribution of mobs of stock. The late, great Fred Morely used a rule of thumb of 1 standard deviation being about 13-15% and about 99.7% of the animals will be within 3 standard deviations of the mean or average. These cattle were almost spot on this, with an average of 600 kg (why they were being drenched is another story) and a range of 375-800 kg. Visually, they looked homogenous. So whether we are talking sheep or cattle it pays to be mindful of weight variation. There is always the potential for under-drenching, and also toxicity [if over-drenched] at least with levamisole and the organophosphates. Many people weigh sheep before drenching, rarely so with cattle. How good are your weight estimation skills?

Editor’s note: A standard deviation is the spread of weights around the average weight. A low standard deviation means that most of the numbers are very close to the average.