The levels of zearalenone and its metabolites in plasma, urine and faeces of horses fed with naturally, Fusarium toxin-contaminated oats.
Authors: Songsermsakul P, Böhm J, Aurich C, Zentek J, Razzazi-Fazeli E
Journal: Journal of animal physiology and animal nutrition
Summary
# Editorial Summary: Zearalenone Metabolism in Horses Fed Contaminated Oats When horses consume Fusarium-contaminated feed, understanding how they process mycotoxins is crucial for assessing genuine health risk versus theoretical concern—particularly given equines' apparent resistance to zearalenone (ZON) compared with other species. Songsermsakul and colleagues fed horses naturally contaminated oats and tracked ZON and its metabolites across plasma, urine and faecal samples over a 10-day period, using chromatographic analysis to identify and quantify each compound. Plasma concentrations of β-zearalenol (the primary metabolite) peaked at 3.21–6.24 µg/l by day 10, whilst faecal matter contained the parent ZON alongside both α- and β-zearalenol isomers; notably, horses performed extensive glucuronidation of metabolites in urine and plasma (approximately 100%) but minimal conjugation in faeces (4–15%). The marked metabolic shift towards β-zearalenol production—rather than the oestrogenic α-zearalenol isomer that predominates in swine—likely underpins the horse's natural resistance to ZON toxicity, suggesting contaminated oats pose considerably less reproductive or systemic risk than equivalent exposure in other livestock. This finding should reassure practitioners that whilst feed testing remains prudent, moderate ZON contamination in equine forage warrants less aggressive management intervention than protocols designed for porcine or poultry operations.
Read the full abstract on PubMed
Practical Takeaways
- •Horses are naturally resistant to zearalenone toxicity due to their metabolic conversion pathway, but contaminated feed should still be avoided as metabolites are present systemically
- •Monitor feed quality for Fusarium contamination regardless of species differences in susceptibility, as horses still absorb and metabolize the toxin
- •Understand that metabolite profiles differ between species—findings from swine toxicology studies may not directly translate to equine risk assessment
Key Findings
- •β-zearalenol was the predominant metabolite detected in horse plasma (3.21-6.24 μg/l on day 10), urine, and faeces following consumption of naturally contaminated oats
- •Horses achieve approximately 100% glucuronidation of zearalenone metabolites in urine and plasma, but only 4-15% in faeces
- •Horses preferentially convert zearalenone to β-zearalenol rather than α-zearalenol, which explains their lower susceptibility to zearalenone compared to swine
- •Zearalanone was also detected as a minor metabolite in urine (1.34-5.79 μg/l) and faeces (1 μg/kg)