How do you mean? The case for composite faecal egg counts in testing for drench resistance

Abstract

Extract The faecal egg count reduction test (FECRT) is a procedure commonly employed for determining the anthelmintic resistance status of sheep farms in New Zealand. The number and types of anthelmintics to be tested may vary according to what is already known about resistance on the property concerned, but nowadays most FECRTs include at least four treatment groups (McKenna 2006). Obviously, the inclusion of so many treatments means that FECRTs can be expensive. However, substantial cost savings could be achieved by changes to the way that faecal egg counts (FECs) are carried out in such tests. Typically, FECs are performed on each animal in each treatment group. These individual FECs are then summed and divided by the number of samples examined, to provide an arithmetic mean egg count for the group concerned. Where only group mean egg counts are required for the analysis of results (as in the FECRT), however, a faster and cheaper outcome could be obtained by using a composite FEC technique. With the latter procedure, individual faecal samples from a group of animals are pooled and a single egg count carried out to deliver a mean figure.