Pyrrolizidine alkaloid-containing toxic plants (Senecio

Many problematic pyrrolizidine alkaloid (PA)-containing plants are foreign invasive weeds that invade pastures, fields, and ranges, and contaminate feeds and food. Others are native plants that may increase or expand on field edges or in disturbed areas. Most are unpalatable, only becoming a problem for livestock when alternative forages are unavailable, or when they are included in hay and other harvested feeds. Human poisoning is most often a result of contaminated grain or flour, although several poisonings have resulted from the use of PA-containing herbal preparations. Major PA plants and their specific health-related characteristics are discussed individually. INDIVIDUAL PYRROLIZIDINE PLANTS Senecio Specie