Two researchers in the Michigan State University College of Agriculture and Natural Resources are examining whether Bt corn, a type of genetically modified corn known for its ability to fend off pests, has benefits beyond those already known. It could possibly have benefits for the safety of human food and animal feed.
Felicia Wu and David A. Hennessy have been awarded a three-year, $478,000 grant from the USDA National Institute of Food and Agriculture for a project investigating Bt corn’s potential ability to reduce aflatoxin, a toxin produced by corn mold that can have significant negative health impacts on the liver, including cancer and acute failure. Wu is a John A. Hannah distinguished professor in the MSU departments of Food Science and Human Nutrition (FSHN) and Agricultural, Food and Resource Economics (AFRE), and Hennessy is an AFRE professor and Elton R. Smith chair in food and agricultural policy.
Gary Munkvold, a professor in Iowa State University’s Department of Plant Pathology and Microbiology, is also part of the project. Jina Yu, a former doctoral student under Wu, aided with the preliminary research on Bt corn and aflatoxin that led to the grant award. Yu is now a professor at Beijing Normal University in Beijing.
“We haven’t really known whether there is an impact of Bt corn in reducing aflatoxin, and previous field studies have not really come to a strong conclusion one way or the other,” Wu says.
Study to use crop insurance claims
To examine the potential impact of Bt corn on reducing aflatoxin, Wu and Hennessy will review aflatoxin-related crop insurance claims filed by corn growers using existing data from the USDA Risk Management Agency. While analyzing this data, they will search to see if there are fewer aflatoxin-related insurance claims where Bt corn is planted.
“If we do find that Bt corn has these impacts of reducing aflatoxin, even controlling for climate variables and grower practices, then we can say, ‘There’s this benefit of Bt corn that typically doesn't enter policy decision-making,’” Wu says.
Climate change may increase aflatoxin’s range
Aflatoxin is a mycotoxin, or a toxin produced by fungi. The fungi that produce aflatoxin, called Aspergillus fungi, typically thrive in warmer climates, like those of sub-Saharan Africa, South America and parts of Central America and Asia. Aflatoxin isn’t as common in the United States, but has a presence in Southern states. According to a previous study from Wu and collaborators from FSHN and Iowa State University, states such as Texas, Mississippi, Alabama and Georgia have the worst incidents of aflatoxin in corn.
Aflatoxin hasn’t been a major issue of concern for states in the Corn Belt, except in summers when there is a significant drought and unusually high temperatures. But that might not be the case in the future.
“As climate changes, that impact might move further north, to where most of the corn is produced,” Hennessy says.
Potential aflatoxin health risks
If that warming climate impact moves further north, so do potential health risks. There is a known positive correlation between aflatoxin levels and liver disease in both humans and animals. Although the U.S. Food and Drug Administration regulates aflatoxin in human food and animal feed, increased levels of aflatoxin in U.S. corn could mean that feed sold has aflatoxin levels closer to maximum tolerable limits.
Per the USDA, the standard maximum tolerable limit of aflatoxin in corn varies based on how it’s used:
• for human consumption, feed for dairy animals and immature animals, and when the destination is not known, 20 parts per billion (ppb)
• for breeding beef cattle, swine or mature poultry, 100 ppb
• for finishing swine 100 pounds or greater, 200 ppb
• for finishing beef cattle, 300 ppb
Bt corn's effect on aflatoxin
According to a previous study from Wu, aflatoxin has been shown to stunt animal growth, which could have impacts for producers who use corn in their animal feed. There may be some broader impacts, too, as corn is also a common ingredient in pet food.
“Thinking in terms of the livestock and poultry producers, having smaller animals and having sicker animals could have a detrimental impact, both on the actual animals and on the producer’s livelihood,” Wu says. “By improving the safety and quality of animal feed, we can achieve better livestock and poultry production.”
Wu has been studying Bt corn for 20 years, and she is eager to answer this question she has thought about since she studied another mycotoxin called fumonisin as a research intern for the U.S. EPA while in graduate school at Carnegie Mellon University.
“It was really exciting to work in policy; but at that time, we could not say that Bt corn reduced aflatoxin, because we didn't have the proof for it,” Wu says. “Now, almost 20 years later, this might be a way to answer that question more definitively.”