Farmers have been advised to know what worms they are trying to treat in their cattle, to choose the correct anthelmintic product, and ensure that application is accurate and does not contribute to anthelmintic resistance, writes Stephen Cadogan.
With cattle and dairy farmers reporting they are unsatisfied with results of worming cattle, Paul Kennedy, Dairy Technical Specialist at Interchem, confirms that increasing resistance to anthelmintic is not just a worry for sheep farmers.
He advises that results from any sampling should be used in consultation with the vet, on herd health planning and preventative medicine use.
Results from bulk milk test screening can indicate the level of infestation in the herd, and faecal sampling gives greater feedback on individual animals or small groups.
“Lung washes conducted by vets are also becoming popular to monitor lung worm burden.”
Mr Kennedy said it is important that the right dose of wormer is given correctly to ensure maximum efficacy, regardless of the product of choice.
He said a recent European Medicine Agency report highlighted that long-acting drugs and pour-ons pose a particular risk of resistance developing to anthelmintic.
This is so because pour-ons may be associated with substantial variation in drug exposure, due to grooming behaviour, dirty coats, or weather conditions.
The variation in drug exposure in turn associated with the risk of sub-optimal treatment (which aids development of resistance).
Another recommendation is targeted selective treatment with anthelmintics, ideally followed by post-treatment check-up.
“Farmers and their advisors should be prepared for possible legislation changes, if the area of resistance keeps developing,” warned Mr Kennedy.
He said it is of critical importance that the choice of wormer has no residual effect on food product. Therefore, the choice of product must suit the stage of lactation.
For example, a zero milk withhold product allows milk to enter the tank as normal.
A worm is considered to be resistant, if it can survive exposure to a standard recommended dose.
Wormer resistance is heritable, it is passed on to its offspring.
The original guidelines for worm control were drawn up nearly 30 years ago.
Since then, worm parasite infections and wormer products have changed.
And due to milder winters, worms that do not survive well in very cold climates are now being found throughout Ireland.
Infection by cooperia (the small intestinal worm) is more common in cattle during the spring and early summer, whilst infection with ostertagia (the small brown stomach worm) and dictocaulus (lungworm) is often seen during the late summer and early autumn.
Source: Irish Examiner