Anthelmintic efficacy of febantel against gastrointestinal helminths in calves.

Three dosage levels of febantel were tested for anthelmintic activities in calves under field conditions. A total of 20 feeder calves affected with naturally occurring gastrointestinal parasites were used in the controlled test. The calves were allotted to 4 groups of 5 each on the basis of degree of parasitism, body weight, age, and sex. Calves in groups II through IV were treated with febantel paste formulation at dosage levels of 5, 7.5, and 10 mg/kg of body weight; calves in group I were used as nonmedicated controls. Calves were euthanatized and necropsied 7 days after treatment. Medications were 97% to 100% effective against the adult forms of Haemonchus placei, Trichostrongylus axei, Cooperia pectinata, C oncophora, Nematodirus spathiger, and Oesophagostomum radiatum; 93% to 98% against Ostertagia ostertagi; and 78% to 95% against Trichuris sp. There were no differences in efficacies of the 3 dosage levels used against adult worms. Efficacy varied from 61% to 96% against larvae of O ostertagi. Activity was not detected against the tapeworm Moniezia benedeni. Medicated cattle did not show signs of intoxication.