Caution to horse owners about toxic natural products in feed

Among the many duties charged to the US FDA is the safety of veterinary feed. Therefore, equestrian enthusiasts should take note of the following warning from the FDA Center for Veterinary Medicine on natural contamination of certain corn products with a toxin produced by an endophytic fungus of the Fusarium genus:

FDA Warns Horse Owners About Fumonisins in Horse Feed

Each year, a number of horses die from eating corn or corn byproducts containing fumonisins. Fumonisins are a group of toxins produced by an endophytic mold found within the corn kernel. Typically, fumonisins are produced while the corn plant is growing in the field, but levels can also increase under improper storage conditions after harvest.

Although more than ten types of fumonisins have been isolated and characterized, the most prevalent in contaminated corn is fumonisin B1 (FB1), which is believed to be the most toxic. The dangers from fumonisins are dose-related, and horses and rabbits are the most susceptible of the domestic species.

Fumonisins can produce the serious neurological disease known as leukoencephalomalacia in horses. Most of the investigated cases of fumonisin poisoning in horses have involved corn screenings. For this reason, FDA recommends that corn screenings NOT be used in horse feed. Corn and feed containing corn also needs to be kept dry and protected from moisture when stored to prevent levels of fumonisins and other mold toxins from increasing. FDA recommends that corn and corn by-products used in horse feed should contain less than 5 parts per million (ppm) of fumonisins and comprise no more than 20 percent of the dry weight of the total ration.

In November 2001, CVM and FDA's Center for Food Safety and Applied Nutrition jointly issued a final guidance for industry on fumonisin levels in human food and animal feeds, which can be viewed at: http://www.cfsan.fda.gov/~dms/fumongu2.html Additional information about fumonisins is also available at: http://www.fda.gov/cvm/fumonisin.htm.

Researchers at Ohio State University have a handy web reference of fungal toxins in food, often referred to as mycotoxins.

Fumonisin B1 has an unusual mechanism of action discovered in 1991 that led to its use as a tool in investigating sphingolipid metabolism. Its ability to inhibit the enzyme, ceramide synthase, activates the tumor necrosis factor-alpha (TNF-alpha) pathway, leading to cell death in the liver, kidney, and brain. Perhaps we can talk our ScienceBlogs colleague, Molecule of the Day, into discussing the chemistry of this class of mycotoxins.

This episode serves as a general reminder well-known to Terra Sig readers that nature is full of both cures and poisons...so be careful out there.