Pyrrolizidine alkaloids of European Senecio/Jacobaea species in forage and their carry-over to milk: A review

Species of the genera Senecio and Jacobaea, particularly tansy ragwort (Jacobaea vulgaris, syn. S. jacobaea) and marsh ragwort (J. aquatica, syn. S. aquaticus) have spread as weeds in Western and Central Europe in poorly managed pastures and meadows during the last decades. Due to high level of numerous toxic pyrrolizidine alkaloids and their N-oxides (PAs) in contaminated forage they present a threat for livestock. Horses are of the greatest risk, while ruminants are more resistant due to a partial detoxification in the rumen. The susceptibility decreases in order cattle, goats and sheep. The risk during grazing is limited because animals mostly avoid the unpalatable weeds. During feeding stabled animals with cut fresh forage, hay or silage the risk however lasts. Haymaking preserves the PAs, whereas ensiling partly decreases their level. The carry-over to milk is dose-related and seems to be low. Even the observed low PA levels in cow milk may be of concern for human health as regards hepatotoxic and genotoxic properties. Recent data on PAs chemistry, toxicity, factors affecting their content, composition and distribution within the Senecio/Jacobaea plants, changes in silage and hay and carry-over to milk are reviewed.

Automated summary

Species of Senecio and Jacobaea genera, such as tansy ragwort and marsh ragwort, have become weeds in Western and Central Europe. These plants contain toxic pyrrolizidine alkaloids that pose a threat to livestock, particularly horses. Ruminants are more resistant due to partial detoxification in the rumen, but there is still concern about carry-over of these toxins into milk.