Evaluation of administering Duddingtonia flagrans through Complete Feed Block for Controlling Haemonchus contortus in Sheep

In this experiment, a device was developed and evaluated to deliver nematophagous fungus Duddingtonia flagrans to sheep by using local fungal isolate. Sterilized barley grains supporting the fungal growth were incorporated into straw based complete feed blocks (CFB). The viability of fungal spores was assessed for the biological control of ovine Haemoncus contortus. Two groups (fungus-treated and control without fungus), each consisting of five Garole x Malpura lambs (about 6-9 months old) which were artificially infected with 6000 Haemonchus contortus larvae per lamb. The treated group received fungus incorporated CFB (400g block per lamb delivering 6 million chlamydospores) daily during 7 weeks. Fungal chlamydospores survived well in CFB with very little moisture (11.8%) when stored at room temperature. Mean larval development was significantly (P<0.001) lower compared to control from day 1 to the end of the feeding. Larval recovery from the grass samples started from 2nd week of the experiment, and it increased markedly on the plot grazed by the control group reaching as high as 4000 L-3/kg DM compared to less than 600 L-3/kg DM in the plot grazed by experimental group fed on CFB with fungal spores. No significant difference was observed in the number of eggs per gram of faeces between both the groups. However, significant (P<0.001) reduction in developed larvae on coprocultures was seen for fungal spore incorporated group. A low level of larval counts were maintained in the plot grazed by fungus treated group throughout the experiment. The study demonstrated that CFB feeding might prove a potential means of delivery of D. flagrans to sheep for successful biological control of H. contortus.