The toxigenic fungal moulds Penicillium, Fusarium and Aspergillus have previously been identified in silages and these moulds, whose activity in feeds can be unevenly distributed, can produce the secondary metabolite mycotoxins. Mycotoxins can exert a range of detrimental effects on livestock including reproductive disorders, organ damage, immunosuppression and lameness. To accurately assess the risk posed to livestock by mycotoxins in feed, an UHPLC-MS/MS analytical method, capable of detecting 20 mycotoxins in a single assay and inclusive of all eight EU regulated mycotoxins, was developed, validated and successfully applied to silage samples. Constituents within silage can be unevenly distributed, and collecting a representative sample may thus be challenging. Therefore, the variability in conventional chemical and mycotoxins characteristics in the next-to-be-fed pit section or bale of silage was quantified and an assessment made of the intensity of sampling that was required. Collecting a representative core sample from silages for conventional chemical characteristics was feasible (2-4 cores), whereas representatively sampling for mycotoxin analysis could require an order of magnitude more intensive sampling, and this might not be practical in practice (e.g. up to 128 cores per bale for some mycotoxins). In contrast, intensive sampling of chopped and mixed silages from the feed trough produced both baled and pit silage samples that could be analysed to provide a reasonably reliable estimate of conventional chemical composition and, under the prevailing circumstances, of mycotoxins type and concentrations. This study also characterised the mycotoxin challenge presented to livestock by the next-to-be-fed pit section or bale of silage. Two separate surveys were conducted in January - February 2012 (pilot survey) and December 2012 - March 2014 (national survey) to identify and quantify the mycotoxin incidence and concentrations on the next-to-be-fed pit section or bale of silage. Fusarium-produced zearalenone was detected in the national survey study, although this was only in Year 2. The increased incidence of zearalenone in Year 2 coincides with the daily maximal monthly (July) air temperatures of 22°C, which is the optimal temperature for Fusarium fungal development. Zearalenone was detected in pit and baled grass silages and pit maize silage but only in a total of 1 % of national survey samples. The maximum zearalenone value recorded was 76 ug/kg DM and this was less than 4 % of the EU regulated threshold. The most common mycotoxins detected were the Fusarium-produced enniatins and beauvericin. These were most likely formed during crop growth (Le. pre-mowing). They were, however, found in all silage types and were at relatively low concentrations, with mean concentrations of individual enniatins ranging from 9.1 to 364 ug/kg OM. The incidence of these mycotoxins tended to be elevated when the harvested grass crops were produced over a more extended duration. They were thus associated with low silage DMD that was indicative of a crop harvested at a later, more advanced growth stage, and also with a later month of harvest. The post-mowing Penicillium-produced mycotoxins (andrastin A, mycophenolic acid and roqueforline C) were most commonly detected in baled grass silage, and although their overall incidence was low, there was a large range in their mean concentrations. For example,mycophenolic acid ranged from 287 to 11,157 ug/kgDM. Post-mowing mycotoxins in this study were positively related to the presence of visible mould colonies on silage bales and to the presence of rotted silage in pit silages.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:695670 |
| Date | January 2015 |
| Creators | McElhinney, Cormac |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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