by Courtney Llewellyn

Aflatoxins are a family of three toxins produced by certain fungi that are found on agricultural crops such as corn, peanuts, cottonseed and tree nuts – and when cows consume contaminated feed, the toxins can severely affect their livers and be excreted in their milk. Farmers try to prevent their herds from eating anything that could cause this issue, and it turns out feeding them something else may help more than previously thought.

Dairy producers can use clay supplements in cows’ diets to reduce the transference of aflatoxin into milk, but a new study revealed that clay has additional benefits for overall cow health.

According to a release from the University of Illinois, researchers noted that there has already been a lot of research done showing the effects of clay supplements on milk quality and performance. “We took it a step further to look at how clay can help the cow’s immune system,” Russell Pate, a doctoral student in the Department of Animal Sciences at the university, explained.

When used as part of a cow’s diet, clay binds to aflatoxin, which prevents it from being absorbed by the cow’s bloodstream. The toxin is then excreted through feces. In their study, the researchers gave a group of cows four ounces of clay in their total mixed ration and another group eight ounces, to see if more clay would make a bigger difference. The results: cows given eight ounces of clay in their daily rations produced more milk with less aflatoxin. That’s nothing new, though. Other studies have had similar results. What was new with this study was how the clay supplements affected the cows’ overall health.

“By minimizing the amount of aflatoxin getting into the cow’s bloodstream through the clay supplements, we wondered if that would help the cow’s immune system stay stronger, in a sense. That hadn’t been tested as much,” Pate explained.

Phil Cardoso, an assistant professor in the Department of Animal Sciences at the university, noted that cows fed the eight ounces of clay a day had substantially less liver inflammation caused by aflatoxin. Additionally, indicators of liver functionality and immune response tended to increase in the liver and the blood as the clay concentration in the cows’ diets increased.

“If you add clay to the diet, you will have a decrease in aflatoxin getting to the milk and will potentially be bolstering the immune system as well,” Pate said.

“I don’t think simply using a straight clay supplement to dairy rations is very common to control aflatoxins (or other mycotoxins),” said Gabe Middleton, DVM, president of the Council for Agricultural Science and Technology. “You would need to add around 0.5 pounds/cow/day to achieve desired results. Most nutritionists do not want to add that much clay to a ration due to potential palatability issues.”

Clay is more commonly added to combination products that have an ingredient list such as clay, specific binding bacteria and direct fed microbials, according to Middleton. “An example of such a product is Select DTXm,” he said. “There are other binder products that also work well to bind aflatoxins (and other more common toxins such as vomitoxin and zearalonone). Those products may contain ingredients such as beta-glucans that bind the toxins in the GI tract. An example of such a product is Celmanax from Arm & Hammer.”

Adding clay deals with a problem after it’s been identified; what can be done to stop the toxins from entering the diet in the first place? Virginia Ishler, Extension dairy specialist with Penn State, listed the following steps for best management practices at harvest, storage and feed out to decrease the potential effects of toxins: Store silage and grain at the proper moisture content for the storage structure; if mold is obvious or conditions are right for toxin development, utilize a suitable silage or grain additive; use laboratory testing to confirm contamination if it is suspected; evaluate all aspects of feeding management and nutrition to confirm they are not the culprit for poor animal performance; and finally consider feed additives – like clay – along with diluting the contaminated feed in the ration.