Horse Care And Health

Aflatoxin Poisoning in Horses

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Aflatoxin is a potent toxin that thrives in wet, humid conditions and can be present in pasture grass, hay and concentrate feeds, although it is most likely to be found in corn. This chemical, formed by the mold aspergillus, is among one of the most poisonous naturally-occurring substances known to exist. Once ingested, the aflatoxin attacks the liver, causing cell necrosis and interfering with protein synthesis. Horses suffering from aflatoxin poisoning exhibit a variety of symptoms, and the condition may be difficult to diagnose.

Signs and Symptoms

Aflatoxin poisoning is uncommon in horses, and its symptoms can easily be mistaken for other serious conditions. Acute aflaxin poisoning occurs when the horse ingests large quantities of the toxin at once. Symptoms include severe depression, lack of appetite, fever, colic or abdominal pain, loss of coordination and frequent lying down. Manure and urine may be bloody.  Muscle spasms and convulsion may occur, and in the most extreme cases, death.  

Chronic aflatoxin poisoning can happen when the horse ingests small quantities of the toxin over a longer period of time. In the event of chronic poisoning, the horse's immune system is weakened and he may be prone to frequent infections or disease. The horse's coat might appear dull or rough and he may lose weight rapidly. Hematomas may be present beneath the skin. Horses may exhibit poor appetite, depression, fever and jaundice of the mucous membranes. Muscle spasms, respiratory problems and neurological disorders can also result from aflatoxin poisoning. The toxin interferes with reproductive health and reduces the growth rate of young horses.


Diagnosing aflatoxin poisoning can be challenging. Blood work will likely show elevated liver enzymes as well as other abnormalities that are non-specific. Should the veterinarian suspect aflatoxin poisoning, a sample of the horse's feed can be tested for the chemical. If the horse has ingested aflatoxin, an orally administered treatment of activated charcoal may be used to clear his system of the poison. The charcoal will absorb the toxin, allowing the horse's body to excrete it. Vitamin supplements can help rebuild a horse's immune system. The veterinarian may prescribe a diet low in fat that is easy for the horse to digest.  


The factors that affect an animal's response to aflatoxin poisoning include age, workload, stress level and adequacy of diet. The state of a horse's immune system can determine recovery time. Horses who have been affected by aflatoxin will develop a sensitivity to it, and may have a strong reaction if exposed to it again.

Aflatoxin poisoning can be prevented with a thorough inspection of hay and grain. The horse's forage and bedding should also be free of mold. Pastures can be mowed to keep grass from developing seed heads, which encourage the development and airborne spread of aflatoxins. Storing hay and grain in a dry, covered area free of moisture will protect the horse's food supply. 

More about this author: Joanna Ehlers

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