Is your dewormer working?

The difference Safe-Guard (fenbendazole) makes.

Is your dewormer working?

The costs for anthelmintic resistance in your cattle – dairy and beef – are too high to ignore. Ask yourself how much reduced weight gain, lower milk production, decreased reproductive performance and increased incidence of disease would cost your operation?

Take the test

So how do you know if there is a potential parasite resistance with your current dewormer? You can find out with the Fecal Egg Count Reduction Test (FECRT), the standardized diagnostic tool developed with the input and support of leading cattle veterinary parasitologists1.

Which animals should I sample?

For best results, sample animals from the same age group. The ideal is cattle 6 months to 2 years of age:

  • Cow-calf: Sample from pastured cattle of the same age and management group.
  • Incoming cattle- stocker/feedlot/ replacement heifers: Test and treat on arrival to check incoming parasite population.
  • Stocker/replacement heifers on permanent pasture: Test resident cattle after sufficient grazing time (at least 2 months). Sample from pastured cattle of the same age and management group.
  • Dairy: Sample from replacement heifers of the same age and management group.

How many animals get sampled?1

  • 20 random animals within a defined group will provide a statistically adequate sample to represent the population’s average egg shedding.

What samples are needed?

Conduct the field test during optimal parasite transmission on your pasture.

  • 20 random, individual fecal samples taken at treatment day (identified as PRE TREATMENT GROUP).
  • 20 random, individual fecal samples taken 14 days post treatment (identified as POST TREATMENT GROUP).

How do I gather samples?

  1. Sample as directed by cattle veterinarian.
  2. Collect rectal or observed freshly dropped sample;
    • Use a re-sealable sandwich-size bag for each sample.
    • Invert bag and collect golf ball-size sample.
    • Re-invert bag, squeeze air out and seal (check seal).
    • Identify sample by date collected and animal group with permanent marker on the bag.
  3. Put individual samples from each group in larger resealable bag and identify by date and animal group, if testing more than one group.
    • Keep sample groups separated.
  4. Individual samples only – do not mix or pool samples from different animals.
  5. Refrigerate overnight to ensure each sample is sufficiently cooled. DO NOT FREEZE.
  6. Work with your local veterinarian to determine who will conduct FECRT test
  7. Pre-and post-treatment samples need to be sent to the same lab.
  8. Ensure lab uses Modified Wisconsin sugar float or Double Wisconsin sugar float procedure.

How are the results evaluated?

To calculate the efficacy of your dewormer, use the following formula:

((Pre-treatment average worm egg count - Post-treatment average)/Pre-treatment count) X 100

What happens then?

If the efficacy of the anthelmintic falls below 90 percent after completing the proper testing protocol:

  1. Consider additional diagnostic investigation (discuss with your veterinarian).
  2. Use an alternate treatment.
    1. Use a different class of anthelmintic or combination of 2 compounds of different class:
      • Benzimidazoles: albendazole, fenbendazole, oxfendazole.
      • Endectocides: doramectin, eprinomectin, ivermectin, moxidectin.
      • Imidazoles: levamisole, morantel tartrate.
    2. Repeat screening test under new treatment

Where should I send samples to?

For more information, contact your local veterinarian or Merck Animal Health sales representative.


1USDA’s parasite National Animal Health Monitoring System (NAHMS) Study 08 and roundtable