Drench resistance - it’s costing you production
Released 30 Jul 2010
Dr Tessa Mills, Federated Farmers regional policy advisor
The progress of drenches for the treatment of parasites in sheep and beef has developed significantly over the last decade or so. I, along with about 200 other farmers and industry representatives, attended a meeting last month where the development of new drenches and issues such as the persistent problem of drench resistance in sheep and beef was discussed.
Drench resistance generally develops due to inappropriate, ineffective or insufficient doses of the products being administered to stock, which then favours survival of worms resistant to the drench used.
It is important to note that over the last 20-30 years there has been huge advances in the types of drenches available for use in both sheep and cattle but, at almost the same rate, resistance to these new drenches is continually developing in parasite populations.
Recent estimates suggest that resistant parasites are present in at least two-thirds of the sheep flocks within New Zealand, while all beef herds have drench-resistant parasite populations. Stock with a heavy worm burden do not thrive and productivity drops away. It is therefore critical that internal parasites are well managed on farm.
Information on how drench resistance develops and how selection for this trait in worm populations can be minimised is continually improving.
Good parasite management requires farmers to know which drenches are effective on their farms. A comprehensive drench test (faecal egg count reduction test and cultures) should be carried out regularly.
Combination drenches are likely to slow the development of a drench resistance on a property when used prior to resistance developing.
Animals should all receive optimal doses of effective drenches, body weights need to be known and your drenching gun must deliver the correct dose.
Drenching strategies will need to be tailored to suit individual farms, so seek advice.
With sensible management, the effective life of any drench combinations can be maximised on farm and the advantages of better quality stock can help farm profitability.
