Fumonisins (FUM) are produced by the secondary metabolism of several toxigenic fungi of the Fusarium and Alternaria genera, particularly F. verticillioides. There are about two dozen known FUM, B1 and B2 being the most toxic.

FUM occur especially in corn, at concentrations that induce subclinical intoxication in different species. Horses are highly sensitive, and show clinical signs of harm to the nervous system, thus characterizing Equine Leucoencephalomalacea. Pigs are also sensitive and may present with pulmonary edema, dyspnea and cyanosis. Chronic intoxications are more frequent and reduce productivity.

Birds are more resistant to the effects of FUM. When challenged with moderate and constant doses of these toxins in the diet, they may experience a decline in performance and an increase in the size of internal organs.

Clinical signs caused by FUM and species sensitivity: