Filamentous fungi in wrapped forages determined with different sampling and culturing methods

Abstract

The use of wrapped forage bales with high dry‐matter (DM) content implies risk of fungal growth inside the wrapping, and impaired feed quality. Since fungi may be unevenly distributed in bales, the method of sampling can influence the outcome of the analysis. Three common sampling methods for detection of fungi in wrapped forage were compared: direct plating of visible mouldy patches on bale surfaces (Method I), direct plating of pieces of foliage from drilled core samples (Method II) and quantitative analysis dilution series of drilled core samples (Method III). All samples were cultured on two media at two temperatures. Samples were collected from 124 farms in Sweden and Norway. Using Methods I, II and III, fungi were detected on 52%, 77% and 56% of the farms respectively. Fifty‐two fungal species were identified using a combination of culturing and molecular methods. The most predominant species were Arthrinium spp., found on 55% of the farms, followed by Penicillium roqueforti at 48% of the farms. Incubation at 25°C resulted in higher numbers of all genera, except Aspergillus, compared to incubation at 37°C. The different methods of sampling and culturing did not identify the same fungal species within the same bale. Analysing one bale per farm resulted in detection of less than half the number of species compared to analysing three bales. Of the sampling and culturing methods compared, direct plating of drilled core samples cultivated at malt extract agar at 25°C performed best in terms of qualitative analysis of fungi species.

Occurrence of filamentous fungi and mycotoxins in wrapped forages in Sweden and Norway and their relation to chemical composition and management

“…Eight species of Fusarium were found in the samples from nine farms in the current study as reported in Schenck et al, (). Fusarium species have previously been identified in Norwegian bale silage by Skaar (), as well as in Irish bale silage (O’Brien et al, ; ), although in small amounts and in a small proportion of the bales (less than 10% of sampled bales).…”

“…The fungal species detected varied between the methods used and are reported in detail elsewhere (Schenck et al, ). On 110 of the 124 farms, a total of 52 fungal species were identified using all three sampling and culturing methods (Schenck et al, ).…”

“…The fungal species detected varied between the methods used and are reported in detail elsewhere (Schenck et al, ). On 110 of the 124 farms, a total of 52 fungal species were identified using all three sampling and culturing methods (Schenck et al, ). Of those, the mycotoxin producers belonging to the genera Aspergillus , Fusarium and Penicillium and the species Alternaria alternata and Paecilomyces varotia were selected to study the coexistence of fungus and mycotoxin (Table ).…”

“…Three bales from the same batch were randomly selected for sampling on each farm. For each bale, three different sampling methods were used, as described in full by Schenck et al (). Samples were pooled within each sampling method to produce one forage sample per farm and forwarded cooled for analysis within 24–48 hr.…”

“…In Method III, forage from sample cores was used for quantification of fungi by preparing tenfold dilution series cultured on MEA and DG‐18 plates and then incubated as described for Method II. All plates with fungal colonies were used for identification of species by ocular examination of macro‐ and microstructures using microscopes (LeicaM165FC fluorescence stereomicroscope and automated Leica DM5500B with differential interference contrast, and by DNA sequencing as described by Schenck et al ().…”