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Tasmania worms, flies and lice update - October 2016

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

At the start of the last missive I mentioned moderate, and mostly welcome rain for nearly all areas of the state. Well, the final week of September was devastatingly wet over the whole of Tasmania. Here on the South Esk we got another mid-level flood of 7m (c.f. 10m in June). October has been consistently wet with more fronts than WW2. Add in more wind than beans in the boarding house, some snow and even hail, and you get the idea.

Just as well Tasmania is fly fishing only (or at least it should be): if you were relying on worms there would be insufficient to bait a bent pin. Mind you, this assertion is made with little in the way of egg counts. Driving around shows few mobs with any substantial dag, which is just a tad unusual for this time. Shows the benefits of good nutrition.

The early weaners will be gearing up for the weaning/first summer drench. Even in these wet years when it will be green until well after Christmas, there is little value in delaying weaning (or the first strategic drench). The exception is those people who can (realistically) expect to turn off large numbers of suckers by waiting a while. If you cannot get suckers don’t delay weaning: make use of an exceptional season before all that beautiful pasture enters the reproductive phase and loses nutritive value.

As ram sales are imminent it’s timely to mention selecting for resistance and resilience. Resistance is a measure a sheep’s ability to throw off worm burdens, and is measured by recording WECs at specified times. The raw data and historic data has been combined to rank sale rams as a deviation from an historic average. Purchasers would be looking for below average (less than 100) WEC measure. However, because resistance is, at best, only moderately heritable, and because the repeatability of measurements is low, progress towards resistant sheep has been painfully slow, even for those studs that have been including these figures it in their breeding objectives for many years. The best suggestion is for clients to put pressure on their vendors to incorporate WECs into Australian Sheep Breeding Values, rather than just putting a figure the catalogue. The ASBVs take account of figures from relatives and any correlated data to provide a figure more accurate than the raw values.

Resilience is a sheep’s ability to carry worm burdens while suffering few effects. A good idea, you may think. Not really. Firstly, there is no direct measure of resilience. The ram with a positive WEC, but which grows well above the flock average may assumed to be resilient, but there may be other explanations. ASBVs for dag are sometimes used as proxies for resilience, but again there may be many explanations. ASBVs for dag are useful selecting for sheep less likely to be struck. However, it’s suggested that the resilience is not a very useful measure because high egg output invariably leads to high contamination and sooner or later you will reach a tipping point, no matter how resilient your sheep have become.

In time, genomics will provide more powerful selection tool for these poorly inherited multi-genic traits. The warning is to beware of geeks bearing gifts: the first person on the market claiming to have a super sire with extraordinary resistance/resilience information may be flying a kite. Wait until such technologies have received LambPlan or Superior Sires approval.