Control of infective larvae of gastrointestinal nematodes in heifers using different isolates of nematophagous fungi.

The effect of different nematophagous fungi [Duddingtonia flagrans (AC001 and CG722) and Monacrosporium thaumasium (NF34)] with regard to controlling infective larvae (L3) of nematodes after gastrointestinal transit in female cattle (3/4 Holstein × Zebu) was evaluated. A total of 24 pubescent female cattle were used, weighing approximately 320 kg each one. There were three treatment groups, each contained six animals that received 150 g of pellets (0.2 g of mycelium), orally in a single dose, in a sodium alginate matrix containing mycelial mass of the fungus D. flagrans (AC001 or CG722) or M. thaumasium (NF34); and one control group (without fungi). Fecal samples were collected from the animals at intervals of 12, 15, 18, 21, 24, 48, and 72 hours. At the end of 17 days, the L3 not subjected to predation were recovered by means of the Baermann method. The fungal isolates tested were capable of destroying the L3 after gastrointestinal transit. It was observed that within 72 hours, the isolates AC001, CG722, and NF34 showed a higher predatory activity (81.2%, 97.3%, and 98.3%, respectively). The results justify the need for studies in the field, and over longer intervals, in order to observe the efficiency of the fungus D. flagrans, or even M. thaumasium, for environmental control over nematodes in naturally infected cattle.