Do you have drench resistance on your property?


When it comes to preventative management for your cattle, do you ever ask yourself…

  • What animals should I drench?
  • When should I drench them?
  • What product should I use?

These questions are becoming increasingly important given the changing landscape of drench resistance in the Australian cattle population.


Out of all the endemic diseases in Australia, worms along with other parasites, have the largest financial impact on farm poductivity. Parasites can be grouped into either internal parasites including worms, flukes and protozoa (cryptosporidium, coccidia, giardia) or external parasites including ticks, lice and mites. The important things to consider when managing worms on farm are determining if there actually is a worm burden in the herd and then identification of the type of worm, methods to control the infection and consideration of any worm resistance to drenches.


Our  faecal egg counts!

On your own property, it is important to firstly confirm if there is in fact a current worm infection. Then we need to identify the type of worm or worms and the magnitude of the worm burden within the herd, to then determine what treatment protocol is most appropriate. The easiest way to do this is to bring in a faecal sample to the clinic, on which we can perform a faecal egg count (FEC). We can then establish if there is infection and whether drenching is required, rather than performing routine drenching, which can led to worm resistance to those drenching products. It is also likely that some properties are drenching cattle routinely when they have no worm burden at all, wasting money annually on drenching products and building drench resistance.


Over the next few months we will be running FREE FECs with help from Coopers® who are interested in determining the degree of drench resistance in cattle on the Fleurieu Peninsula. When bringing in your samples, it can be for individual animals, or a pooled sample from the cattle that you believe are looking the worst, or are most at risk and are possibly showing the classic signs including scouring, weight loss, pale gums and membranes around the eyes or bottle jaw (depending on the worm type).

Identification of worms

A FEC is the easiest way for us to determine the type and number of worms on your property. On the Fleurieu Peninsula, the worm species of importance include Cooperia (see picture below), Ostertagia, Trichostrongylus (black scour worm) and Haemonchus (barbers pole worm). There are several predisposing factors that will contribute to the worm burden on you property. These factors include high rainfall (500-600mm annually or irrigation), high stocking rates, and higher risk animals e.g. cattle under 15 months of age with lower immunity (especially after weaning) or rising 2-3 year old cows under calving or nutritional stress.

Drenching and chemical resistance

There are currently three chemical groups of drench available for cattle in Australia. There are the macrocyclic lactones (-mectins), white drenches (benzimidazole and fenbendazole) and clear drenches (levamisole). A fully effective drench should reduce worm FECs by 95% in each worm species present in the animal at the time of testing. This means there is some important information Coopers want to know, including which drench you use and when. Therefore, when submitting you faecal samples, there will be an info sheet to fill out.


Recent studies in Victoria found that 66% of the 36 properties in the study had demonstrated resistance to at least one anthelmintic group. This worm resistance to drenches can result in significant production losses and possible stock death, and that is why it is important to determine whether there is any significant resistance in our local Fleurieu Peninsula! We are really keen to get this information so we can give the best advice possible.


From Coopers:

Ideally weaner age cattle should be tested prior to drenching at weaning and if a worm burden is diagnosed a repeat sample to be taken 12-14 days post treatment

If a long acting –mectin based drench is used at weaning repeat samples can also be taken at 30, 60, and 90 days post drenching

Please provide as much history as to the drenching history of weaners and the property as possible

If a lack of efficacy is seen with treatment, Coopers would be happy to get on farm and demonstrate the use of Trifecta orally if the producer is interested. We are also willing to test the efficacy of Trifecta post treatment.