Evaluation of the anthelmintic efficacy of an ivermectin controlled-release capsule in lambs under field conditions in Europe

Three field trials were conducted in Germany, Slovakia and UK to evaluate t he anthelmintic efficacy and productivity responses attributable to treatme nt of lambs with an intra-ruminal controlled-release capsule which is desig ned to deliver ivermectin at 0.8 mg/day for 100 days to lambs weighing 20-4 0 kg at treatment. Sixty Merino Landrace, 60 Valaska or 52 Suffolk cross la mbs weighing between 24.0 and 40.0 kg at the time of treatment were used. L ambs were either untreated (or subjected to salvage treatment) or they rece ived an ivermectin controlled-release capsule. Faecal egg and larval counts of various nematodes, body weights and scores of the faecal soiling of the breech area (formation of dags) were determined before treatment and at 28 , 56, 84, 98 and 112 days after treatment. Before treatment, faecal strongy le, Nematodirus and Trichuris egg counts and Dictyocaulus filaria larval co unts were not significantly different (P > 0.05 or P > 0.1) between groups, but at each point of time thereafter, egg and larval counts of the ivermec tin controlled-capsule treated lambs were significantly reduced compared to the untreated controls. Lambs treated with the ivermectin controlled-relea se capsule gained significantly more weight (10.9, 11.1 or 11.1 kg, respect ively) over the 112 days of the trials compared to untreated lambs (8.2, 9. 7 or 5.5 kg, respectively). The mean scores of faecal soiling were not diff erent at the start of the trials (P > 0.05 or P > 0.1), but at the end of t he trials, the ivermectin controlled-release capsule treated lambs had sign ificantly lower scores of faecal soiling than the controls. (C) 1999 Elsevi er Science B.V. All rights reserved.