Research Institute for Organic Agriculture, Frick

Control of gastrointestinal nematodes in cattle under dry pasture conditions

A controlled field experiment was performed in the year 2003 with 3 groups of each 20 first season grazing cattle. The efficacy of a biological (Duddingtonia flagrans) and an anthelmintic control strategy (morantel sustained release trilaminate bolus) against gastrointestinal nematodes (GIN) was investigated under unusually dry and warm meteorological conditions. The external conditions resulted in a substantial decrease of the infection risk on the experimental pastures, caused by direct (reduced migration of infective stages onto pasture, increased mortality rate) and indirect (reduced stocking rate, supplementory feeding) factors. Under these circumstances neither the chemical nor the biological strategy was necessary with respect to an additional limitation of the GIN infections. Largely unaffected by the parasite infections, the calves of the Duddingtonia, bolus and control group showed average daily weight gains of 688, 678 and 676 g respectively. The efficacy of D. flagrans against infective GIN larvae was demon­strated in coprocultures, performed at monthly intervals, showing a developmental rate of infective larvae of only 25 % compared to 83 % in the control group. Furthermore, during the final period of the experiment, the infection pressure on the pastures grazed by Duddingtonia-treated calves was approximately 90 % lower compared with the control group. In the context with data from various international studies the detection of D. flagrans in a soil sample of Switzerland is suggesting an ubiquitous occurrence of this species.

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