Fecal egg count test results are a snapshot in time of the parasite level in an animal.
Jerry Woodruff, veterinarian with Boehringer Ingelheim Vetmedica, Inc., says there are several factors that can lead to an incorrect conclusion when interpreting fecal egg count results.
One factor that can lead to an incorrect conclusion is failing to take enough samples. Fecal egg counts vary greatly within a group of animals, so if an inadequate number of samples are analyzed, you won’t get a true picture of the parasite level.
To get a good idea of what you’re dealing with, gather 20 manure samples, or 10 percent of the group, in herds larger than 200 head.
Source: Bovine Veterinarian