It’s that time of year in most areas of Australia to do the first strategic summer drench. A strategic drench is a ‘drench given at a critical time to reduce worm larval contamination of a pasture for the benefit of the whole mob or herd rather than just for the treated animals, and/or a drench given to sheep, irrespective of worm egg count, at times when they are expected to be most susceptible to worm infection’.1
The use of a first summer drench is still recommended best practice in the winter dominant and uniform rainfall regions of Australia.1,2
The aim of summer drenching is to remove the worms in the sheep when the numbers of infective larvae on pasture are low or in decline (due to summer weather conditions). This reduces the number of infective larvae on pasture the following winter, thereby reducing the production cost of worms and number of drenches needed over this time.
The predominant worm species of these winter rainfall regions are the black scour worm (Trichostrongylus spp.) and the small brown stomach worm (Teladorsagia spp.). These typically cause problems over the autumn and winter period when favourable conditions and susceptible livestock allow for a significant buildup of infective larvae on the pasture.
Work done by the CSIRO showed that a significant portion of infective larvae responsible for winter infections are deposited on pasture during summer by adult worms present in the sheep.4 The control of these worms over summer will significantly reduce the pasture larval burdens responsible for winter outbreaks.
The timing of the first summer drench and the need for a second summer drench varies between regions based on what is most appropriate for worm control and drench resistance management. Routine worm egg count monitoring after the first summer drench should be used to determine timing of subsequent drenches. WormBoss.com.au provides a number of recommendations for various regions regarding the timing of the first drench.1
The summer drench of choice is one that:
- Has an efficacy as close to 100% as possible – any worms that survive this treatment will result in pasture contamination. A combination of highly effective actives, such as TRIGUARD®, is recommended best practice.2,3
- Has a short duration of activity – that will apply less selection pressure for resistance at a time when there is less refugia (the proportion of worms not exposed to the drench) on the pasture to dilute contamination from resistant adults. Persistent actives such as moxidectin are recognised for their potential to select more rapidly for resistance1, and this effect can be exacerbated during times when there is less refugia on pasture.
Start your summer drenching program now to minimise the level of larval pasture contamination responsible for winter worm burdens. TRIGUARD® is an ideal choice for summer drenching due to its combination of three actives and short duration of activity.
If you require further assistance, contact your animal health advisor about the right treatment and timing in your area.