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Mycotoxins

From the February 2020 Newsletter:

Mycotoxins are detected frequently in feed submitted to the toxicology lab. The 2019 Dakota weather often was challenging: either too wet or too dry, cool to frigid temperatures, and an early autumn snowfall. Some of last year’s corn harvest submitted to the toxicology lab revealed tortuous growth and mold invasion of corn and the cob (Figure 1A).

Typically, the lab detected mycotoxins produced by Fusarium spp. (Figure 1B) and some Penicillium spp. Black mold growing on corn indicated possible Alternaria or Cladosporium, with the latter mold not a recognized mycotoxin producer.

Mold growth does not always mean toxin production. However, 2019 laboratory analyses often found multiple Fusarium mycotoxins: DON (deoxynivalenol or vomitoxin), zearalenone, fumonisins and, occasionally, the more toxic T-2 and H-T2 toxins. Submitted corn has been wet (stored wet or piled in wet/cool conditions), which promotes mold growth and, subsequently, mycotoxin production. If 2019 is like 2009, the corn left in the field eventually can dry and be less likely to have mold/mycotoxin issues.

When molds are present in livestock feeds, the best approach is to discard the moldy portions of the feed and use what appears normal as animal feed. The lab urges livestock producers to be proactive and test feedstuff that appears to be moldy for mycotoxins before feeding to animals, particularly pregnant animals.

Try to collect a representative sample of the feed. The best method is to collect multiple samples of grain while transporting the feed from the field to bins or to a truck, or collect multiple samples of hay (e.g., probe) or silage during feeding.

Ruminants on an adequate ration often have rumen microflora that metabolize some of these mycotoxins to less toxic compounds. Different mold toxins can cause a variety of clinical signs in different species.

Initial clinical signs of toxic feed can be feed refusal, poor weight gain and possible diarrhea. With continual mycotoxin exposure or high-dose exposure to toxins, damage can occur to the animal’s liver, kidneys, brain, fetus and other organs.

The NDSU-VDL can test for the more common mycotoxins in feed that are known to cause harm in animals and provide some guidance for feeding contaminated feeds. We recommend using a testing laboratory that is not also in the business of selling “mycotoxin binders,” which could be a conflict of interest. The U.S. Food and Drug Administration (FDA) has regulatory limits or advisory guidelines on contamination of several mycotoxins in human and animal feeds. These mycotoxin limits in food/feed can vary significantly with susceptible species, age of animal and production status. The mycotoxin guidelines are available on the FDA website or the National Grain and Feed Association website (www.ngfa.org), or by contacting the NDSU-VDL Toxicology section.

Figure 1: (A) Moldy, tortuous corn cobs submitted to the lab from the 2019 harvest; (B) Fusarium spp. invasion exhibited by the pink mold on the corn husk (upper right) and white fungal hyphae growing on the corn kernels. (Dr. Michelle Mostrom, NDSU).