Occurrence of mycotoxins and yeasts and moulds identification in corn silages in tropical climate

Abstract

Aims: This study was aimed to identify yeasts and moulds as well as to detectmycotoxin in corn silages in southern Minas Gerais, Brazil.Methods and Results: Corn silages from 36 farms were sampled to analyse drymatter, crude protein, ether extract, ash, neutral detergent fibre, nonfibrecarbohydrates and mycotoxins contents, yeasts and moulds population, pHand temperature values. The mycotoxins found in high frequency wereaflatoxin in 777% of analysed samples, ochratoxin (333%) and zearalenone(222%). There was no significant correlation between the mycotoxinconcentration and the presence of moulds. The pH was negatively correlatedwith ochratoxin concentration. Aspergillus fumigatus was identified in all silagesthat presented growth of moulds. Ten different yeast species were identifiedusing the culture-dependent method: Candida diversa, Candida ethanolica,Candida rugosa, Issatchenkia orientalis, Kluyveromyces marxianus, Pichiamanshurica, Pichia membranifaciens, Saccharomyces cerevisiae, Trichosporonasahii and Trichosporon japonicum. Another six different yeast species wereidentified using the culture-independent method.Conclusions: A high mycotoxin contamination rate (916% of the analysedsilages) was observed. The results indicated that conventional culturing andPCR-DGGE should be combined to optimally describe the microbiotaassociated with corn silage.Significance and Impact of the Study: This study provides information aboutthe corn silage fermentation dynamics and our findings are relevant tooptimization of this silage fermentation.