Dynamics in the microbiology of maize silage during whole-season storage.

AIMS: To monitor seasonal variations in the microbiology of maize silage and to determine whether the risk of fungal spoilage varies during whole-year storage. METHODS AND RESULTS: A continuous survey of 20 maize silage stacks was conducted over a period from three to 11 months after ensiling. Filamentous fungi, yeasts and lactic acid bacteria (LAB) were enumerated at five time-points, and cultivable species of filamentous fungi were identified. Significant differences in the numbers of filamentous fungi, yeast and LAB were detected. The highest numbers of fungi were five to seven and the lowest 11 months after ensiling, while the LAB decreased in numbers during the study. Filamentous fungi were isolated from all stacks at all time-points. The most abundant toxigenic mould species were Penicillium roqueforti, Penicillium paneum and Aspergillus fumigatus. CONCLUSIONS: There are significant variations in the microbiology of maize silage over a whole storage season. The risk of fungal spoilage was highest 5-7 months after ensiling and lowest after 11 months. SIGNIFICANCE AND IMPACT OF THE STUDY: This information is valuable in the assessment of health risks connected with spoiled maize silage and may be useful in the management of maize silage stacks, when whole-season storage is applied.

Multi-mycotoxin analysis of maize silage by LC-MS/MS.

This paper describes a method for determination of 27 mycotoxins and other secondary metabolites in maize silage. The method focuses on analytes which are known to be produced by common maize and maize-silage contaminants. A simple pH-buffered sample extraction was developed on the basis of a very fast and simple method for analysis of multiple pesticide residues in food known as QuEChERS. The buffering effectively ensured a stable pH in samples of both well-ensiled maize (pH < 4) and of hot spots with fungal infection (pH > 7). No further clean-up was performed before analysis using liquid chromatography-tandem mass spectrometry. The method was successfully validated for determination of eight analytes qualitatively and 19 quantitatively. Matrix-matched calibration standards were used giving recoveries ranging from 37% to 201% with the majority between 60% and 115%. Repeatability (5-27% RSD(r)) and intra-laboratory reproducibility (7-35% RSD(IR)) was determined. The limit of detection (LOD) for the quantitatively validated analytes ranged from 1 to 739 microg kg(-1). Validation results for citrinin, fumonisin B(1) and fumonisin B(2) were unsatisfying. The method was applied to 20 selected silage samples and alternariol monomethyl ether, andrastin A, alternariol, citreoisocoumarin, deoxynivalenol, enniatin B, fumigaclavine A, gliotoxin, marcfortine A and B, mycophenolic acid, nivalenol, roquefortine A and C and zearalenone were detected.