Ostertagia ostertagi drug abbreviated infections in calves and the development of protective immunity

Six month old calves kept on pasture were experimentally infected three times with O. ostertagi and 15 days later each infection was abbreviated with oxfendazole. After the immunisation period the animals were allowed to graze naturally contaminated pasture. The results obtained clearly show that immunised animals produced significantly fewer eggs than the non-immunised controls. The protection obtained was associated with increased daily liveweight gains.