Atypical myopathy-associated hypoglycin A toxin remains in sycamore seedlings despite mowing, herbicidal spraying or storage in hay and silage.
Authors: González-Medina S, Montesso F, Chang Y-M, Hyde C, Piercy R J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Hypoglycin A Persistence in Sycamore Material Atypical myopathy (AM) remains a significant seasonal threat to grazing horses, particularly in autumn and spring when sycamore seedlings proliferate. This study investigated whether commonly recommended pasture management interventions—mechanical mowing and herbicidal treatment—could reduce hypoglycin A (HGA) toxin levels in sycamore seedlings, and whether processing contaminated material into hay or silage might render it safe. Using validated LC-MS analysis, researchers tracked HGA concentrations in mowed or sprayed seedlings over two weeks, examined cross-contamination of adjacent grass, and tested sycamore material stored within hay and silage for six to eight months. The findings were sobering: neither mowing nor herbicidal spraying (using dimethylamine or picolinic acid-based products) produced any significant reduction in HGA content, and mowing actually caused a temporary spike in seedling toxin levels, presumably due to plant stress responses. Grass cut alongside mowed seedlings showed measurable HGA contamination within one week, confirming cross-contamination risk. Most critically, HGA persisted in both hay and silage storage for months, meaning that contaminated herbage preserved through fermentation or drying retains its toxicological threat. For practitioners, these results demand a shift in pasture management strategy: mechanical removal of sycamore seedlings prior to mowing—rather than simultaneous cutting—offers the best current protection, and pastures with known sycamore contamination should be excluded entirely from forage production. Supplementary feeding or alternate grazing during high-risk seasons remains essential where contamination cannot be eliminated.
Read the full abstract on PubMed
Practical Takeaways
- •Do not rely on mowing or herbicide spraying to eliminate hypoglycin A risk from pastures—these interventions are ineffective and mowing may temporarily increase toxin levels
- •If sycamore seedlings are present in pastures, mechanically collect and remove them entirely rather than mowing in situ, and keep removed material away from stored forage operations
- •Never use hay or silage from pastures contaminated with sycamore seeds or seedlings, as toxin persists through fermentation and storage for months and remains an intoxication hazard
Key Findings
- •Mowing sycamore seedlings did not significantly reduce hypoglycin A (HGA) content and temporarily increased HGA levels
- •Herbicidal spraying (both dimethylamine-based and picolinic acid-based) failed to reduce HGA concentration in seedlings over 2 weeks
- •HGA concentration increased significantly in grass cut together with sycamore seedlings by 1 week post-cutting, indicating cross-contamination risk
- •Hypoglycin A remained detectable in sycamore seeds and seedlings after 6-8 months storage in hay or silage, posing ongoing toxicity risk