Little evidence that Beach Pea (Lathyrus japonicus) toxins cause gait abnormalities in Sable Island Feral Horse (Equus ferus caballus)

Résumé

Lathyrus is a leguminous plant genus notable for its synthesis of lathyrogens, a group of nonprotein amino acids. Lathyrogens can have a range of toxic effects on mammals when consumed in large quantities, but research on lathyrogens has occurred primarily in an agricultural context and on the syndromes (osteo-, angio-, and neuro-lathyrism) that Lathyrus consumption causes in humans and livestock. We know relatively little about whether the lathyrogens in uncultivated Lathyrus species are more broadly consequential to the ecology of natural ecosystems. For example, the unmanaged Feral Horse (Equus ferus caballus) population inhabiting Sable Island, Nova Scotia, Canada relies on forage from coastal maritime plant communities, including Beach Pea (Lathyrus japonicus). Horses have a strong sensitivity to lathyrogens compared with many other mammals, and symptoms of lathyrism (gait abnormalities, hernias, hoof malformation) are sometimes observed in Sable Island horses. However, it is unclear whether Beach Pea on Sable Island produces lathyrogens at sufficient concentrations to cause disease. Using liquid chromatography–mass spectrometry (LC-MS), we tested immature, mature, and senescent Sable Island Beach Pea samples for two of the most common lathyrogens: L-β-N-oxalyl-α,β-diaminopropionic acid (β-L-ODAP) and β-aminopropionitrile (BAPN). We detected only trace amounts of β-L-ODAP and no BAPN, causing us to conclude that lathyrogens are unlikely to be the cause of the physical abnormalities observed in Sable Island horses. These results from an iconic Canadian ecosystem provide useful toxicological data for a common coastal maritime plant.