The Eye of the Farmer and Detection of Animals in Need of Anthelmintic Treatment in Organic Meat Sheep Flocks

Organic meat sheep producers are limited by their access to and permitted use of synthetic drugs to effectively control internal parasites, and they are limited further still, by the narrow array of efficient alternative drugs available to them. The use of targeted selective treatments, for the control of parasites, e.g. treating only the lambs that cannot cope with infection, would be of interest. The difficulty is in identifying those specific lambs in need of treatment. FAMACHA © (an anaemia indicator) has been used with success in tropical areas where the blood sucking worm Haemonchus contortus is the main gastrointestinal nematode. From their own experience, farmers may also be able to detect lambs in poor, average or good condition, possibly relative to parasite infection burden, a method referred to as farmers' eye score. Using the farmers'eye score to judge lambs in need of treatment was not found to be fully efficient. It was however, significantly related to the presence of Moniezia eggs and to the number of Trichuris and possibly Nematodirus eggs in faeces but remained unrelated to the excretion of other gastrointestinal nematode eggs. The farmers'eye score was in agreement with the average faecal egg counts but the accuracy of individual detection of lambs in need of treatment, remained low (49% correctly classified). The FAMACHA © had an even lower efficiency to detect lambs requiring treatment. The farmers'eye score when correcting for farm variability was improved and highly correlated to the infection with Nematodirus. The farmers'eye score should be improved using pathophysiological indicators (diarrhoea score, weight gains..) or/and by harmonisation among farmers, if it is to be relied upon to detect animals in need of anthelmintic treatment in the future.