Nearly half of the commercial feed samples German researchers analyzed had pyrrolizidine alkaloid levels that were higher than the accepted maximum tolerated levels, and the highest rates occurred in alfalfa- or herb-based feeds. | Photo: Anne M. Eberhardt/The Horse

Nearly half of the commercial feed samples German researchers analyzed had pyrrolizidine alkaloid levels that were higher than the accepted maximum tolerated levels. The highest rates occurred in alfalfa- or herb-based feeds, said Ingrid Vervuert, DrMedVet, of the University of Leipzig Faculty of Veterinary Medicine, in Germany.

Also present in some kinds of honey and tea, pyrrolizidine alkaloids—naturally occurring organic compounds—can cause liver dysfunction in a variety of species, including humans and rats, Vervuert said. Their effects on horses, however, haven’t been studied in detail.

“More research is necessary, but we expect the feed companies to become more self-controlling (with regard to the management of their product), as there is a potential risk of pyrrolizidine alkaloid contamination, especially in herb-containing commercial feeds,” she said