Knockout drenching is the substitution of one routine lamb drench with STARTECT. Resistant parasites which have survived and accumulated from the preceding drenches are then knocked out by STARTECT.
Knockout drenching has been shown to delay the onset of resistance to the existing routine drenches used.1 This works by reducing the period of reproductive advantage for resistant parasites over susceptible parasites, thereby reducing the resistance gene frequency in the population.
A Knockout drench can be given to lambs at any time – modelling demonstrates that there is a benefit in delaying anthelmintic resistance whenever the Knockout drench is given.
The greatest benefit is seen when a Knockout drench is given just as conditions become favourable for larval survival and development on pasture. The ideal timing for a Knockout drench will generally be late summer/early autumn, to prevent an autumn larval peak of resistant parasites on pasture.
A strategic drench plan could include a Knockout drench, Exit & Quarantine drenches.
1. Leathwick D 2009. Managing anthelmintic resistance: Modelling strategic use of a new anthelmintic class to slow the development of resistance to existing classes. NZVJ 57, 4, 203-207.test