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Molds and Mycotoxins in Dairy Feeds

25 January 2013

Immune suppression, liver damage and even cancer can be caused by substandard feed caused by corn put under stress through adverse weather, according to researchers at South Dakota University.

In the aftermath of the 2012 drought, a pressing issue facing dairy producers is the consumption of mold and mycotoxins in drought-stressed forages. Consumption of these contaminated feeds can lower herd performance, increase sickness, and sometimes result in death. But there are a number of ways that producers can recognize and manage the problem before it becomes fatal.

Dr. Lon Whitlow, professor emeritus at North Carolina State University, is featured in a recent SDSU Extension podcast discussing strategies for managing and preventing mold and mycotoxin poisoning in dairy cattle.  While the symptoms of poisoning are not always apparent, protecting your cattle starts by keeping a close eye on your supplies.

“A common toxigenic mold affecting drought-stressed corn in the Midwest is Aspergillus, which produces aflatoxin,” said Whitlow. The first signs of Aspergillus contamination in corn typically show as a brown-green, moss-like mold spread throughout the cob area of the corn.  Once ingested, the aflatoxin produced by Aspergillus can lead to mycosis, a dangerous condition under which the mold becomes an infectious agent, causing disease.

Left untreated, mycosis can slowly eat away at an animal’s interior, resulting in liver damage, hemorrhages, immune suppression, cancer, and even death. While the symptoms of mycosis are not always easy to recognize, a good first step to managing the disease is to test the aflatoxin levels of your feed supplies.

With Aspergillus being a common mold, it is not uncommon for corn feed supplies to contain at least trace amounts of aflatoxin, especially in drought conditions under which the mold flourishes. The current legal limit of aflatoxin in feedstuffs rests at 20 ppb (parts per billion), and this level can be tested for in a certified feed lab. “As long as you keep the level of aflatoxin below the legal limit (20 ppb), there will be no adverse affects on milk production or the health of your dairy cattle,” said Whitlow.

For feedstuffs that test near the critical level of 20 ppb aflatoxin, there are a number of ways producers can manage the problem to salvage feed supplies. “If you have a feed supply that is high in aflatoxin, you can dilute that feed on the farm to reduce the level of aflatoxin fed to the animal,” said Whitlow. Another effective strategy includes screening, or cleaning, corn grain. “Since most of the aflatoxin is in the dust and broken kernels, screening can reduce the aflatoxin level considerably,” stated Whitlow.

On the back end, producers can also reduce the spread of aflatoxin by ensuring that feed is kept in dry, well-aerated storage spaces. “Managing storage and keeping feed dry prevents additional growth of mold and production of aflatoxin,” said Whitlow.

While aflatoxin poisoning remains a common threat to dairy producers, there are about 1,000 varieties of other mycotoxins that can infect silage and feedstuffs of all types, resulting in all sorts of health issues for both animals and consumers.

For a complete breakdown on mycotoxin management and defense strategies, view the embedded iGrow podcast or contact your nearest SDSU Extension field specialist.

January 2013

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