Attention! This is a potentially life-threatening condition for your horse. Time is of the essence, contact your veterinarian immediately.Find a Vet


Aflatoxin Toxicosis, Aflatoxin Poisoning

Aflatoxicosis is a fungal toxicosis caused by eating feed contaminated with aflatoxins. Aflatoxins are a specific type of mycotoxin that are produced by two types of fungi, Aspergillus flavus and A. parasitus.
There are over 20 types of aflatoxins, although the four major types are designated as B1, B2, G1 and G2. Aflatoxin B1 is the most dangerous. Aflatoxins mainly cause damage to the horse's liver. Clinical signs that may or may not develop prior to death, are related to liver failure resulting from damage caused by aflatoxins.

Clinical signs of Aflatoxicosis

Horses may develop acute or chronic aflatoxicosis, depending on the amount of the toxin they've eaten. Horses that develop acute aflatoxicosis usually won't show any clinical signs other than sudden death. In chronic cases, which are the most common, clinical signs include loss of appetite, weakness, depression, anemia, jaundice (yellowing of mucous membranes), weight loss, and eventually death from liver failure.

Risk of Feed Contamination

The fungi which produce the toxins grow on carbohydrate rich feeds such as peanuts, cottonseed, corn, sorghum and cereal grains when they are stored in warm (78-90°F (25.5-32°C)), humid (relative humidity of 97-99%) conditions. Peanuts and corn can be contaminated before harvest, when drought leads to premature drying of the developing seeds.


Jaundice (yellowing of mucous membranes)
Loss of appetite
Brown urine
Poor haircoat
Increased heart rate
Increased respiratory rate
Rapid weight loss
Sudden death


  • History
  • Clinical signs
  • Blood testing - for anemia, elevated liver enzymes, serum bile acids, albumin:globulin ratio; prothrombin activity
  • Mycotoxin testing of feed

While waiting for your veterinarian

  • Remove suspected feed source from horse access



Supportive careFor resulting liver damage
Supplemental vitaminsL-methionine and Vitamin E


Scientific Research

General Overviews

Risk Factors

  • Improperly storing horse feed. Leaving it exposed to warm temperatures and moisture.