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Dose and Return - Why?
22
May

Dose and Return - Why?

A question often asked – “do I go back to where I came from after dosing animals, or move them to fresh pasture?”

When using products with zero persistency, like Albex, Chanaverm, Zerofen or Bovex, advice is to return to the pasture from which animals came, for 4-7 days before moving on to fresh ground.

Contrary to popular belief, this has nothing to do with ‘shedding’ worms.

We do this to re-infect sheep with susceptible worms again.

Any worms left in the animal post-treatment are resistant to our dose and resistance is unfortunately a growing phenomenon.

Resistant worms mating with susceptible worms will produce susceptible offspring, diluting down resistance levels.

However, if we move onto new pastures with solely resistant worms in the sheep, there will no/potentially only a very small population of susceptible larvae present on the pasture and the resistant worms in the sheep will only have other resistant worms to breed with. Soon the worm population in this field will be completely resistant to our dose - resistance breeds resistance.

So, we return to old, dirty pastures to re infect our sheep. That way, the eggs being shed on the new pasture will include a significant portion from worms that are susceptible to our dose. This is important in slowing down the onset of wormer resistance.

Do worry about re-infecting from a production or welfare point of view, it takes weeks before ingested worm larvae might cause problems to the animal.

What about products with persistency?

A question often asked – “do I go back to where I came from after dosing animals, or move them to fresh pasture?”

When using products with zero persistency, like Albex, Chanaverm, Zerofen or Bovex, advice is to return to the pasture from which animals came, for 4-7 days before moving on to fresh ground.

Contrary to popular belief, this has nothing to do with ‘shedding’ worms.

We do this to re-infect sheep with susceptible worms again.

Any worms left in the animal post-treatment are resistant to our dose and resistance is unfortunately a growing phenomenon.

Resistant worms mating with susceptible worms will produce susceptible offspring, diluting down resistance levels.

However, if we move onto new pastures with solely resistant worms in the sheep, there will no/potentially only a very small population of susceptible larvae present on the pasture and the resistant worms in the sheep will only have other resistant worms to breed with. Soon the worm population in this field will be completely resistant to our dose - resistance breeds resistance.

So, we return to old, dirty pastures to re infect our sheep. That way, the eggs being shed on the new pasture will include a significant portion from worms that are susceptible to our dose. This is important in slowing down the onset of wormer resistance.

Do worry about re-infecting from a production or welfare point of view, it takes weeks before ingested worm larvae might cause problems to the animal.

What about products with persistency?

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