BIOLOGICAL-CONTROL OF TRICHOSTRONGYLES IN CALVES BY THE FUNGUS DUDDINGTONIA FLAGRANS FED TO ANIMALS UNDER NATURAL GRAZING CONDITIONS

The present study was conducted in the 1993 grazing season with yearli ng calves exposed to a pasture with a natural mixed trichostrongyle la rval infection. It was shown that daily feeding with the microfungus D uddingtonia flagrans during the first 2 months of the season led to a lowered herbage infectivity and a reduced acquisition of Ostertagia sp . and Cooperia sp. later in the season. In addition, the procedure del ayed the onset of clinical disease. This was due to the nematode-destr oying effects of the fungi in the dung excreted by the fungus-treated calves, as evidenced by results from a parallel in vitro assay on faec al larval cultures. The paper discusses future research needs before p ractical biological control can be implemented.