Effectiveness evaluation of several cattle anthelmintics via the fecal egg count reduction test.

Utilizing groups of cograzed, naturally infected beef-type heifers, three fecal egg count reduction tests were conducted in the later months of 2007 at the University of Arkansas. Each test was 28 days in length consisting of individual animal fecal nematode egg counts and coprocultures. Both original and generic ivermectin injectable formulations were used in two of the tests at 0.2 mg/kg BW, with FECR percentages never exceeding 90% in either test. Oral fenbendazole was evaluated at 5 and 10 mg/kg BW, with FECR%'s exceeding 90% on all occasions, but with a precipitous drop when recently treated animals were treated at the lower dose. Evaluated in one test, injectable moxidectin given at 0.2 mg/kg BW resulted in egg count reductions of 96-92% (days 7 to 28). Also evaluated in one test, albendazole delivered orally at 10 mg/kg BW was 98% and 97% effective at 17 and 28 days post-treatment. For all tests, coprocultures conducted post-treatment contained only Cooperia spp. larvae (benzimidazole use), relatively unmodified percentages of Cooperia spp. and Haemonchus spp. larvae (ivermectin use), and primarily Cooperia spp. larvae with a small percentage of Haemonchus spp. larvae (moxidectin use).