Colin Trengove, Sheep Health Lecturer, UA Roseworthy campus:
Winter has finally arrived in SA from mid-June ensuring sufficient moisture for the crops to go in across the State. It also heralds falling soil temperatures and reduced pasture growth. Hence the green tinge will remain just that for the next 1-2 months - in the south east in particular.
Worm egg counts (WEC) have been moderate (ie 100-300epg) through the mid north, Adelaide hills and south east, but Barber’s Pole worm has still been evident recently in the Naracoorte district with WECs > 2000 on one property. This highlights that this worm is capable of persisting into winter when circumstances suit it - despite being primarily a summer parasite. Fortunately most drench groups are still effective against this worm in SA.
Lambing is well under way in most districts but feed is generally scarce due to the dry autumn and relatively late break. This is likely to result in lambs grazing pasture sooner in life and so it is recommended that lambs have their WEC monitored from about 10 week old i.e. pre-weaning to check on worm pick-up. This is primarily to show the extent of worm infestation and highlight the importance of a weaning worm drench. An average WEC greater than 50 in 20 lambs indicates a need for a worming drench as soon as practical. It is critical to ensure lamb dungs are sampled in this instance as WECs in ewes are likely to be vastly different to lambs due to acquired immunity in ewes. This will normally require at least 20 lambs to be drafted off for sampling to ensure no confusion with ewe dungs.
Ewes and other stock should also be monitored during winter to ensure no surprises. Any sudden rise in WEC > 200 should be examined more closely to assess whether a drench is warranted. The choice of drench is not as critical at this time of year as any drench now is only seen to be a holding or 'knock-down' benefit i.e. no sustained action indicated.
Don't just assume scouring is due to worms as the short green feed at this time of year combined with lactation often reduces sheep immune status. This can result in various bacteria, viruses and parasites causing scours and needs a correct diagnosis before embarking on a drenching program. If in doubt contact your veterinary or animal health advisor to establish the best local options for dealing with worms and other health issues.