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Pyrrolizidine Alkaloid Toxicity

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:

Clinical Signs

Loss of appetite
Neurologic behavior abnormalities
Excessive drinking


  • History
  • Clinical signs
  • Physical exam
  • Low plasma or serum zinc levels


Supportive care: Isolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.



Learn how to identify what plants contain PAs, and regularly inspect the premises for their presence



Scientific References

Risk Factors

  • Overgrowth of PA-containing plants in fields where chickens are kept, as they are often considered to be common weeds in many parts of the World.
  • If feeding your flock dried herbs, ensure they are purchased from reputable companies which practice quality control testing on their products, especially when involving comfrey.