New Zealand

Seasonal Spotlight


Three P's to remember for your flock

Anecdotal evidence from veterinarians in the field and published case reports would strongly suggest that drench resistance, particularly for triple combination drenches, is on the rise.

It is important to your bottom line to know if the drench you are using on your farm is working. A drench that is not working can cost you 10-14% of your lamb carcass value,1,2 not to mention less hoggets up to weight for mating, and the extra feed the lambs will eat while they are on the farm for longer. Doing a drench check is easy and inexpensive and something you should be doing each year to safeguard your income.

As triple drench resistance becomes more of an issue on a lot of farms the importance of the drenches containing the novel actives Derquantel (Startect®) and Monepantel (Zolvix Plus®) becomes greater, and how you should use them, depending on your farm’s resistance status.

Startect (derquantel/abamectin combination) can be used to achieve three different goals:

  1. To protect your flock from resistance. This is using Startect as a Quarantine drench to prevent the introduction of any resistant parasites with purchased stock.
  2. To prolong the life of your older drenches. This is using Startect as either an Exit or Knockout drench. An Exit drench is used after any long acting product and a Knockout drench is the replacement of one of the routine lamb drenches with another effective drench that is different from the routine drench. Both Exit and Knockout drenches are designed to remove resistant parasites that have survived the previous drenches used.
  3. To perform better using a fully effective drench. On farms where triple drench resistance already exists, Startect can be used as a routine drench for lambs. This ensures the lambs are receiving an effective drench, which kills the resistant parasites and ensures lamb growth is not compromised.

Another important step in managing drench resistance is to ensure management changes are also made on farm so that refugia is created and pasture contamination is minimised. Just changing which drench you use is not good enough. Advice on effective stock integration and pasture management is vital, irrespective of the resistance status of the farm. Your veterinarian can help you slow down the development of drench resistance on your farm by discussing the appropriate management and drench options available to you.

Click here for more information on monitoring options and other parasite management tools, or call Zoetis technical services on 0800 ZOETIS, your veterinarian, or visit

Posted by Dr Clive Bingham, BVSc. B. Phil. Veterinary Technical Adviser, Livestock.

STARTECT is a registered trademark of Zoetis. ACVM No. A10353. All other trademarks referenced are trademarks of their respective owners.