Don’t get caught with worms you can’t kill
Failing to plan may result in farmers getting caught with stock suffering from parasite infections they cannot treat. That is the message from Beef+Lamb New Zealand’s Wormwise programme as farmers look ahead to the management of lambs and calves for the summer and beyond.
“Don’t get caught with worms you can’t kill,” said Wormwise programme manager Ginny Dodunski.
She said supply of the so-called “novel” drenches, Zolvix and Startect, is likely to remain constrained this season.
“Last autumn, I received calls from vets and farmers with sick lambs suffering from triple-drench-resistant parasites, and nothing to treat them with. By the time these farmers realised they had worms that could survive a triple drench, the lambs were actually very sick. Even once you treat them with a different drench family, they take a long time to turn around.”
There are also dairy support blocks and dairy beef rearing properties where tripledrench-resistant worms have developed.
Zolvix contains the active ingedient monepantel, and Startect contains derquantel. Both have been available for about 12 years, but have generally been reserved for special treatments such as quarantine drenching, knockout drenching and on farms where combination resistance has already been diagnosed. Both products are registered for sheep. Only Zolvix can be used in cattle.
On the average farm, these products should be highly effective at removing resistant parasites.
However, the manufacturers of both products advise that due to manufacturing issues, they are unlikely to be able to meet market demand this autumn. Both are constrained by the manufacturing plants that make their active ingredient.
“A farmer who has not been doing any monitoring and suddenly finds they have sick and dying lambs with combinationresistant worms in autumn 2024 may find that there is nothing available to treat those lambs with,” Dodunski said.
The best thing farmers can do is to check the performance of their drenches now.
“Collect 10 fresh faecal samples from lambs or calves after drenching — 7 to 10 days later for lambs and 14 days for calves. Options for testing are your local vet clinic or FecPak, and there are some private providers out there too ...
“If your drench is working well, there should be no eggs present after drenching. If eggs are still present, it’s time to start some conversations about where to from here. It’s not just about what product to use next time — how many young stock should you be trying to finish? What’s the best feeding and management for those — are there ways of allocating feed or organising rotations that reduce the worm challenge? Are ewes or other breeding stock as well set up as they could be, and would it be a better use of feed to get them sorted before it gets dry?”
Wormwise is a pan-industry collaborative effort, funded and run by Beef + Lamb New Zealand with input from the NZVA, APHANZ, DairyNZ and MPI to give farmers tools and skills to fight parasite resistance on their property.