The load of mycotoxins, phytoestrogens, pesticides and other toxins in a broad range of feedstuffs and implications for horse health

This thesis investigates the prevalence of contaminants in horse feed and their potential implications for equine health. A total of 108 feed samples, including hay, grains, processed plant products, and supplementary feeds, were collected across Europe and analyzed for over 250 contaminants using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The study aimed to assess contamination levels, identify differences among feed types, and evaluate the potential health risks posed to horses. Findings revealed that 99 % of the samples contained fungal metabolites, with Fusarium toxins being the most prevalent. High concentrations of phytoestrogens and plant toxins were observed, particularly in lucerne-based and mixed processed plant products, raising concerns about their potential cumulative health effects. Single feed products like hay exhibited lower contamination levels compared to supplementary feeds such as grain-free mashes and mueslis. Additionally, pesticide and veterinary drug residues were detected, with mash products showing the highest contamination load. The study highlighted significant regulatory gaps, as current EU guidelines primarily focus on farm animals and inadequately address contaminants in horse feed. Hazardous substances like colchicine and monensin, which are toxic to horses, were identified in several samples, likely due to cross-contamination during production. The thesis underscores the need for stricter regulations, routine testing, and targeted research to better understand the synergistic effects of co-contaminants. These measures are crucial for ensuring the safety of horse feed and safeguarding equine health