Seasonal changes of gastrointestinal nematode populations in yearling beef cattle in Louisiana with emphasis on prevalence of inhibition in Ostertagia ostertagi.

摘要: Abstract Investigation of seasonal changes in the composition nematode populations, principally Ostertagia oslertagi , was conducted over 3 years at three locations Louisiana. This is most commonly occurring parasite cattle state. Naturally infected yearling were killed monthly extended periods and tracer calves grazed for intervals from late autumn to summer two 1978–1979. Major objectives determine incidence common gastrointestinal nematodes O. ostertagi particular, time period during which larval inhibition prevalent, circumstances under larvae conditioned inhibition, duration inhibition. Small numbers inhibited recovered between November February. Large found initially March increased April May. Both normally developing prone acquired winter-early spring, with proportion latter being more prevalent Evidence indicated that few after early June. burdens persisted through summer; adults minimal. Maturation occurs August October one instance associated cases clinical parasitism. Factors responsible not defined, but increasing temperatures host resistance, density-dependence populations considered. Other abomasal genera spring while intestinal spring.