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Faecal egg counts for herd health

Faecal egg counts

Senior Certification Officer, Stephen Smith talks about how to carry out a faecal egg count and what it could reveal.


What are faecal egg counts?

A faecal egg count (FEC) is a method of determining how many internal parasite eggs are present in a dung sample. It may also be possible to determine the different types of worms or other parasites present in the dung sample. The details for both the number and type of parasite can be used to determine whether or not an anti-parasitic treatment is required. FECs are also a useful tool to check for the presence of resistant worms. Resistance to the benzimidazole (white) and levamisole (yellow) wormer groups is common, particularly in sheep flocks in the UK.

How do you do it?

The first step is to collect fresh dung samples, ideally from ten or more separate droppings selected at random in the field. The samples need to be kept in separate containers / bags, and it is important to exclude as much air as possible. Once you have collected your ten samples, label each of them with which group of animals it was collected from and when it was collected. Ensure that the samples are kept out of sunlight in a cool place. The sample should be examined within 48 hours of collection. When preparing the samples for testing, portion out equal amounts or weights of each of the ten samples. These should be combined and tested as a single, collective sample. You may have the equipment on farm to carry out a count yourself, or you can use a service where you send away samples for analysis. Many vets are now able to offer a faecal egg count service for their clients.

Each separately managed group of animals should be tested in the above way.

What will the results show?

The average egg count will reflect the severity of the worm burden within the group and will help determine whether or not the animals should be treated. By testing groups of animals from particular fields / different holdings you may also be able to build up a picture of the potential worm infection risk from different areas of your farm which can be a useful consideration when making management decisions.

Some farmers implement a regular FEC test to identify individual animals that shed far fewer worms than the group average. The theory is that these animals will pass on the worm resistant traits to their offspring, with there being a decreased need for anthelmintic use over time.

Using FECs to check for resistance

The test can be used to check the efficacy of a specific anthelmintic and to determine whether there is any resistance to a particular wormer group(s). The simplest way of doing this is to collect ten individual dung samples from a group of livestock before carrying out the treatment.

The type of wormer used will determine the number of days after treatment that the second sample should be taken.

  • For benzimadazole (white drench) wormers the second sample should be taken 10–14 days post-treatment;
  • for levamisoles (yellow drench) seven days;
  • for avermectins and moxidectins 14–16 days.

The difference between the two test results will show the level of reduction that has been achieved. If the level of reduction is less than 95% (that is if more than 5% of the worms have survived) there is a potential resistance problem and you should take advice from your vet as to how to adapt your internal parasite control methods going forwards.

More information can be found at the following websites:

For any technical questions please ring:

  • For licensees: your certification officer or the producer certification team on 0117 9142412
  • For non-licensees 0117 314 5100