Pyrrolizidine alkaloid (PA) toxicity occurs in chickens as a result of eating plants containing pyrrolizidine alkaloids. It can be an acute poisoning if large enough quantities are eaten, however it is most often the result of a chronic poisoning, where clinical signs may take weeks to months following consumption of a sufficient quantity of the toxic plant. Toxicity is cumulative, over the course of a chicken's lifetime.
PA toxicity causes liver disease. Chickens with liver disease may not initially show any clinical signs, or the symptoms can appear very vague and often are confused or mistaken for other diseases. Toxicity occurs in chickens of all ages and breeds, but not all members of the flock will develop signs of liver damage.
PAs belong to a class of phytotoxins which are present in more than 6000 plant species. Some of the most commonly known causes of poisoning cases in chickens and other farm animals include: