Anthelmintic resistance 'may be common' on dairy calf to beef farms
Anne Kelleher, Barbara Good and Orla Keane of Teagasc undertook research to discover the extent of anthelmintic resistance on beef farms
Irish beef production is predominantly pasture-based, with grazing calves naturally exposed to gut worms.
Gut worm infection can cause ill-thrift and good worm control is highly dependent on effective worming products.
However, a direct and unavoidable result of the continuous use of wormers is the development of drug-resistant worms.
These are worms that can survive a dose of the wormer that would normally kill them. The main gut worm species which infect cattle in Ireland are Ostertagia and Cooperia.
Ostertagia is the main genus associated with disease, while the less pathogenic Cooperia is the main contributor to faecal egg counts.
Disease may also be more common in the second half of the grazing season due to the build-up of larvae on pasture over time.
There are currently three classes of anthelmintics available for the treatment of gut worms in cattle, benzimidazoles (white drenches), levamisoles (yellow drenches) and macrocyclic lactones (clear drenches).
Anthelmintic resistance to all three classes of drugs has recently been found on Irish sheep farms; however, the extent of resistance on cattle farms was unknown.