Comparison of ruminant anthelmintics, using multiple dose administration

Eleven ruminant anthelmintics were administered to lambs over a 30-day period, using medicated feeds or multiple oral doses. Fenbendazole and its sulfinyl analog, oxfendazole, were effective (greater than 90%) in the control of clinical parasitism at feeding levels of 5 mg/kg of feed. Parbendazole and albendazole were effective at daily oral dose levels of 1 mg/kg of body weight and at feeding dose levels of 10 mg/kg of feed, respectively. Levamisole, mebendazole, and oxibendazole were ineffective in controlling intense natural parasitic infections of sheep at daily oral dose levels equal to or less than 1 mg/kg of body weight and/or a feeding level equal to or less than 10 mg/kg of feed.