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Victoria worms, flies and lice update - April 2021

VIC WormBoss Worm Control Programs

VIC WormBoss Drench Decision Guides

Sheep

Goats

Sheep

Goats

Hamilton: Lexie Leonard, Livestock Logic (l.leonard@livestocklogic.com.au)

April has been relatively dry in the Hamilton region this year, and while there has recently been some rain to get grass growth started we eagerly await some more to keep the pastures ticking along. Worm burdens following the drier months have started to drop off, especially north of Hamilton. South of Hamilton we are still seeing mixed results with many mobs still returning high worm egg counts (WECs) four to six weeks post-drenching. We expect worm control to continue to be an issue over winter and into spring this year.

For winter lambing ewes, pre-lambing drenching will be high on priority lists to consider this year. Thresholds for drenching this year will likely be lower due to increased worm pasture burdens, however it is still important to WEC prior to pre-lamb drenching to ensure you are only drenching mobs that require it. Timing of pre-lambing drenching is also important to gain maximum benefit. The peri-parturient WEC rise in lambing ewes happens approximately two to three weeks prior lambing, so drenching ewes six to eight weeks prior to lambing if they already have a very low WEC is not an effective treatment. Try to drench within three weeks of the expected lambing date, but handle ewes to minimise stress.

An effective, short-acting drench is recommended pre-lambing, usually at counts >100 eggs per gram (epg) for singles and >50 epg for twins. This year, drenching thresholds may be lower depending on the worm activity on your property and pasture risk. Blanket long-acting drenching is not recommended, and if done we recommend testing at seven weeks post-drench to ensure it is working. Long-acting drenches can be effectively incorporated into season-based drench management strategies, but it is important this is done correctly so drench resistance is not promoted. A primer and tail-cut drench of a different and effective active ingredient is the most effective way to help minimise potential resistance development when using either long-acting injectables or capsule drenches.

Weaner calves should be WEC tested every four to six weeks while on pasture until spring. WEC monitoring is accurate in weaned calves and heifers until around 12–18 months of age. Is it very important young cattle have WECs done regularly and are only drenched when needed. Drench selection for cattle is also very important — oral or injectable drenches are the option of choice.

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