FARGO, N.D. — For many farmers and ranchers, the weather has been challenging for obtaining animal feed.
“Whether dealing with drought and/or excessive moisture, both can impact livestock feed with the development of molds,” cautions Yuri Montanholi, North Dakota State University Extension beef cattle specialist. “Molds are generally in the agricultural environment all of the time. The problem occurs when molds invade developing plants or stored feeds and grow under stress, producing mycotoxins.”
Not all molds are bad. Some are not toxin producers, but filamentous mold can reduce the nutritional value of the feed. Also, mold spores in feeds that are agitated, for example when feeding hay, can be irritating to the respiratory system.
The toxins usually are consumed in feed or possibly inhaled to cause harm. Often, the problem is a long-term one and cattle eat the suspect feed before producers realize they have a problem.
You can’t judge a mold toxin problem by the color of the mold, according to Michelle Mostrom, NDSU veterinary toxicologist. Certain molds such as Aspergillus spp. and Penicillium spp. are green, Alternaria spp. and Cladosporium spp. are black, and Fusarium spp., Diploidia spp. and some Penicillium spp. can be white. But mold growth does not always mean that toxins were produced. Also, molds can grow and die, and not be visually detected, yet they may have produced toxins that are in the feed.
Montanholi and Mostrom urge producers to be aware of feed conditions for livestock, particularly this winter. If molds are present in livestock feeds, the best approach is to discard the moldy portions of the feed and feed what appears to be normal. Although this may not completely avoid problems because the mold may be gone, but the mycotoxins remain in the feedstuff.
“As a veterinary toxicologist, I would say to be proactive and test a feedstuff that appears to be moldy for mycotoxins before feeding to animals, particularly pregnant animals,” Mostrom advises.
“Try to collect a representative sample of the feed,” she adds. “The best 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.”
If the feed is positive for mycotoxins, certain animals may not be affected by that particular contamination level or may be capable of metabolizing the mycotoxin. Under some situations, the mycotoxin feed can be diluted to a safe level in the final ration.
“This is a great opportunity for producers to minimize issues with mycotoxins while saving feed,” Montanholi says. “The exception is aflatoxin-contaminated feed, which is potentially carcinogenic.”
Different mold toxins can cause a variety of clinical signs in different species. An initial clinical sign of toxic feed can be feed refusal, poor weight gain and diarrhea. With continual mycotoxin exposure or exposure to high doses of toxins, damage can occur to the animal’s liver, kidneys, brain, fetus and other organs.
You cannot test for all mycotoxins and call a feed “safe,” Mostrom says.
“Scientists have discovered that these molds can produce hundreds to thousands of mycotoxins, and we do not know how all of the toxins affect animals and do not have standards or tests for all toxins,” she notes. “Laboratories can test for the more common mycotoxins that are known to cause harm in animals and provide some guidance for feeding contaminated feeds. This is certainly a good start to minimize problems with mycotoxins.”
Contact your county’s Extension agent or an NDSU Extension specialist to learn more about sampling for mycotoxin analysis, as well as for other feed analysis related to quality.
Many countries, including the U.S., have regulatory limits or advisory guidelines on contamination of mycotoxins in human and animal feeds. These mycotoxin limits in food/feed can vary significantly with susceptible species, age of the animal and production status. The mycotoxin guidelines are available on the Food and Drug Administration (FDA) website, or go the National Grain and Feed Association website () and look up FDA Guidance on Mycotoxins, or contact your local veterinarian or the NDSU Veterinary Diagnostic Lab.
— NDSU Agriculture Communication
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