University of Veterinary Medicine Vienna Exposure of horses to biotoxins, phytoestrogens, and pesticides from different feed materials and supplementary feeds Background The occurrence of biotoxins and chemical residues in marketed horse feeds has direct influences on horse health but has not been studied yet. Aims/objectives The study investigated the exposure and health implications of contaminants in various horse feedstuffs available on the European market. Methods A total of 108 feed samples representing diverse product categories such as hay, processed roughage products, grains, and various supplementary feeds were collected from different European countries and analyzed for contaminants, including mycotoxins, phytoestrogens, pesticides, and veterinary drug residues using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results Findings revealed that nearly all samples contained multiple fungal metabolites, with Fusarium toxins being the most prevalent. Processed roughage products (e.g., cobs, cubes, flakes and pellets) containing lucerne exhibited high concentrations of phytoestrogens and plant toxins compared to hay. The data also showed that supplementary feeds, particularly grain-based mueslis and mashes, were more prevalent sources of pesticide and veterinary drug residues than feed materials. Unusual substances in horse feed like colchicine and monensin, both highly toxic to horses, were also detected in roughly 10 to 20 % of the samples. However, our risk assesement suggests that the contamination of both compounds would not pose an acute health risk to horses. Conclusions The study reveals the complexity of biotoxins and chemical residues and their potential risks in marketed equine feeds and underscores the critical need for targeted regulations, routine testing to ensure equine health and welfare. en TEXT journal article Wissenschaftlicher Artikel Articolo di rivista Text journal article Testo Articolo di rivista Text Wissenschaftlicher Artikel Ergot Alkaloids Horse Feeding Horse Health Mycotoxins Veterinary Drug Resistance 2025 2025 Ratchaneewan Khiaosa-Ard L. M. Kwass Qendrim Zebeli M. Sulyok V. Milojevic Barbara Metzler-Zebeli Elsevier