Over the next two weeks, starting from March 11, the Farmers Weekly team unpacks what the drench resistance threat means for the sector, from revisiting farm systems to heeding the sheep farmers whose experience could offer a solution.
Data, not a calendar, will determine future parasite management given the depleted arsenal of animal health tools available to farmers
That’s the view of Greg Mirams, the managing director of parasite management company Techion, who has devoted 30 years to studying the issue.
He said the discovery of parasites resistant to chemical drenches is not a terminal situation for farmers but can be resolved by a reset in their approach.
“With the right information and the right support you can adjust your business and move on,” he said.
For 30 years Mirams has been advocating greater care and monitoring of the effectiveness of chemical parasite treatment in livestock, including a shift to targeted application and away from an eye assessment of animals or a calendar.
“We’ve had this ‘I’ve got a problem, I’ll shoot that problem with a drug,’ approach. Now we need to think a bit more broadly about that.”
He conducted a study that found 27% of farms have stock that are resistant to the triple combination drenches.
The implications are far reaching.
“If you buy ewe lambs and give them a quarantine drench with a triple combination drench, there is a one-third chance it will not work,” said Mirams.
By the time stock performance starts to noticeably decline, Mirams said, those animals have been compromised for up to three weeks.
“By the time you go out and see lambs are not doing well, they have been parasitised for weeks.”
The initial response is to establish the reasons for that non-performance by sampling faeces for levels of parasite eggs 10 days after drenching.
That test will determine if it is due to drug failure, incorrect dosage rates or a faulty application gun.
If it is due to parasite resistance, solutions include using rams bred with higher parasite tolerance, using novel forages that help maintain a clean environment, altering the cattle to sheep ratio, and stock rotations.
“That has to be underpinned by regular egg count data to prove that what you are doing is working.”
With 95% of parasites living on pasture, Mirams said the focus needs to be forage management that reduces larvae and lessens the reliance on drench.
Mirams saw 20 years ago that drench resistance in cattle was a looming problem given the shift to intensive calf and young stock rearing and specialist bull beef operations.
He said responses are limited because the delivery of parasite control in cattle is by pour-on or injection.
Mirams said pour-on application is linked to inaccurate and variable or sub-clinical dosages in cattle due to chemical dripping off or being licked off which can lead to developing resistance.
Solutions come back to managing larvae on the pasture.
Mirams reiterated comments from other experts that there are no new products or compounds to address the drench resistance issue due to the development and regulatory costs.
There could be some pharmacological changes to existing chemicals and possibly some “fringe developments” but Mirams said there is no certainty.
He said his message to farmers has not changed.
“It has been the same consistent message for the last 30 years but the opportunity is there. It is a management issue which requires information and support.”