(VALUED AT $2,500)


• Steph is once again on the hunt for dairy farmers to participate in drench resistance testing!


• All testing is free (including veterinary fees, travel, drench and laboratory work) and will include all 7 market leading cattle worm drenches


• Interested? All that is required is:


• A minimum of 90 calves of similar age (i.e. all spring or autumn drop) less than 14 months of age


• Crush or good head-bail setup suitable for weighing/oral drenching


• Availability for 2 visits 10-14 days apart


• Ability to separate 2-3 groups of calves for 10-14 days (treated with a pour-on drench)


• A personalized report for your farm will be provided within 14 days of completing the testing


Please register your interest at the Maffra Veterinary Centre on 5147 1177 or e-mail This email address is being protected from spambots. You need JavaScript enabled to view it.


Drench Resistance Trial  

We have found drench resistance in dairy herds in the Macalister Irrigation District.  There is very little known about the incidence of resistance of drenches in dairy cattle in Australia.

Our dairy resident, Dr Stephanie Bullen is currently running a trial investigating drench resistance in the area.  She plans to run the trial over a 24 month period in 2013-2014.


Study Update September 2014

Resistance to worm drenches is a familiar problem in the sheep industry and is growing in importance in other livestock industries. To date there has been very little work looking at the issue on dairy farms despite adequate parasite control being one of the most fundamental animal health objectives particularly in post-weaning replacement heifers.

Between May 2013 and June 2014 drench resistance testing was conducted on 20 commercial dairy farms in the Macalister Irrigation District. Drench resistance testing was conducted free of charge as part of a Masters research project through the University of Melbourne and Maffra Veterinary Centre.

Alarmingly, all 20 properties had evidence of drench resistance to at least one drench class in one or more worm species. Resistance in the most economically important parasite species (Ostertagia spp., also known as the small brown stomach worm) was of particular concern. Of the farms which had sufficient levels of Ostertagia spp. to measure resistance (15 farms) there were very high levels of resistance to the benzimidazole or ‘white drenches’. Therefore, there is a high risk of incomplete efficacy if dairy farmers continue to use these products without prior drench resistance testing.

What is of particular interest and importance is the emerging resistance to our newest class of drench, the macrocyclic lactones or ‘mectins’. Approximately 1 in 3 farms had low to moderate levels of resistance to this drench. Given it’s importance in control of inhibited Ostertagia spp. (Summer-Autumn) it is important all dairy farmers act now to ensure these products remain effective into the future. Some simple steps include:

1) Ensuring animals are drenched accurately - apply a weight tape or weigh a sample of animals and calibrate drench guns before every use

  1.  2) Effectively rotating between drench classes and not products (e.g. Cydectin and Dectomax are in the same class) and only using the ‘mectins’ when needed (e.g. early Autumn for inhibited Ostertagia spp. control)
  2. 3)      3)Drenching animals only where there is a justifiable need:

- Address underlying nutritional issues which make youngstock more susceptible to the effects of worms

 Conducting worm egg count testing at times of low transmission (e.g. before drenching young (<4-5 month old) heifers and in summer

Finally, drench resistance testing is relatively easy to conduct on farm or through the vet centre. ‘Drench checks’ may also be used to crudely check the efficacy of current drenches post-treatment. For advice or to book in drench resistance testing feel free to contact Steph on (03) 5147 1177.

The research was gratefully supported by the University of Melbourne, Maffra Veterinary Centre, Dairy Australia, Gardiner Foundation, GippsDairy, Rural Finance, Zoetis and Steinfort AgVet.


This is a worm egg examined under a microscope.


Sale Veterinary centre

  • Address: 262 York Street, Sale
  • Telephone: (03)5144 3100
  • Fax: (03)5144 5968
  • Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Gippsland Equine Hospital

  • Address: 31 Beet Road, Maffra
  • Telephone: (03)5147 1008
  • Fax: (03)5141 1439
  • Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
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