Imagine a farm with lots of worms and no drench to kill any of them. would that mean you couldn’t farm sheep?
TRIPLE DRENCH RESISTANCE IS HERE NOW.
While long acting anthelmintics have a role in the management of parasites in lambing ewes and the subsequent levels of pasture contamination, their use contributes to the onset and extent of anthelmintic resistance.
With growing concern over the number of farms in NZ now showing clinical and subclinical issues with anthelmintic resistance, the following should be considered a guideline on farms where the use of long acting anthelmintics is ongoing.
Don’t overdo it, please!
This is a serious comment. Long acting drenches are used too much and without regard for refugia.
Only treat ewes that need the product.
Not all ewes and not all mobs need treating. Some farmers happily farm sheep without using long acting capsules or injections. If possible, don’t treat the whole flock. Twiners and triplets are more likely to get a benefit from injections, while singles are the mob most likely to handle being undrenched.
Provide refugia.
This is partly covered in the point above and it may need you to do something completely different from the past. For example, you can run untreated ewes (the fat ones or some singles) in mobs that have been capsuled or injected. Or make sure that mobs of untreated ewes (singles, the fat twins) graze in behind mobs of treated ewes once docking is done and the mobs are on the move. You need to get worms that have not seen a drench to breed up with the resistant bastards that will be hanging around in the lambing paddocks.
If using injections: Eweguard, Marathon LAI
Injections have a long “tail”. This means a dwindling amount of anthelmintic over time so worms get a look at a dose that may not kill them. That can make the next generation tougher to kill. As a single active product there is more risk of resistant worms escaping the kill and in some of our worst cases of multiple resistance, this drench family has been overused, especially in ewes.
Do a Primer Drench, like you do with capsules. Get rid of the resident worms in advance. In reality this is rarely done. The best drench to use will be a double combination containing a white drench and a clear drench e.g. Corporal
Do a Drench Check at 30 days. Note this is sooner than you do a Drench Check for capsules and it is timed to see what worms are present at a time when the longer acting products should still be working. We have done a lot of monitoring of injections in the last 2-3 years and there are often an awful lot of breeding worms about by then. Got refugia ewes in the mob? Mark them at set stocking and make sure there are none in the corner when you muster them up for sampling. Or run a small handy paddock with all the ewes in there treated.
Do an Exit Drench. Pretty much compulsory. We’d bet that your injection will have issues with “leakage” and that you have plenty of resistant worms in your ewes when you do a Drench Check. They will need wiping out so a combination product at docking will hopefully do that (but should be monitored too).
In reality, all the ideas above must be considered if you want to use long acting drench products. Knowing what works, knowing how well this season’s product worked and doing everything possible to reduce the risk of developing resistance are all the best ways to ensure drenches keep working on your farm.
Our recommendations will often change depending on the individual farm situation. Talking things through with one of us really helps cement in place the best plan.
