Gastrointestinal nematode immunization trials in cattle

Three experiments were conducted to immunize calves against Ostertagia ostertagi, Trichostrongylus axei, and T colubriformis. Calves were given intraperitoneal injections with in vitro-grown parasitic larvae of the three species and IV and intraperitoneal injections of exoantigens obtained from culture media used to grow O ostertagi. None of the treatments provided immunity to subsequent oral challenge exposure with normal infective larvae.