Detecting self-medication by grazing sheep against gastrointestinal nematodes

Abstract

Medicated feed blocks (MFB, containing an anthelmintic) could be used to control gastrointestinal nematodes (GIN) in sheep to achieve voluntary targeted selective treatment (TST) or self-medication. This would have the advantage of reduced selection pressure for anthelmintic resistance and reduced labour associated with providing treatment. The dynamics of MFB intake by sheep in a grazing environment are largely unknown because current techniques are not suitable for measuring supplement intake in grazing animals and/or measuring intake over a prolonged period. The experiments in this thesis were designed for two purposes. Firstly, to develop a technique that met the requirements of a marker of MFB intake for use over an extended period in grazing livestock. Secondly, to use this technique to determine if an MFB could be used to achieve voluntary TST by establishing if grazing sheep display self-medication in response to GIN infection.