Fumonisins are structurally similar to sphingolipids, which are lipids commonly found in neural tissue and play key roles in cell recognition and signal transmission. This group of mycotoxins is primarily produced by F. verticillioides F. proliferatum and eleven other Fusarium species. Fumonisins are generally considered to be the cause of “moldy corn poisoning” in horses, mules, and donkeys. This disease in horses is known as equine leukoencephalomalacia. Fumonisins also cause liver disease in horses and have cardiac effects, cause pulmonary edema of swine, and are strongly associated with esophageal cancer and neural tube defects of humans. Leukoencephalomalacia typically occurs in horses, mules, or donkeys foraging corn left standing in the field after harvest, or fed grain screenings heavily infected with F. verticilloides. The toxins fumonisin B1 and B2 are produced only by certain strains of F. verticillioides. This toxicant is also carcinogenic in laboratory animals. Dietary levels of ~10 ppm of fumonisins in feed caused leukoencephalomalacia in horses after 30 days. Dietary levels of >100 ppm fumonisins caused pulmonary edema in swine to occur within 4 days. F. verticillioides is common even in food-grade corn and is often abundant in ground feeds and in silage particularly when corn is produced under drought conditions and where insect (e.g. European Corn Borer, Corn Earworm) damage to ears is common. Corn infected with F. verticillioides is very friable and thus easily broken, therefore horse owners should avoid feeding screenings to horses. Research on the fumonisin toxins began only recently and current thought is that concentrations of >5 ppm in corn or 1 ppm in the final ration are necessary for mycotoxicosis in horses and >10 to 20 ppm for swine. The U.S. Food and Drug Administration has proposed advisory guidelines (Table 2). As with other toxigenic fungi, various strains of F. verticillioides vary greatly in their ability to produce mycotoxins .
Table 2. Regulatory limits for mycotoxins in the USA.
|
Mycotoxin |
Regulatory limit |
|
Aflatoxin B1,B2, G1, G2 |
20 ppb for all products for human food, immature animals and dairy cattle, animal feeds other than corn or cottonseed and grain for export 100 ppb for corn and peanut products intended for breeding beef cattle, breeding swine or mature poultry 200 ppb for corn and peanut products intended for finishing swine of 100 lbs. or greater 300 ppb for corn and peanut products intended for finishing beef cattle or cottonseed meal intended for beef cattle, swine or poultry
|
|
Aflatoxin M1 |
0.5 ppb for milk |
|
DON |
1 ppm for all finished wheat products, e.g. flour, bran and germ that may be consumed by humans 10 ppm for all grains or by-products destined for beef cattle older than 4 months and for chickens; these ingredients should not exceed 50% of the diet 5 ppm all grain or by-products destined for swine; these ingredients should not exceed 20% of the diet 5 ppm all grains and by-products for all other animals; these ingredients should not exceed 40% of the diet
|
|
Fumonisins total of B1, B2 and B3 (proposed regulations-FDA, 2000) |
2-4 ppm Human foods 5 ppm (<20% of diet)Horses and other equids and rabbits 20 ppm (<50% of diet) swine and catfish 30 ppm (<50% of diet) breeding ruminants, poultry, mink, dairy cattle, laying hens 60 ppm (<50% of diet) ruminants>3 months before slaughter and mink for pelt products 100 ppm (<50% of diet) poultry raised for slaughter 10 ppm (<50% of diet) all other species or classes of livestock and pet animals |
|
Ochratoxin A |
No regulation in the USA but the European Union has a 250 ppb guidance value for corn based animal feeds, 5 ppb for raw grains destined for human products, 3ppb for all grains and cereal products destined for human consumption and 10 ppb for dried vine fruits |
|
Zearalenone |
No regulation in the USA but 1 ppm is advised. |
|
Other mycotoxins |
No regulation in the USA |
Date: 11/11/2007
