**Nicole Reisinger 1, Sonja Schürer-Waldheim 1, Elisabeth Mayer 1, Sandra Debevere 2,3, Gunther Antonissen 2,4, Michael Sulyok <sup>5</sup> and Veronika Nagl 1,\***


Received: 12 September 2019; Accepted: 1 October 2019; Published: 4 October 2019

**Abstract:** Forages are important components of dairy cattle rations but might harbor a plethora of mycotoxins. Ruminants are considered to be less susceptible to the adverse health effects of mycotoxins, mainly because the ruminal microflora degrades certain mycotoxins. Yet, impairment of the ruminal degradation capacity or high ruminal stability of toxins can entail that the intestinal epithelium is exposed to significant mycotoxin amounts. The aims of our study were to assess (i) the mycotoxin occurrence in maize silage and (ii) the cytotoxicity of relevant mycotoxins on bovine intestinal cells. In total, 158 maize silage samples were collected from European dairy cattle farms. LC-MS/MS-based analysis of 61 mycotoxins revealed the presence of emerging mycotoxins (e.g., emodin, culmorin, enniatin B1, enniatin B, and beauvericin) in more than 70% of samples. Among the regulated mycotoxins, deoxynivalenol and zearalenone were most frequently detected (67.7%). Overall, 87% of maize silages contained more than five mycotoxins. Using an in vitro model with calf small intestinal epithelial cells B, the cytotoxicity of deoxynivalenol, nivalenol, fumonisin B1 and enniatin B was evaluated (0–200 μM). Absolute IC50 values varied in dependence of employed assay and were 1.2–3.6 μM, 0.8–1.0 μM, 8.6–18.3 μM, and 4.0–6.7 μM for deoxynivalenol, nivalenol, fumonisin B1, and enniatin B, respectively. Results highlight the potential relevance of mycotoxins for bovine gut health, a previously neglected target in ruminants.

**Keywords:** modified mycotoxin; co-occurrence; corn silage; CIEB; WST-1; NR; SRB; sphingolipid metabolism; Sa/So

**Key Contribution:** By analyzing 158 samples from 10 different countries, we provide a comprehensive overview on mycotoxin contamination patterns in European maize silages. For the first time, the cytotoxicity of frequently occurring Fusarium toxins was determined on bovine intestinal cells, resulting in a toxicity ranking of NIV > DON > ENNB > FB1.
