The novel sheep drench Startect® may not be an option at weaning time this summer.
The global animal health company Zoetis, which produces Startect® announced earlier this year that a shortage of this product is likely from late 2026. The supplier of the unique active ingredient Derquantel is not continuing to manufacture the compound. Zoetis is investigating options to secure Derquantel from an alternative source.
In the meantime, there will be limited supply, and this is likely to continue through next year as well. For farmers that have planned ahead to counteract this shortage and made system changes to lower drench use in general, this won’t be a problem.
Those farmers battling triple drench resistance and relying heavily on novel drenches, the shortage of Startect® could make management of resistant worms in lambs in the autumn more problematic.
Wormwise vet Mary Bowron outlines the options for farmers who rely on novel drenches.
What to do in the meantime?
There is little that a levy body like B + LNZ can do to influence business decisions of a multinational company such as Zoetis.
This could mean farmers have to manage 12 months or longer without Startect ®. Our advice is of a similar nature to that given when long-acting pre-lamb capsules were withdrawn from the New Zealand market in 2023.
Setting up your farm system to ensure ewes are in good body condition all year round, needing minimal drench, and weaning heavier lambs is a key part of reducing drench inputs on farm.
For farmers who still rely heavily on drench, this advice may sound too mundane and uninspiring, but we know there are farmers out there who have substantially reduced their drench inputs with this approach.
These farms have set up a system where lambs spend less of the year contaminating permanent pasture with worm larvae - not just drenching a bit less through the season.
The updated Wormwise Handbook (PDF, 9.45MB) contains heaps of new information about parasite management following the Wormwise FARMED principles.
However, this new resource is very clear that we can’t provide recipes for drench use. It depends on so many variables – talk to your animal health advisor to work out solutions your specific situation.
Why checking drench effectiveness matters
Having a thorough monitoring plan to understand what drenches are working and when, is key. This season checking the effectiveness of your routine drenches earlier rather than later will give you advance warning if your treatments aren’t fully effective. Start with a check of your weaning drench. If there is a problem with your first treatment, there will be even more of a problem if you continue to use an ineffective drench multiple times through the season. By the autumn you could have a significant population of resistant parasites in your environment.
For more details on checking drench performance, see - Drench resistance – who cares?
What are your options if you rely heavily on novel drenches?
The most common worm species resistant to triple drenches in New Zealand is Trichostrongylus and this is generally a problem for lambs in the autumn - you may have heard of the "Trich Spike"!
Farms that rely completely on novel drenches to control resistant Trichostrongylus may come under pressure this autumn. With no new Startect® this season and potentially a higher demand for Zolvix® you could be heading into dangerous territory where you don’t have the option of an effective drench.
Farmers in this situation will need to figure out how they can have as few lambs as possible on permanent sheep pasture through the time that Trichs are a threat.
Could you sell more lambs store earlier in the season and make the most of continuing strong schedule prices?
For those finishing lambs; having alternative forages such as summer crops or herb/legume options to improve nutrition will also enable less drench inputs. Where cropping isn’t feasible, swapping lamb grazing areas with R1 bulls or dairy heifers may be just what the doctor ordered for both species’ resistant worm challenges!
Ensure refugia is included in your grazing management. Refugia (letting some non-resistant worms stay in the mix on pasture and in animals) slows down the development of drench resistance. You could have fat undrenched ewes following behind lambs in a rotation. Or if some lighter ewes need preferential feeding, run them undrenched with your lambs and you will get refugia for the lambs and better nutrition for the ewes.
Lastly, don’t panic. Farmers adapted to the withdrawal of long-acting drench capsules by making strategic changes to their farm systems. If you’ve relied heavily on novel drenches, use this opportunity to rethink your approach and make changes. It can be done.