Parasite Watch, Sheep farming

Two Knockout Drench options, but only one dual-active

Of the two wormers suitable for use as a Knockout Drench in lambs, vet Dave Armstrong points out that the group five product STARTECT® is the only dual-active treatment.

"This contains two wormers from different chemical groups - specifically, a group three ML and group five SI - each offering a different mode of action, with similar duration, against the same worm species, working additively with each other," he explains.

"This is known as additive efficacy, which you only get from a Dual Active Wormer, and leads to a higher level of efficacy1 against worms than can be achieved by single active alone.

Knockout drench table

"Essentially, if some resistant worms survive one active ingredient, most or all of them will be killed by the other.  The use of STARTECT as a knockout drench eliminates resistant worms that may have survived previous treatments and accumulated in the lambs.

"Using STARTECT as a Knockout Drench can also help achieve higher growth rates and quicker finish2. So for optimum financial gain, this treatment is best not left too late in the grazing season."

Knockout drench sheep cycle

Knockout Drench in action near Betws-y-Coed

By the time this year's lamb crop is sold, Dewi Ellis at Cernioge Bach near Betws-y-Coed will have employed the Knockout Drench strategy three years running. When asked what is the single most important reason, he responds ‘reputation’.

Knockout drench lambs and man

A majority of his 1,150 Lleyn ewes are bred pure to produce ewe lambs for sale as flock replacements and finished males. The remaining ewes judged not good enough for producing breeding females, a team of Texel, Suffolk and Hampshire tups are used to produced finished lambs.

As a sideline, the best of these were exhibited at the Livestock 2015 event, the Texel-crosses winning 1st, 2nd and 3rd places, the Suffolks, 1st and 5th. But Mr Ellis's mainstream business is supplying other Lleyn flocks with breeding females and it is here where reputation really counts.

With this in mind, he was willing in 2014 to consider the Knockout Drench concept during its early development, to perform what is described as pre-purchase quarantine for buyers.

For Dewi Ellis, this involves at 14 days pre-sale giving an injectable 2% moxidectin treatment (CYDECTIN® 20mg/ml LA solution for injection for sheep), then the day before sale drenching with STARTECT and housing overnight ready for transport the next morning. If, at the time, fluke is considered a risk, he also gives a flukicide treatment.

Amid yo-yo prices for sheep, it is impossible to assess the gain for Mr. Ellis in hard cash, but he says that's easily outweighed by strengthening his Cernioge Bache flock's reputation as a source of high genetic merit and high health status sheep.


1. Bartram et al, 2012, The role of combination anthelmintic formulations in the sustainable control of sheep nematodes
2. Miller et al Veterinary Parasitology doi:10.1016/j.vetpar2011.11.063

STARTECT® contains derquantel and abamectin, POM V. CYDECTIN 20 MG/ML LA SOLUTION FOR INJECTION FOR SHEEP contains moxidectin POM-VPS  For further information please see the product SPC, or contact your veterinary surgeon , SQP or Zoetis UK Ltd, Walton Oaks, Dorking Road, Walton on the Hill, Tadworth, Surrey, KT20 7NS. Customer Support 0845 3008034. Always seek the advice of your medicines provider. Use medicines responsibly (