Observations on the resumed development of arrested Ostertagia ostertagi in naturally infected yearling cattle

摘要: Abstract In three successive years, groups of yearling cattle were exposed in autumn to grazing infested with Ostertagia ostertagi . They housed at the end December and fate burdens arrested early fourth stage larvae which they had acquired was studied by means post mortem worm counts on animals killed intervals until summer. Arrested worms resumed their development a steady rate approximately 500 per day. Nearly all remaining March developed during that month. small number whose history condition suggested an impairment resistance, very large numbers January February led fatal disease.