Aflatoxin in corn

Farmers in the midwest have had a rough go this year. Things started out looking pretty good this spring. The winter weather was mild and farmers were able to get into the fields and start planting earlier than usual.

And then there was no rain. Lots of crops suffered from lack of water. We did finally get some rain here in Indiana in August. That helped some of the crops that were planted later, but it was too late to save some fields.

And then it kept raining.

Don’t get me wrong, we’re still behind on overall moisture for the year. But it seemed that Mother Nature was trying to catch up with a lot of rain all at once.

While this might sound like a good thing, the extra rain late in the season has caused some problems of its own, especially with the field corn harvest.

In a “normal weather” year, the ears of corn will start to dry out while they are still on the plant. The weight of the dry ear will bend the dry stalk down so what was the top of the ear of corn all summer long is now pointing down at the ground. This helps keep moisture from getting down inside the protective shuck and into the kernels.

This year, the dry ears didn’t weigh quite as much. And the extra rains came before the ears were all pointing towards the ground. So water got inside the protective shuck around the corn cob and got to the kernels.

And the corn got moldy.

Aspergillus-infected corn, photo from Hoosier Ag Today

This might not sound like a big deal (other than being kind of gross). But moldy corn is a pretty big issue. One of the types of fungus that infects corn is called Aspergillus. This particular strain of Aspergillus produces something called aflatoxin inside the corn kernels. As the name might imply, aflatoxin is toxic to people and to animals. In animals it can cause everything from an upset stomach, to pregnancy loss, to seizures and death. In people, in large doses, it can cause cancer. Low levels of aflatoxin over a long period of time can cause immune suppression, making people and animals more susceptible to other diseases.

Every load (a big semi truck) of corn is tested for aflatoxin at the processor before it is bought from the farmer. If the level of aflatoxin in a load of corn is too high, the farmer can’t sell it. And just a couple of bad ears of corn can contaminate an entire load.

The FDA has set specific levels of aflatoxin that are acceptable for sale and use as feed. Corn that is destined for food for people must have less than 20 parts per billion (ppb) of aflatoxin. Corn for most animal feeds can have up to 300 ppb (some types of animal feeds are limited to 20 ppb).

(20 parts per billion is like having 10 million dollars in pennies – that’s one billion pennies! – and only 20 of those pennies are painted  bright blue. You would have 20 ppb of bright blue pennies.)

So in a year when farmers and ranchers already had a shortage of hay and corn to feed their animals, good-quality corn is going to be even harder to come by. Farmers can blend two batches of corn, one with higher aflatoxin and one with no aflatoxin, to end up with corn that has low enough aflatoxin to be able to feed. (Dilution is the solution to pollution, after all!) But farmers will still need to be very careful in deciding what to feed their animals over the winter.