Studies on the Effect of Temperature, Incubation Time and in vivo Gut Passage on Survival and Nematophagous Activity Arthrobotrys oligospora Var. Oligospora and A. cladodes Var. Macroides

This work was carried out to study effects of important environmental factors including temperature, incubation time and gut passage on nematophagous activity of Arthrobotrys oligospora var. oligospora and Arthrobotrys cladodes var. macroides against Haemonchus contortus. H. contortus third stage larvae (L3) were added to the fungal cultures in Petri-dishes and incubated for 24-96 hours at 15-25°C. The nematophagous potential of the fungi was determined by counting the number of viable L3 using Baermann technique. Dung pat bioassay and fecal culture techniques were used for testing the viability and nematophagous activity of the fungi after gut passage through calve in a mixture with barley grains. Results indicated that both tested fungi were able to survive at all temperatures and incubation times and no differences were reported for their nematophagous activity in this regard. Also, predacious activity of fungi after gut passage in reduction of L3 of H. contortus were 79.7 and 83.3% in faecal cultures method, and 85.4 and 78.8% in dung pat bioassay method, respectively. In conclusion, these native fungi are promising for use in biological control of gastrointestinal nematodes of ruminants under field conditions.