Efficacy of oxfendazole as administered by intraruminal injection to naturally infected calves.

Oxfendazole, formulated into a 22.5% suspension, was administered by intraruminal injection to cattle at the rates of 0, 1.125, 2.25, 4.50, and 6.75 mg/kg of body weight. In total, 50 naturally infected calves were used, with 10 animals being allocated to each of the 5 treatment groups on the basis of pretreatment counts of nematode eggs per gram of feces. All animals were necropsied 7 days after treatment. The trial was done between December 1983 and January 1984, with the animals kept on concrete for a minimum of 35 days immediately before necropsy. For all nematodes and stages combined, efficacies were 97.4%, 98.8%, 99.5%, and 99.8% for oxfendazole at dosages of 1.125, 2.25, 4.50, and 6.75 mg/kg of body weight, respectively. Early 4th-stage larvae of Ostertagia and Nematodirus helvetianus adults were eliminated at rates greater than 93% only at the dosages of 4.50 mg/kg and above. Local or systemic adverse reactions were not observed in any of the animals.