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FFL-JA-Forskningsmidlene for jordbruk og matindustri

Mycotoxins and toxigenic fungi in Norwegian pig farming: consequences for animal health and possible intervention strategies

Awarded: NOK 0.60 mill.

One of the main objectives of the project was to test whether a commercial microbe is suitable for breaking down and releasing the mycotoxin deoxynivalenol (DON) in pig feed. In order to obtain basic data on the absorption and metabolism of the toxin in pigs, we conducted a study where we exposed piglets with pure deoxynivalenol and compared the results with laboratory tests where the substance was incubated with liver enzymes. The trial confirmed that pigs quickly excreted the toxin. In addition, it was shown that the laboratory model based on liver enzymes works very well to predict how the toxin is metabolized in a living organism. Such models could replace animal testing in many contexts. During 2014 extensive feeding trials with piglets were conducted, where the animals received an oat-based compound feed containing four different concentration levels of the mycotoxin deoxynivalenol from natural contamination. An equal number of animals were additionally added a deoxynivalenol-degrading microbe to the feed. One of the most important findings was that the microbe did not work under the conditions of the experiment and therefore appears unsuitable for Norwegian pig production conditions. This was an important clarification since this microbe is used as commercial feed additive in many countries. During the period December 2015 to February 2016 we have conducted feed trials with deoxynivalenol contaminated feed in sows during reproduction. The trial was conducted in a so-called pathogen-free farm in Kløfta/Norway. The sows received naturally contaminated feed, containing three different concentrations of DON, from about two weeks before birth of the piglets and until weaning. The concentration of DON in the feed was up to 1.7 mg/kg, which was well above the recommended limit values, both in Norway (0.5 mg/kg) and the EU (0.9 mg/kg). However, the study showed only moderate effects of the DON on the pigs and piglets. Sows who received DON in the feed ate less and had a reduction in feed consumption of up to 11% during late gestation and 10% in lactation compared with control sows. However, DON had no significant effect on body weight, fat contents, or reproductive performance, nor on measured blood parameters of the sows. Blood and milk samples were also taken from the sows and blood samples from a selection of piglets. This material showed a clear passage of DON from pregnant/lactating sows to newborn/nursing piglets. The transfer was more pronounced at birth, where DON went through the placenta rather than during lactation, where the toxin was transferred by the milk. In recent years, it has been shown that deoxynivalenol occurs in various forms in plants. For example, plants can change the molecule chemically so that one no longer detects the toxin with a common assay method. To learn more about the reactivity of deoxynivalenol, we have focused on the reaction of the substance with a group of compounds called thiols. Such substances occur frequently in nature, examples are the amino acid cysteine or the peptide glutathione. These are thiols that have important functions in many organisms, both plants and animals/humans. In the first step, we used the substance mercaptoethanol as a model molecule, optimized reaction conditions, and clarified which reaction products one receives with deoxynivalenol. We have tested the reaction with several other thiols, and have synthesized standards of deoxynivalenol-cysteine and deoxynivalenol-glutathione adducts. The reaction of deoxynivalenol with the amino acid cysteine has been used as a starting point in a patent application for treating cereal raw materials with thiols (such as cysteine) for chemical detoxification with deoxynivalenol. Recently we have detected DON conjugated to glutathione in Norwegian cereal grain, as well as several degradation products of such a conjugate (e.g. deoxynivalenol-cysteine). We have shown that such biotransformation products occur in plants, but their contribution to the total exposure to mycotoxin is unclear. In autumn 2014 and spring 2015 we have collected samples (air, different types of litter, dust, feed) in a selection of pig houses to map the presence of microfungi, endotoxins and mycotoxins as well as other fungal metabolites. Not surprisingly, the results showed that both the animals, but also the workers at the farm, are exposed to a variety of substances from microfungi and endotoxins (which is a degradation product from Gram-negative bacteria), including spores and fungal particles. Since the work was not part of any of the two doctoral dissertations that resulted from the project, the processing of the extensive data material has not yet been completed. This must be done in the post-project period.

The Norwegian pig farmers, feed industry and authorities require up-to-date knowledge on the occurrence and importance of mycotoxins and fungi in pork production. The present project is thus a holistic approach to elucidate the mycotoxin problem in Norweg ian pig farming, and involves collaboration between researchers from four Norwegian institutes, an Austrian institute and three industrial partners. It also includes training of two Norwegian PhD students. A comprehensive animal feeding study will be per formed investigating the effect of trichothecene-contaminated feed in suckling and weaned piglets and in farrowing/lactating sows with or without supplementation of the feed with a trichothecene-detoxifying commercialised microbe (Eubacterium BBSH 797). A nother part of the project will elucidate to which extend trichothecene-mycotoxins are conjugated or bound to matrix components, and thus are not necessarily detectable using routine analytical methods. This part will include the validation of commercial immunoassays. Finally, an in-depth survey of pig farms will provide data on endotoxin exposure of animals and humans, fungal diversity and occurrence of fungal metabolites/mycotoxins.

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FFL-JA-Forskningsmidlene for jordbruk og matindustri