[Investigations concerning bovine gastro-intestinal strongyles. II. Seasonal variations in the herbage infestation with infective larvae (author's transl)].

Ecological studies of bovine gastro-intestinal trichostrongylide larvae have been carried on during a three-year period (1972-1974). The studies mainly included pastures grazed by heifers (2nd time grazing cattle). Examination of the herbage samples was based on washing and filtration (sieve mesh-size 36 and 28 mu) followed by Baermann test on the debris. The pasture infestation with infective larvae (L3) followed a nearly stereotype seasonal pattern (cf. fig. 2 and fig. 3): A considerable larval population survived on the pasture during the winter, the infestation decreased strongly during April-May, was low during June and beginning of July, and increased from the middle of July to reach a peak in September-October. The infestation was usually much higher just around the faecal pats than in the rest of the pasture area (cf. fig. 3). The observed populations of trichostrongylide larvae were dominated by Ostertagia (ostertagi), but included other species as well, e.g. Cooperia (oncophora), Nematodirus spp., etc.