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South Australia worms, flies and lice update - June 2017

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





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

Unfortunately, the quarterly forecast has proven correct and we have experienced exceptionally low rainfall in June. Livestock were in good condition through autumn due to the exceptional rainfall over summer, and conditions have been mild for lambing. Consequently, modest to low worm burdens and reports of above average lamb marking percentages (%) are not surprising. Mastitis has also been a significant issue most likely due to above average milk production following these exceptional seasonal conditions.

However, short feed due to a dry start to winter will be causing close grazing and an associated increased worm pickup. There will be plenty of worm larvae on offer due to the moisture over summer/autumn and recent frosts will not have had much effect on them.

The good ewe condition will have helped to combat worm burdens to date, but lactation will be compromised by the short feed. This can lead to lambs relying more on pasture than milk in their early development and so at risk to developing worm burdens earlier than expected. Checking ewe condition and egg counts during lamb marking will assist in planning management strategies thereafter. Similarly for those still to lamb, a pre-lambing worm egg count (WEC) or drench is advised where body condition and/or short feed is a real concern. This is ideally done 4-6 weeks prior to lambing coinciding with the vaccination booster.

Another management reminder for those contemplating grazing crops due to the feed shortage is to ensure calcium/magnesium supplements are provided to prevent milk fever and grass tetany in late pregnant or lactating ewes. A vitamin ADE can also be an advantage to boost ewe calcium uptake. This is also advised for early weaned lambs given access to crops to promote good bone development.

In lean winters above average worm burdens in lambs at weaning can be anticipated and so it is a good time to plan a drench trial to see which drenches are currently effective. A WEC on lambs before weaning needs to be in excess of 250 worm eggs per gram (epg) to provide a reliable result for drench resistance testing. Discuss with your sheep health advisor if uncertain how to go about this important worm management strategy.

For June 2017 state outlooks, please follow the links below:
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