**Preface**

Zearalenone, deoxynivalenol, and their metabolites are among the most frequently encountered mycotoxins in plant materials. Their presence compromises the health quality of foodstuffs and feedstuffs, and increases the risk of ischemia and reperfusion injury, stress-related intestinal disorders, as well as endocrine, metabolic, and immune disorders. These problems are resolved on an individual basis by selecting the appropriate combination of measures. The symptoms and health consequences of high mycotoxin doses are generally known. However, small doses can cause disease without clinical symptoms or they can interact with the host body at various stages of life. Due to this ambiguous dose–response relationship, the symptoms associated with high mycotoxin doses cannot be easily extrapolated to low doses. The interactions between mycotoxins and between mycotoxins and physiological processes in cells, tissues, and microorganisms are also problematic. Mycotoxins present in feed come into direct contact with the intestinal mucosa. A healthy gastrointestinal tract comprises active cells and tissues with high-protein metabolic turnover rates. Cells and tissues are often targeted by mycotoxins. Some mycotoxins inhibit protein synthesis. For instance, deoxynivalenol ingested in small doses inhibits the uptake of substrates responsible for protein transport across intestinal walls. On the other hand, zearalenone has estrogenic properties, and low doses of this mycotoxin stimulate proliferative processes. Mycotoxins also influence the activity of local and general immune systems, and their adverse effects become manifested in immunosuppressed hosts. Mycotoxins can also suppress the host's immune system, thus increasing the risk of disorders caused by microorganisms, intestinal enzymes, and other toxins in the digestive tract without the clinical symptoms that are characteristic of mycotoxicoses.

Therefore, this study, presented in the Special Issue of *Toxins*, attempted to evaluate selected body systems and functional biomarkers of animals for varying doses of mycotoxins causing mycotoxicosis. I hope that the knowledge gained will deepen our understanding of the impact of mycotoxins on animal health and will facilitate decision-making in risk management.

The editors are grateful to all authors who contributed to the Special Issue. We would like to thank all expert peer reviewers for rigorously evaluating the submitted manuscripts. We are also grateful to the MDPI management team and staff for their valuable contributions, organizational input, and editorial support.

> **Maciej Gaj ˛ecki and Magdalena Gaj ˛ecka** *Editors*
