Deoxynivalenol (DON) is one of most widespread mycotoxins in cereal commodities, and animal feed is prevalently contaminated at high concentrations. This poses a problem in animal nutrition as especially pigs are very sensitive to DON. An effective process for the reduction of the DON concentration is the treatment of contaminated feed with sodium bisulfite (SBS) whereby DON is transformed into DON-sulfonate (DONS). Although the success of this treatment has been confirmed in several feeding studies, it is unexplained if the decrease of DON is accompanied with a coincident increase of DONS. For this reason, we developed a method for the analysis of DONS using hydrophilic interaction chromatography coupled to tandem mass spectrometry. In order to investigate the correlation between DON and DONS concentrations during SBS-treatment, DON-contaminated wheat was treated with SBS and stored for up to 36 days. At defined timepoints of this treatment, samples were analyzed for DON and DONS using stable isotope labeled standards. The preparation, purification, and structure elucidation of DONS, and the HILIC-HPLC-MS/MS method for the analysis of DONS as well as the results of two storage experiments are presented in this paper.

No abstract

Unground triticale kernels contaminated with 6.63 mg deoxynivalenol (DON) per kg dry matter were stored for up to 63 days at total moisture contents of 13 and 15% in order to study the time-dependent kinetics of DON concentration in dependence on graded levels of sodium metabisulfite [0, 1, 2, 3, 4 and 5 g Na2S2O5 (SBS) per kg], and in the absence and presence of 10 g propionic acid (PA) per kg. The DON concentration decreased with increasing amounts of supplemented SBS and with increasing duration of the preservation period in a bi-exponential fashion when SBS addition was ≥3 g/kg. Lower SBS concentrations yielded inconsistent results. The maximum measured DON reductions after adding 5 g SBS/kg were 3 and 4% of the initial DON concentration after 63 days in the absence and presence of PA at moisture contents of 15%, while the corresponding recovery for the variants preserved at 13% amounted to 21 and 11%, respectively. The 12 variants preserved without PA supplementation were more frequently contaminated by moulds and yeasts (n = 5) than the corresponding variants stored together with PA (n = 1). The overall results and regressive evaluations do suggest that the highest SBS addition of 5 g/kg triticale at a moisture content of 15% preserved for 63 days would be necessary for a maximum DON reduction. Although PA did not exert a direct decontaminating effect, an additional supplementation together with SBS seemed to be advantageous with regard to the prevention of yeast and mould contamination and favouring the decontamination reaction by the acid milieu.

Mycotoxins are known to affect the health and performance of farm animals. In contrast to cereal grains, the straw is only rarely analysed for mycotoxins, although contaminated straw could additionally expose farm animals to mycotoxins. For this reason, two experiments were carried out to examine the effect of pre-harvest Fusarium infection (inoculation with F. culmorum) and different storage conditions on the mycotoxin concentrations in straw. In the first experiment, both the inoculated and the identically cultivated control straw were stored in rectangular bales either in a barn or outdoors for a time period of 32 weeks (farm-scale experiment). The second experiment was aimed to examine the mycotoxin concentrations during storage under controlled conditions in a temperature-controlled climatic chamber, with target dry matter contents of 86%, 82% and 78% using 1.5-l preservation jars (laboratory-scale experiment). While the concentration of deoxynivalenol and its derivates decreased in the farm-scale experiment when inoculated straw was stored outdoors, the zearalenone concentration increased within the same time period. The latter effect was also detected for the control straw. These opposite effects were probably caused by the massive water uptake during the outdoor storage. The only effect we observed in the laboratory-scale experiment with dry matter contents between 78% and 86% was a more pronounced decrease of the 3-acetyl-deoxynivalenol concentrations in the inoculated straw with increasing moisture contents.

Fusarium infections do not only affect the grain, but also the rest of the plant, which result in contamination of plants with the mycotoxin deoxynivalenol (DON). The bioavailability of DON may be influenced by the matrix due to the differences in nutrient composition between grain and straw, particularly the high fibre component in straw. The experiment was carried out by exposing 18 male castrated pigs (30-40 kg live weight) with a single dose of DON from wheat grain, straw and chaff in the diet. The courses of DON serum concentrations were evaluated using toxicokinetic methods. The absorption of DON was not influenced by the source of DON. The invasion half-life of DON from grain, straw and chaff amounted to 0.76, 0.77 and 0.48 h, respectively, and were not significantly different. The elimination of DON was also not affected by the DON source. The bioavailability of DON, calculated by the dose corrected area under the curve of the serum-DON-concentrations, amounted to 81.9, 87.3 and 109.8% for straw, grain and chaff, respectively, without significant differences. Thus, the uptake of DON from straw may contribute comparably to the overall exposure of animals.