Molecular characterization of gliotoxin-producing Aspergillus fumigatus in dairy cattle feed

Several strains of Aspergillus fumigatus produce mycotoxins that affect the health and productivity of dairy cattle, and their presence in dairy cattle feed is a serious concern. This study aimed to determine the densities of A. fumigatus and gliotoxin in commercial dairy feed.

More than 60 dairy feed samples were examined for fungal contamination, specifically for A. fumigatus, using phenotypic approaches and DNA sequencing of the internal transcribed spacer (ITS) and β-tubulin regions. Thin-layer chromatography and high-performance liquid chromatography (HPLC) were used to assess gliotoxin production in A. fumigatus. Real-time polymerase chain reaction (RT-PCR) was used to investigate the expression of gliZ, which was responsible for gliotoxin production. High-performance liquid chromatography was used to detect gliotoxin in feed samples.

Aspergillus was the most commonly identified genus (68.3%). Aspergillus fumigatus was isolated from 18.3% of dairy feed samples. Only four of the 11 A. fumigatus isolates yielded detectable gliotoxins by HPLC. In total, 7/11 (43.7%) feed samples tested had gliotoxin contamination above the threshold known to induce immunosuppressive and apoptotic effects in vitro. The HPLC-based classification of isolates as high, moderate, or non-producers of gliotoxin was confirmed by RT-PCR, and the evaluation of gliZ expression levels corroborated this classification.

The identification of A. fumigatus from animal feed greatly depended on ITS and β-tubulin sequencing. Significant concentrations of gliotoxin were found in dairy cattle feed, and its presence may affect dairy cow productivity and health. Furthermore, workers face contamination risks when handling and storing animal feed.