and in the biological control of nematodiosis in extensive bovine production system.

Cattle production in extensive systems favours the occurrence of gastrointestinal nematodes, and the use of nematophagous fungi complements the control strategies for these nematodes. The aim of this study was to evaluate the effectiveness of the fungi Arthrobotrys cladodes and Pochonia chlamydosporia in the biological control of gastrointestinal parasitic nematodes in grazing cattle. Twenty-four calves were randomly divided into four groups and allocated to independent paddocks from February 2018 to January 2019. In the first group, the animals received pellets containing P. chlamydosporia. In the second group, the animals received pellets containing A. cladodes. In the third group, the animals received pellets containing a combination of the fungi A. cladodes and P. chlamydosporia. In the control group, the animals received pellets without fungus. The combined use of A. cladodes and P. chlamydosporia showed greater efficacy in the biological control of bovine gastrointestinal parasitic nematodes than the same fungi used separately. The parasite load was lower and weight gain was greater (P ⩽ 0.05) in the groups of cattle treated with nematophagous fungi. Therefore, the use of A. cladodes and P. chlamydosporia is promising in the biological control of nematodiosis in cattle.