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Acorn Toxicosis

Oak Poisoning, Tannin Toxicosis

Acorn toxicosis occurs in many animal species, caused by ingestion of hydrolyzable tannins contained within oak twigs, buds, leaves and acorns. There are over 500 different species of oak (Quercus spp) trees worldwide, with 70 of them found in North America. All species are considered to be toxic to animals. Oaks are classified into multiple groups according to their leaf color--red, black and white oaks. Black and red oak species have been reported to contain higher amounts of tannins then others.

Green acorns and budding leaves contain the highest levels of tannins, which is why most cases of poisoning in animals occur in the spring and fall. Fallen acorns will remain toxic for several months after falling from trees. Tannins have protein-binding properties, and are known to inhibit several digestive enzymes, including proteases, pectinases, amylases, cellulases, and lipases. When ingested by ducks, the tannins, as well as their metabolites, can cause severe gastrointestinal damage, kidney dysfunction, and possibly mechanical obstruction.

Most of the time, signs of poisoning occur several days following when oak parts were first eaten by ducks. If diagnosis and treatment are delayed, it often leads to severe kidney and liver damage which can be fatal. The only treatment for ducks with suspected acorn toxicosis is prompt recognition of the problem, supportive care, and diuresis to aid in clearing the toxins from the duck's system.

Ducks don't normally have a preference for eating acorns, and if they are well fed acorn toxicity is generally not a problem. However, sometimes there is an occasional duck that likes acorns, and will actively seek them out to eat. Some ducks can eat acorns without any problems, however others develop signs of poisoning.


Regurgitating food
Loss of appetite
Pale mucus membranes
Excessively increased urine output
Increased thirst
Absence of fecal output


  • History
  • Clinical signs
  • Physical exam
  • Complete blood count (CBC)
  • Plasma biochemical profile
  • Radiography
  • Endoscopy


MethodMethod Summary
Supportive careCrystalloid fluid therapy (Normosol-R with 2.5% dextrose), including 5% amino acids and 2 mL of vitamin B complex administered at a rate of 60 mL/kg/d as mixed in a 1-L bag
Whole blood transfusionMay be needed in severe cases of anemia
Nonsteroidal anti-inflammatoryMeloxicam (0.2 mg/kg SC q24h)
AntibioticEnrofloxacin (10 mg/kg IM q12h)
Supplemental nutrients50



Risk Factors

  • Keeping ducks confined in an area underneath oak trees
  • Malnourished or starving ducks, with little to no alternative food source