Aflatoxin, a cancer-causing agent that develops from fungi on corn, is a risk for farmers who feed corn-based rations this fall, said Mike Hutjens, University of Illinois Extension emeritus dairy nutritionist.

“Two weeks ago we dumped milk in Illinois,” he said at a Professional Dairy Producers of Wisconsin Feed & Nutrition Conference on Sept. 25. The milk’s aflatoxin levels were over the 0.5 part per billion (ppb) human- consumption limit set by the Food and Drug Administration, he added. The good news is that Hutjens and colleagues helped the dairy managers get back in business within 24 hours after introducing clay-based binders into the cows’ diet.

He advised producers to test aflatoxin levels and work to keep them below the maximum levels set for rations, including 20 ppb in lactating cattle;100 ppb in breeding beef, swine and dairy; 200 ppb for swine; and 300 ppb for beef steers.

“Cows excrete 1-2% of the aflatoxin in their milk, because it’s in the blood. And that varies from cow to cow,” Hutjens warned. If aflatoxin levels in rations are 20 ppb, that multiplied by the 2% excretion rate equals 0.4 ppb – nearly that 0.5 ppb rejection level.

He suggested that producers whose feeds may be at high aflatoxin levels have them tested to determine which are problematic. Dairy co-ops are actively monitoring for aflatoxin as well.

To keep aflatoxin levels in manageable ranges, dilute affected feeds with “wholesome” forages and grains, Hutjens said. Or add a clay-based binder, also called a flow agent. Ammoniating the corn grain, which breaks the ring structure of the aflatoxin, is another option. Also beware of similar risks from corn byproducts, such as distillers grains.

Don’t store aflatoxin-infected corn as high-moisture corn – dry it down to less than 14% moisture, the dairy nutritionist added. For more information, view our video: Beware The Risks Of Aflatoxin In Corn-Based Feeds.