Pyrrolizidine alkaloids in commercial feedstuffs for horses.
Authors: Rückert C, Emmerich I, Hertzsch R, Vervuert I
Journal: Equine veterinary journal
Summary
# Pyrrolizidine Alkaloids in Commercial Horse Feeds: A Hidden Contamination Risk Pyrrolizidine alkaloids (PAs) are toxic plant compounds known to damage the liver in humans and various animal species, yet their presence in equine feedstuffs had not been systematically evaluated until this investigation. Researchers analysed 48 commercial horse feed products containing alfalfa or herbal blends using liquid chromatography-mass spectrometry to quantify 28 different PAs and assess contamination levels. Whilst 15% of samples fell below detectable limits, the remaining 85% contained measurable alkaloid concentrations, with a median of 58 µg/kg; critically, 43% of all samples exceeded the authors' calculated safety threshold of 90 µg/kg, and two alfalfa-based products contained dangerously high levels of 1306 and 1222 µg/kg respectively. The five most prevalent alkaloids identified were lycopsamine, seneciphylline, seneciphylline-N-oxide, senecionine and senecionine-N-oxide. Because equine-specific toxicity data for PAs remain unavailable, the researchers based their risk assessment on rodent and human studies, making the actual safety margins for horses uncertain and potentially inadequate. Equine professionals should be aware that standard commercial feeds pose a genuine contamination risk, particularly alfalfa-based and herbal products, and there is an urgent need for manufacturers to implement stricter quality control measures and for regulatory bodies to establish enforceable PA limits in equine feedstuffs.
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Practical Takeaways
- •Nearly half of commercial horse feed products analysed contained potentially unsafe pyrrolizidine alkaloid levels; feed selection and supplier verification are important preventive measures
- •Alfalfa-based and herb-containing feeds warrant particular scrutiny due to higher contamination risk; consider requesting pyrrolizidine alkaloid testing data from manufacturers
- •Monitor horses on contaminated feeds for signs of hepatotoxicity; establish industry standards and regulatory limits for pyrrolizidine alkaloids in equine feedstuffs
Key Findings
- •43% of 48 horse feed samples exceeded the calculated safe limit of <90 µg/kg for pyrrolizidine alkaloids
- •Median pyrrolizidine alkaloid concentration was 58 µg/kg with a range of 8-151 µg/kg (25th-75th percentiles)
- •Alfalfa-based feeds showed the highest contamination levels (up to 1306 µg/kg), with five alkaloids (lycopsamine, seneciphylline, senecionine, and their N-oxide forms) most frequently detected
- •The specific susceptibility of horses to pyrrolizidine alkaloids remains unknown, limiting extrapolation of safety thresholds from rodent and human data