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What is Anthelmintic resistance
The genes responsible for anthelmintic resistance are believed to be present in all worm populations but at very low levels. When animals are treated with an anthelmintic, this kills all the susceptible worms allowing only the resistant worms to survive.
The surviving resistant worms output eggs with the dung onto pasture which results in resistant worms making up a much greater proportion of the worm population in subsequent generations.
How prevalent is Anthelmintic resistance
A 2017 Teagasc survey found:
How to avoid resistance
AT this stage there is evidence of resistance to all classes. All products within the same class have a similar mode of actions. So, if a parasite has resistance against a class, it will be resistant against all products within that class.
When switch products we need to switch to a different class of anthelmintic not just switch between products within the same class. Focus on the class of the products not the product name.
What are we trying to control within our winter dosing program?
Lungworm & Stomach worms
Mature cattle can build an immunity to worms. Our main concern is weanlings and animal heading for their 2nd winter. Mature animals should be dose if there’s an indication of a problem.
There are 3 families of drugs but only two families of drugs that give a full cover across the winter
Adult cattle do not have immunity. The presence of Liver Fluke depresses Liver function. This will result in reduced production, poor immunity and reduced efficacy of vaccinations.
No immunity developed. Fill a shed at the one time. Injectable iver- MECTINS only kill sucking lice. Pour-ons kill both.
Weanling Treatments this winter:
Store/Finishing cattle Treatments this winter:
Over winter dose for worms, fluke and lice. Be conscious of meat withdrawals, it ranges from 60 to 143 days with differing products. If feeding reasonable levels of concentrates, the liver needs to be in good health. Don’t delay fluke dose to long.
Dairy cows treatment across this winter:
If you dosed your cows this summer with Eprinex, use a different family like and albendazole this winter. Eprinex (wormer, eprinomectin) is a macrocytic lactone like iver – MECTIN.
As it’s the only wormer with zero milk withdrawal we should be preserving its use for summer dosing. Dectomac, noromectin and mastermectin etc are also macrocytic lactones.
Our winter worm dosing strategy should therefore be built around albendazoles like albex, albex gold
Albendazoles kill worms and mature fluke. If using an albendazoles wait 3 weeks after housing to allow maturity of all the worms. After 3 weeks housing the albendazoles will not kill immature fluke.
Therefore a 2nd dose will be needed later in the winter. The 2nd dose can be a repeat of albendazole or Rumenil to kill rumen fluke, if required. If using Rumenil as 2nd dose do not use within 2/3 weeks of calving.
If using Rumenil as 1st dose avoid using at drying off.