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South Australia worms, flies and lice update - August 2017

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





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

Rain has returned with a vengeance especially in the south east with many produces reporting the best season in decades. Unfortunately, this has meant too much moisture in many instances with lambs being born and raised in waterlogged paddocks. Consequences include animal health issues such as increased prevalence of arthritis.

Rainfall through the cold months of July and August has meant short green pastures for much of the state north and west of Adelaide leading to steadily increasing worm burdens. Counts have ranged from 0 to 1700 eggs per gram (epg) in both dry and lactating ewe mobs, highlighting a steady build-up of larval burdens on pastures. Feed quality is good even if quantity is lacking and so usually a “knockdown” drench at this time of year is enough to remove worm burdens long enough for sheep to return to efficient production.

Milk production is unlikely to have been hampered and so there shouldn't be a need to drench lambs before weaning. Where rainfall has been especially scarce until recently such as in the central and upper Eyre Peninsula there may be a case to check lamb worm egg counts prior to weaning as they will have started grazing and ingesting larvae earlier than most lambs.

High lamb prices have meant increased grain feeding to finish lambs. It is important to monitor worm burdens where lambs are feedlot- or confinement-fed as they are quite vulnerable to rapidly acquiring worm burdens in these situations. The other risk is introducing lambs to too much grain too quickly leading to varying degrees of acidosis. This may or may not be apparent, but can lead to set backs that encourage entertoxaemia, worm burdens and/or flystrike if conditions suit. It is always critical to slowly build lambs up to their proposed grain ration over a 3-week period to allow adequate time for the gut biome or microbial population to adjust to the change in diet.  Worm egg count monitoring and vaccination are a couple of simple risk management tools that are easily done and quite cost effective to avert these potential increased costs of production. Another is to include buffers or mineral supplements with grain feeding to reduce the risk of acidosis.

The final point is always to consider the opportunity to do a drench trial in the lead up to weaning. The better years are usually the best to check which drenches are effective. This can be simply done by checking egg counts before and after drenching with one or more chemicals, but check with your sheep health advisor if you have queries.

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