| Abstract: | In the course of studies on the control of bovine parasitic gastroenteritis in south west Scotland using a morantel sustained release bolus the populations of trichostrongyle infective larvae on herbage were monitored over a two-year period. From the results of the herbage analysis and the worm burdens in parasite naive tracer calves introduced at the end of 18 months, it was clear that considerable numbers of infective larvae of Ostertagia ostertagi and Cooperia oncophora survived for at least 18 months on pastures not grazed at all. The results suggest that in south west Scotland after one, or even two, seasons with no further contamination of grazing, permanent cattle pastures cannot be assumed to be helminthologically 'safe' and that this should be taken into consideration when determining prophylactic strategies. |
