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South Australia worms, flies and lice update - September 2016

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides

Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (

Spring has started brilliantly statewide with significant rains and some flooding….a stark contrast to the last 5 years for most areas. Pastures and crops have responded well as have worm burdens, so it seems.

Recent counts WormTests indicate the need for a drench in most circumstances whether lambs or ewes with the odd exception of dry ewes in lower rainfall areas. This most likely reflects a build-up of worm contamination in lambing paddocks in the lead up to weaning, and so is not surprising. The choice of drench for ewes now is not critical as most paddocks will have significant worm contamination and so the drench will be a short term “knockdown” to allow ewes a fresh start on rapidly growing spring pasture. Worm contamination will soon be diluted by the pasture mass, and ewes will soon regain condition ready for the next joining.

In contrast, a highly effective drench is desired as weaned lambs are given a fresh start on specially prepared low worm-risk pastures. Their low immune status means that a chemical boost to remove any residual worm burden will promote an optimal growth rate, and this is the objective. Soil moisture should be close to field capacity in many districts enabling an extended period of spring growth. Both the quantity and quality of this herbage mass should ensure good growth rates and limited opportunity for worms to become an issue.

The main concern post weaning is further rain that may increase the risk of diseases associated with warmth and moisture such as lameness; bacterial scours; and skin infections including flystrike. Frequent visual assessment or in the case of flystrike, preventative treatments are advised to promote good growth for sale or before pastures “hay off”.

Abundant feed doesn’t necessarily mean balanced nutrition, and a pasture test at this time of year can assess the need for dietary supplements to promote optimal health and growth. Never assume abundant pasture solves nutritional needs because there is usually a greater risk of mineral deficiencies in the better growth years.

Another useful strategy is to weigh 30–50 lambs at random and, assuming a birth weight of 4–5kg, an average growth rate can soon be calculated. Growth rates less than 150 g/day since birth indicate suboptimal performance that can affect bone strength and lifelong bone mineral status. This requires analysis to determine if there was an issue with ewe lactation or other reasons for poor lamb growth. Finding this out early is the first step to minimising the impact and preventing long term consequences. Seek advice from your animal health advisor if you have any concerns.

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