Should farmers test feed?

Gloria Hafemeister

Fond du Lac — The rainy period that hit this year just as farmers were trying to harvest their corn silage has created an environment where molds and funguses may be present.

With many dairies feeding high forage diets with a lot of corn silage and processed kernels in it, there is a concern about the possibility of mycotoxins due to the wet harvest season this year.

The concern with molds is their ability to produce poisons known as mycotoxins that impact animal performance

Tina Kohlman, Fond du Lac County UW-Extension dairy and livestock agent, said just because there is mold on the corn silage does not mean mycotoxins are present, but she also noted mycotoxins can be present even when there is no visible mold, and that’s a greater worry.

She told dairy producers attending the dairy forage field day in Fond du Lac to work with their dairy nutritionists and agronomists to closely evaluate both corn silage and corn for grain for mycotoxin levels.

“Mycotoxins are impossible to detect without testing,” Kohlman cautioned.  “Anything above freezing temperatures will allow the growth of it on corn silage, and processed kernels are the perfect product for producing mycotoxins.”

Warm conditions this fall could have accelerated the rates of spoilage and mycotoxin accumulation. If mycotoxins were present in the field at harvest, they will remain present in storage at similar concentrations.

Many crops can be susceptible to mycotoxins, but on a dairy farm it is mostly the corn silage, Kohlman said. With dairy farms that utilize high forage diets for their animals who consume a lot of feed, this can be the greatest concern.

She shared research provided by John Goeser of Rock River Lab at Watertown. Tests done there indicate that this year there are more samples showing issues with the toxins on samples from farms in the Midwest than from eastern states.

There are different types of toxins to be concerned about.

Aflatoxin contamination is the only one that is FDA regulated. If it is present, the feed should be discarded because it can get into the milk.

Other mycotoxins are also a concern. Vomitoxin is considered a marker. If it is present, there are likely other toxins present as well.

Mycotoxins affect cows in different ways. They affect the rumen and the metabolizing of feed, and some will suppress the immune system.

Chronic levels can lead to reduced feed intake, altered rumen fermentation and digestive upset, diarrhea, intestinal irritation, lethargy, reduced milk production and lowered reproductive rates. Mycotoxins can also suppress immunity, making cattle more vulnerable to disease.

Kohlman suggested testing feed if there is any suspicion of a problem.

As for management of mycotoxins, she noted that best management practices at the time of harvest can help, but make sure best management practices are also used at the time of feed-out.

If mycotoxins are found to be present, dilution is one solution. There are also binders available or the feed could be given to less susceptible animals on the farm rather than lactating cows.

It is also helpful to reduce stress in the herd, both environmental and nutritional, and maintain the cow’s rumen pH.  Protein and energy levels should be at NRC recommendation levels or higher to support the immune system. Feeding vitamin E or antioxidants may also be helpful.

Kohlman suggested working with the nutritionist when there are concerns about whether it is present. Besides Rock River Lab, several other laboratories do mycotoxin testing, including AgSource and Dairyland.