Colin Trengove, Sheep Health Lecturer, UA Roseworthy campus (firstname.lastname@example.org):
The long and mostly hot dry continues in SA which is ideal for eliminating worm larval contamination on pasture. This is good for worm control leading into winter given that the worm population is largely surviving solely in the gut of livestock.
Worm egg counts (WEC) in February are the best means of assessing the potential worm risk following the Autumn break, but drenching is only indicated if counts are above 100 eggs per gram. Even in this circumstance the decision to drench will depend on the age, condition score and pregnancy status of the sheep, as well as the intended use of the paddock. For example, potential sheep worm contamination on a paddock after the Autumn break is of little consequence if the paddock is to be cropped or used for cattle grazing. If the sheep are adult, dry and in good condition, they may comfortably carry a WEC of 100 or more and not need a drench. In contrast, a drench would normally be recommended for weaners or hoggets with this worm burden.
The bottom line at this time of year is all about minimising worm contamination and the need to drench during the rest of the year. Egg count now to see what the risks are, but don't drench unless there is a particular need.