Predation of the fungus Duddingtonia flagrans on infective larvae of gastrointestinal nematodes from heifers in a silvopastoral system under shaded and sunny conditions

The objective of this study was to evaluate the predatory activity of the nematophagous fungus Duddingtonia flagrans on infective larvae of gastrointestinal nematodes from dairy heifers in different conditions (shaded and sunny) of a silvopastoral system (SPS) on an agroecological farm. Ten Jersey heifers were divided into two groups: treated (received pellets containing fungus); and control (received pellets without fungus). Twelve hours after fungus administration, faeces samples were collected for in vitro efficacy tests. The animals then remained for 8 h in the experimental pasture area. At the end of this period, 20 faecal pads (10 treated and 10 control) were selected. Pasture, faecal pad and soil collections occurred at intervals of seven days (d), totalling four assessments over 28 d. To evaluate the influence of the conditions shaded and sunny, we registered the condition of the location of each faecal pad per hour. After 12 h of gastrointestinal transit in dairy heifers, a reduction of 65% was obtained through the in vitro test. The treated group presented a lower number of infective larvae (L3) in the faecal pad and upper pasture. Differences in numbers of L3 were observed between the conditions (sunny and shaded) in the faecal pad of the control group; while in the treated group there were no differences between the conditions. The predatory activity of the fungus was efficient over time in the shaded and sunny conditions of an SPS, decreasing the parasite contamination during the pasture recovery time in a subtropical climate.