Abstract
Gastrointestinal nematodes are among the most significant parasites affecting livestock health and productivity, leading to major economic losses and contributing to the global increase in resistance to anthelmintics. Biological control using fungi with ovicidal and nematophagous activity offers an environmentally friendly alternative. This trial represents the first long-term field evaluation in cattle of the commercial combination of D. flagrans and P. chlamydosporia under natural infection conditions. Eighteen Holstein × Zebu males (12-15 months old) were divided into three groups (n = 6): T1 (D. flagrans), T2 (D. flagrans + P. chlamydosporia), and control. Treatments were administered orally daily (6 g/100 kg BW of each fungus; 10(6) chlamydospores/g) for nine months. Fecal egg counts (EPG) and infective larvae in pasture (L3) were monitored. Groups T1 and T2 showed significantly lower EPG values than the control during most of the experimental period. Haemonchus spp. was identified as the predominant nematode, supporting its epidemiological relevance. The combined fungal treatment exhibited enhanced effectiveness, enhancing parasite suppression through complementary ovicidal and larvicidal mechanisms. This approach offers a sustainable alternative to the excessive use of chemical compounds and has the potential to contribute to integrated animal health and livestock production.