Anthelmintic treatment of ewes pre-lamb

The challenge of anthelmintic use in sheep continues, with both product supply and the ever-increasing evidence of anthelmintic resistance and resultant production losses.

Boehringer Ingelheim (BI) has withdrawn Bionic Plus® from the market while work is undertaken examining the pay-out of the two actives (albendazole and abamectin) in their capsule and Agritrade has given notice that it expects Centramax to be limited in supply this season.

Whether the Bionic Plus® capsule returns to the market is not yet clear. This will leave farmers searching for advice and considering the use of alternative long-acting products in ewes and hoggets pre-lamb.


Firstly, if you have identified anthelmintic resistance as an issue for your farm, and you have a control plan, please continue with this plan.

An alternative product to Bionic Plus® and Centramax is Marathon LA injection. In common with capsules, Marathon LA and the other long-acting injections, have an extended period of activity and it is this “tail” which selects for drench resistance.

Marathon LA contains the single active moxidectin (capsules have two actives), and moxidectin is one of the most potent actives for killing intestinal worms. In the injectable formulation, moxidectin will remain active against Barbers pole worm for 90+ days, black scour worms (Trichostongylus) for 42 days and Ostertagia for 100+ days.

If injectable products are to be used, implement refugia to reduce the selection for drench resistance and carefully consider the class of stock to treat.

Ideally, restrict treatment to ewes with low body condition scores, those carrying multiple lambs, mobs that are going into a feed shortage pre-lamb and younger stock, hoggets or two-tooths.

Refugia is leaving a portion of the mob untreated to allow a mix of worm eggs going onto the pasture i.e., the eggs going onto the pasture are not all coming from worms that survive the treatment.

What portion of a mob to leave? The answer is not clear, 25% is a guide but you will see figures from 5% to 50%. The larger the refugia the more protection there is.

For those who have been regular users of capsules, either Bionic Plus® or Centramax, the other consideration is that these provide treated animals with a top up of selenium and cobalt.
For those farming in cobalt deficient areas, consider the use of SMARTSHOT®. Ewes treated pre-mating with SMARTSHOT® B12 Plus SE, will provide 180 days of adequate concentrations of these essential elements. If selenium is not an issue on your farm, SMARTSHOT® is also available with just the B12 component.

SMARTSHOT® B12 Plus SE ensures adequate levels of these trace elements will be maintained in their lambs until one month of age for Vitamin B12, and from birth to weaning for selenium.

If you are farming outside of cobalt deficient areas, the use of Selovin-5™ or Selovin™ LA or use a selenised clostridial vaccine (Nilvax®, Multine® or Ultravac®) pre-lamb.
If you are unsure of the selenium or cobalt status of your flock, blood testing will clarify this.

Lots to consider in all of this; please talk with our vets or our commercial managers if you need additional advice.