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South Australia worms, flies and lice update - February 2015

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides


Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (trengovet@icloud.com)

February has been the customary warm/hot summer that we expect, but followed the mildest January in 10 years as well as an unexpected 50–100 mm rain. Recent WECs reflect this with one in three mobs indicating a need for a drench. This is higher than anticipated at this time of year and no doubt due in part to the unseasonal rain in early January. Recent reports of stock losses in the lower south-east due to Haemonchosis (Barbers pole worm) have also stemmed from this rain episode.

The need to do follow up monitoring in February has been even more critical this year and so it is hoped that stockowners will make use of this strategy to check and, if necessary, minimise the worm burdens going into winter. The crop regrowth and grass germination in January will have provided a welcome respite, but the recent burst of hot weather will have dried that off in all but the 600+ mm rainfall areas. This will have enabled worm populations to multiply in most parts of the State and monitoring is the only sure way to determine if this circumstance has created a need for a strategic summer drench. It is prudent to wait at least 3–4 weeks after significant rain to check worm egg counts, as there is a time lag between infective worm larvae on pasture being consumed and developing into egg laying adult worms.

Another consequence of unseasonal rain is the loss of water-soluble carbohydrates (sugars) from standing dry feed. The energy value of dry feed can be reduced by 10–20% with significant rain events (greater than 30 mm) and recent feed testing has revealed ungrazed cereal stubbles of exceptionally poor quality. Worm burdens are significantly influenced by livestock nutrition as the immune system and ability to maintain good health is reliant on balanced quality feed in adequate amounts. This is another reason to monitor both WEC and feed quality. Monitoring feed quantity alone is not enough under these circumstances.