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Cyanide Poisoning

Hydrocyanic Acid Toxicity, Prussic Acid Poisoning

Several different plants and plant parts (seeds from the fruit) have the potential to cause plant-related cyanide poisoning in poultry. These plants and plant parts contain varying amounts of cyanogenic glycosides, which when damaged, produce cyanide. Once consumed, cyanide is quickly absorbed from the gastrointestinal tract into the bird's bloodstream. Once in the blood it travels all over the body and inhibits blood cells from delivering oxygen to tissue cells. The blood becomes supersaturated with oxygen and appears bright red.

Factors that Increase Toxicity of Plants

The amount of cyanogenic glycosides found in plants varies depending on the plant part, season, stage of growth of the plant, whether herbicides were recently used, and environmental conditions.
Drought and frost or freezing are stressful conditions that increase the risk of high levels of cyanide accumulation in affected plants. Any stressful condition that inhibits the growth of the plant can cause higher amounts of cyanide to develop. New plant growth also has higher levels of cyanide then mature plants. Leaves of cyanide-accumulating forage grasses produce 25 times more cyanide than the stems.

Which Plants Contain Cyanide?

Plants capable of producing high levels of cyanide include:

Signs of Cyanide Poisoning

Chickens that die from cyanide poisoning have bright red, oxygenated blood and bodily tissues are usually congested with blood. The reported oral LD50 for domestic chickens is 11.1 mg/kg of body weight. Chickens will usually die within 15 to 30 minutes of ingestion of the toxic substance.

Clinical Signs

Rapid blinking
Blue-purple colored comb
Sudden death


  • History
  • Necropsy
  • Blood test


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 immediately.



Do not feed chicken foods or forages that contain cyanogenic glycosides or cyanide. This includes cherries, apricots, peaches, almonds, apple seeds, cassava root, etc.



Scientific References

Risk Factors

  • Feeding chickens large amounts of apples (containing seeds), apricots, peaches, almonds, cassava root or cherries