WORMWISE – sheep, goats and calves
There is a LOT of worm resistance to drenches reported by the labs, which is defined as a reduction of <90%in faecal egg count after drenching. In fact resistance has already developed to one of the “new” sheep drenches recently developed.
The Wormwise website gives some great advice for reducing the risk.
Faecal egg counts are a great way of seeing if animals actually need a drench (why waste time and money?), and if a drench has done the job (7-10 days after drenching). Simply drop off some samples to our clinic – we can give you some plastic pots.
How often do you need to drench? It depends on the pasture burden, stocking density, species grazing, weather impact on worm lifecycle, drench used…
Paddocks that just graze youngstock will develop a higher worm burden.
Co-grazing different species, or rotating youngstock with adult cattle, will reduce the worm burden.
Warm, wet weather is ideal for worms and quickens their lifecycle – some species 14 days! Does this sound familiar in the Waikato?
Oral drenches tend to have no residual activity whereas pour-on and injectable generally last a month. But oral drenches seem to be more effective in youngstock.
Check the weight of some animals, the recommended dose rate, the dose actually delivered by the gun into a measuring jug, and that the product is not out of date!
Combination drenches will reduce the risk of resistance.
Levamisole (clear drench) is still the best for cooperia ……
Refugia allows the dilution of resistant worm eggs with “normal” eggs from undrenched animals, and the resistance genes generally have an energy cost which makes them less competitive. In practice, this means not drenching the best 10% of the mob, or similar strategy.
Goats do not seem to have developed much immunity to worms compared to other ruminants, so even adults often need worming over summer. We recommend increasing the dose to about 50% above what sheep are advised.