Immediate drying, bin aeration can minimize effects of mycotoxins in corn

Aflatoxin contamination of corn is being reported in southeast, northeast, and west central Nebraska. Aflatoxin is one of several potentially harmful compounds known as mycotoxins which can develop from grain molds. While molds may not necessarily pose a health threat to animals or humans, mycotoxins can.

The level of aflatoxin contamination being reported ranges from 20 ppb to 300 ppb. The vast majority appear to be on the lower end from under 20 ppb to 100 ppb, according to Rich Reiman with the Nebraska Department of Agriculture.

Kansas also is reporting increased problems with aflatoxin this year.

In several Nebraska counties fumonisin contamination of food grade corn was a problem in 2001. This may be even more widespread in 2002.

The widespread drought stress during the growing season and the late season rains provided conditions which were nearly ideal for the development of grain mold and subsequent mycotoxin synthesis in corn. The presence of mold does not necessrily indicate contamination of the grain with mycotoxins. Only certain strains of certain species produce these potentially harmful compounds.

The impact of any mycotoxin contamination depends on the intended use of the grain. The FDA tolerances for aflatoxin are:

In many cases the levels being found exceed the FDA minimums for milk and dairy use. The FDA tolerances for fumonisins are much lower: 5 ppm for horses, 10 ppm for swine, and 50 ppm for cattle.

Most grain mold pathogens become associated with the kernel in the field, but they also can grow within the colonized kernel and even spread to adjacent kernels during storage. Consequently, it is imperative to dry down grain as soon as possible. Delaying harvest to let the grain dry in the field increases the risk of stalk rots and grain molds. In some cases it may be better to harvest at higher grain moisture and dry the grain rapidly. No fungicides are labeled in Nebraska for managing molds or mycotoxins of corn postharvest.

While it's always important to monitor stored grain throughout the winter, this year it may be critical to to keep an even closer eye on moisture content, especially in areas where mold and mycotoxin contamination have been common. It also will be important to keep the grain well aerated.

Grain with mold symptoms should be assayed for the presence of mycotoxins prior to use as food or feed. If mycotoxins are confirmed, producers may have several options, depending on the contamination level.

Elevators in some parts of Nebraska that buy corn for both human and animal consumption are reported to have turned away grain with mycotoxin levels above 20 ppb. While some elevators may not want to risk accidental contamination of food grade corn, the contaminated grain could still be marketed to a number of other outlets, depending on the level of contamination. These might include feedlots or elevators which only buy grain for feeding cattle.

Some grain elevators use the black light test as a preliminary indication of potential toxin contamination; however, this test is very unreliable. Many things will fluoresce under a black light, including insect parts and fungi that don't produce toxins. Consequently, many false positives can result. Only certain laboratory analyses can establish the occurrence and concentration of mycotoxins.

Mycotoxins can be toxic to farm animals, wildlife, or humans. Effects on animals include feed refusal, short-term illness, reproductive dysfunction, and death. Human effects include suppression of the immune system, reproductive dysfunction, cancer, and death. The ultimate effects depend on duration and concentration of exposure.

Most mycotoxins are extremely stable molecules and can withstand drying processes as well as many industrial processes. Consequently, exposure can result from not only direct consumption of contaminated grain but also from consumption of processed grain and industrial byproducts such as from industrial ethanol production.

Because molds or mycotoxins can develop in stored grain, remember to exercise caution and wear a dust mask to minimize exposure. In addition to mycotoxin concerns, exposure to the spores of the grain mold fungi can lead to acute allergic responses or chronic allergic responses. Clean trucks and bins which held contaminated grain.