VIC WormBoss Worm Control Programs
VIC WormBoss Drench Decision Guides
The south west of Victoria and much of south eastern Australia had wonderful rains in late April and early May. In the south west, two good rain events (over 25 mm) a week apart came just in time as producers were starting to anticipate a tough winter after a failed spring. Temperatures are still above normal. Resultant pasture growth rates should be above average and produce a good feed wedge coming into winter. As winter conditions start to set in, so too do production losses from intestinal worms. However, for most producers, pasture larvae levels should be minimal due to the long, dry summer, and with plenty of feed available to boost host immunity, worm issues should remain low; similar to last year.
Monitoring with egg counts is critical to ensure increases in worm numbers are identified before they cause production loss. Waiting to see visible signs of worm infections such as scouring or weak weaners before acting means that kilograms of valuable weight gain, wool strength and potential conception rates in these ewes next year, have been lost. Weaners must be monitored every 2–3 weeks from here on in. Next move attention to the older stock.
Timing of pre-lambing egg counts is important, particularly for early lambers. Egg counts for mid-June lambers and earlier will not be a great guide as they will need to be taken in late May, only 4–5 weeks post the autumn break (depending on location). This means that the egg count may still rise sharply over lambing, so be cautious with egg counts on adult sheep early after the break.
Those lambing later (July onwards) will have much more confidence in leaving sheep with a low worm egg count un-drenched. Aim for an egg count 3–4 weeks out from lambing as this gives you time to take action without risking ewe health problems such as pregnancy toxaemia and hypocalcaemia.
The chart below shows that the percentage of high (>250 epg) weaner egg counts increased in April and in May.
Graph 1: Percentage of Sheep Requiring Drenching over the last 5 months (Source: Livestock Logic Laboratory)
We would urge producers who haven’t drenched in the last 4 weeks to check the worm status of their animals. Keep a good eye on worms for the next 3 months so that stock health is good over winter and stock are productive in the spring.