Strategic drenching, quarantine drenching, exit drenching, trigger drenching, and now knock-out drenching – it seems there is no such thing as just drenching ewes or lambs anymore! The sheep industry is now awash with a number of new terms which can become quite confusing. The different drenching concepts have mostly come about as ways to slow the onset of drench resistance.

Exit drenching is the use of a 100% effective drench to kill any worms that have survived the persistent activity period of the long acting drenches or your usual lamb drench. We talk about Exit drenching around day 70-80 of 100 day drench capsules or long-acting injections, and as the last drench of your lamb drenching programme. In places that barbers pole is prevalent, it is not uncommon for lambs to receive anywhere from two -five single active moxidectin drenches (Exodus, Vetdectin, Cydectin etc.). These products are extremely useful over the late summer/autumn period, protecting lambs from the potentially lethal worm, but carry a significant risk of increasing drench resistance. Not only are they single active, but the long activity of the moxidectin molecule can allow partially resistant worms to develop and breed with other partially resistant worms. This is where the Exit drench comes in. A 100% effective drench will wipe out any of the worms that have managed to survive during the ‘tail’ of moxidectin drenches and, of the vet laboratories analysed drench testing results from 2016 showed that, of the 125 farms across New Zealand that tested moxidectin, there was resistance on 15% of farms. There are two recently developed drench actives available on the market today – derquantel and monepantel. Startect is a combination of derquantel with abamectin. Zolvix Plus contains monepantel and abamectin. Both products have demonstrated 100% kill of multiple drench resistant worms in New Zealand trials, making them excellent choices for the Exit drench. Computer modeling done by Dave Leathwick at AgResearch has shown that the use of an exit drench at the end of a routine lamb drenching programme will slow down the onset of drench resistance to the other drench classes. While the odelling has demonstrated a significant delay in the onset of resistance, it is important to remember that drench resistance is a highly complex issue. There are so many factors that contribute to the development of resistance that managing it is not as simple as just using an exit drench once a year. Come and have a chat at VetEnt this autumn about how an exit drench fits into your worm management plan.

06 April 2018, 03:06
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