Anthelmintic efficacy: The topic of anthelmintic resistance is one that is slow to generate interest among farmers, with many often ignoring the risks until it is too late. There are growing levels of resistance being identified at farm level to the three commonly used anthelmintic classes – benzimidazole or white drench, levamisole or yellow drench and macro cyclic lactones or clear drench including ivermectins.

If in doubt that this is an issue in your flock, it is important to carry out tests. The most straightforward method which was used previously in the sheep technology adaption programme includes carrying out a faecal egg count followed by treating sheep with the anthelmintic in question and then carrying out another faecal egg test to determine if a sufficient kill of worms has been achieved.