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Sheep News August 2010


Every where I go I seem to see this risqué Advertisement on Bill Boards.

2 way sheep drench

No, Chemvet is not entering this market with a blue wonder pill or nasal spray for men (although Ron reckons we should at least investigate it) but it does send a message that we should all be applying to our current sheep drenches.

It is no secret that incidences of resistance by worms to the Mectin drenches is on the increase. The good news however is that Chemvet’s flag ship drench Vetmec LV is based on Abamectin which is now regarded as the ‘mectin (or ML as this group of drenches is more properly known) of choice for use in sheep and that for the vast majority of out clients Abamectin is still a very effective drench – the trick is how to keep it effective!

I recently attended the Australian and New Zealand Veterinary Associations Pan Pacific Veterinary Conference held in Brisbane. The Cattle and Sheep sections had some world class presenters and day one concentrated on worm control particularly in the face of increasing incidence of worm resistance to our current drenches. I have included some of the stand out messages and what it means to sheep farmers in this newsletter.

Kind regards, Murray Grant

STAYING Effective

One of the interesting concepts presented at the conference was that there are two goals when you use a drench. I

have since found it a very good approach to take when designing drenching programs for producers.

  • One goal is to treat the sheep and prevent gastro-intestinal worms from causing disease and production loss.
  • The other goal is to use the right drench in such a way as to minimise the development of resistance by worms to this drench.

This can be depicted graphically as follows:

Effectiveness of the strategy in treating & preventing worms
Effectiveness of the strategy in preventing resistance to the drench.

Obviously a program based on ‘Strategy C’ would not be suitable for most farmers – this strategy would be to never or very rarely drench and whilst totally minimising the onset of drench resistance won’t treat or prevent worms in your sheep.

On the other hand, a program based on ‘Strategy A’ that fully treats and prevents worms in your sheep but promotes the early onset of resistance to your effective drench is obviously not ideal either. A program fitting this strategy would be to drench every month with the same class of drench for years. The sheep would never get “wormy\”, but worm resistance to the drench would develop very quickly.

What we should be aiming at is a program based on ‘Strategy B’ that both treats and prevents worms in your sheep as well as minimising or delaying the onset of resistance for as long as possible.

Standout Messages

The standout messages to come from the presentations at the conference, with the above in mind, are as follows:

  • Abamectin is the ‘mectin of choice for sheep producers in the majority of instances.
  • Single class, long acting drench injections and capsules could be a recipe for disaster ‘resistance wise’ if used alone without other resistance fighting technique.
  • In Australia, environmental pressure on worm populations has probably a greater part to play than frequency of drenching. ie. when we drench has more bearing on the development of resistance than how often we drench. Therefore, avoid unnecessary summer drenching when the pasture is very dry. This can lead to a situation where a fair percentage of the worms that do survive will be the ones resistant to the drench. These will not be killed by the drench and will ‘over summer’ in the sheep’s gut.
  • The use of a combination drench (containing 2 -3 effective drenches that belong to different classes of drench will aid massively in the delay or prevention of drench resistance within any particular sheep flock.
  • The full time use of a combination drench is far better that rotating between the single drench classes in the combination.
  • Refugia – This is a term that we are all to see a lot more over the years to come when discussing sheep drench and worm resistance and plays an extremely important part in the resistance story. In a ‘nut shell’ it is a term that is used to describe making sure that we leave or promote a population of susceptible worm larvae (susceptible to your effective drench) in our paddocks that will act to dilute the number of resistant parasites building up in the flock.
  • The importance of other management techniques such as monitoring worm burdens using faecal egg counts (FEC), dual grazing wherever possible with cattle and quarantine drenching with a double dose combination drench.
  • Whilst a new drench is on the horizon, new ones after that are not guaranteed and may not happen in our lifetime, therefore all efforts have to be made to look after the ones that we have now.

So what does it all mean?

  • Wherever possible always use Vetmec LV and Vetmec Dual in a ‘resistance busting’ 3-way combination
  • If you haven’t done a worm drench resistance test for some time then worm test 11 days after drenching (Chemvet will supply the kits) with the combination to check that this is an effective drench.
  • Monitoring with faecal egg counts can often reduce the number of summer drenches given
  • Consider leaving some stock un-drenched particularly if going into a very dry paddock or crop after drenching
  • Whenever introducing stock onto the property always ‘quarantine drench’ with a double dose of the 3-way combination.
  • Talk to your worm control advisor before using long acting products in your pre-lambing ewes.

NEW drench on the scene…

A new class of drench was presented at the conference based on the active ingredient Monepental. The drench, Zorvix was released in New Zealand 18 months ago and will likely be released in Australia in the next 12 months. A lot of you will already have been contacted with regards this drench. Surprisingly by all accounts, the uptake in NZ has not been as high as one would have thought.

If you are going to use Zorvix or any other new drench then use it with the above strategies in mind. We recommend protecting it for years to come by:

  • Using it very sparingly
  • Always use it in combination with an effective drench such as Vetmec LV, or slightly contrary with the above, at least rotate it with Vetmec LV
  • Only use when the grass is green.
  • When using it look at leaving 5-10% of the best looking sheep un-drenched to maintain a refugia of susceptible worms within the flock.

NEW! Vetmec Allwormer for Dogs

Vetmec Dog WormerWe know this is a sheep newsletter but where there are sheep there are working dogs.

Yes our all-wormer is finally on the market. Give the dogs a treat and help fight hydatids by asking for a pack to be placed with your next drench order.

We have had great feed back so far with the most common comments being the ‘convenience of one tablet’, ‘the dogs like them’ and of course THE PRICE!!

  • Convenient farmer size pack – 10 tablets
  • Convenient dose size – 1 tablet treats most dogs (1 tab/20kg)
  • Palatable – liver flavoured
  • Effective – Treats all worms* and hydatids

*does not treat heartworm


Don’t forget…

Vetmec Mineral Mix can be used with the “resistance busting\” combination (VETMEC LV + VETMEC DUAL). Vetmec Mineral Mix which contains a number of essential trace elements for sheep and goats. Vetmex Mineral Mix contains Copper, Cobalt, Iodine and Zinc. Ask about adding Mineral Mix to your order next time you order your sheep drench with us.