Understanding Mycotoxins in Hog Feeds
by Orry Pratt, PFB Intern
Cleanliness of animal feed is critical to any livestock operation, and this is particularly true for swine operations. Feed that is not properly stored can absorb moisture and promote the growth of mycotoxins. This fungal growth has the potential to cause illness and death in animals.
The economic impact of mycotoxin-contaminated feed can be severe, causing U.S. farmers to waste up to $5 billion in mycotoxin-contaminated feed annually. It is important to note that not all mycotoxins are detrimental: some are used to create antibiotics, growth promotants, and other drugs. Aspergillus and Fusarium are two of the most damaging fungi for hogs.
Aspergillus fungus can create aflatoxin which causes weakened immune systems, reduced feed intake, and even death in hogs, and has resulted in costs of over $225 million annually for the corn industry (not including mitigation costs). High temperatures coupled with high moisture levels leads to the growth of this toxin in many grains, including corn, wheat, barley and oats. The mold is abundant in the Southeast United States, but it has also been spotted in the Midwest Corn Belt and the Mid Atlantic States.
Aflatoxin is the only FDA regulated mycotoxin since it can enter the human food chain system. Federal regulation prohibits the interstate transport of toxic feed that occurs in levels of 20 parts per billion or higher.
The Fusarium fungus can produce several different mycotoxins: vomitoxin, zearalenone and fumonisin.
Vomitoxin forms in cool, damp weather, and creates a white or reddish fungus on barley, corn, and wheat crops. While low level occurrences of vomitoxin only reduce feed intake in hogs, higher concentrations of at least five parts per million (ppm) results in feed refusal and vomiting. Losses associated with vomitoxin in the United States have been estimated at $655 million annually, with the majority of the losses in wheat.
Zearalenone is known for causing estrogenic effects in gilts and sows, and like vomitoxin, favors cool, damp conditions, but can be intensified with improper handling and storage techniques. Zearalenone is one of the most harmful mycotoxins to hogs - especially to a breeding herd. Toxicity of the feed can result in swelling and reddening of the vulvas, which is a sign that a pig may be in heat. The fungus is also associated with prolapses and irregular heat cycles, in which fertility problems begin to arise when toxin levels reach one- to two- parts per million.
More recently, fumonisin has been found to affect reproductive systems in hogs and to have had an estimated $18 million impact per year in the swine industry. Little is known about this mycotoxin, but studies have shown that symptoms of fumonisin toxicity include lower live body weights compared to weights of healthy pigs, and weakened immune systems. While fumonisin is found in the Upper Midwest United States, it has also been found in imported grain in Pennsylvania.
In addition to animal feed, mycotoxins also occur in grain by-products. This is a growing problem as grains are increasingly used in producing biofuels. For example, ethanol is derived corn, and a by-product of ethanol production is dried distillers’ grain and solubles (DDGS) which is sold as animal feed. Mycotoxins become more concentrated in DDGS and can prove detrimental for the swine industry.
Management and Testing Strategies
Once contaminated, feed cannot be detoxified. Prevention – specifically proper storage and handling – of mycotoxin growth is essential. Management strategies are an effective way to minimize negative effects of mycotoxins in swine. These include:
Ensure that stored grain is dried and aerated to recommended moisture levels to prevent further mold growth and mycotoxin production.
Avoid feeding mycotoxin contaminated grain to the breeding herd and young pigs. Grow-finish pigs fed for slaughter are the best candidates for tolerating mycotoxin contaminated grain.
If mycotoxin exposure is suspected, give feed to a small “test” group of pigs within the herd. Pre-pubertal gilts are good test subjects for suspected zearalenone (swollen vulvas) and vomitoxin (feed refusal).
If clinical signs of a mycotoxin occur, collect and send samples of suspect grain to an accredited laboratory for testing. It is important that proper collection techniques are used, including random sampling from several locations in a grain batch and periodic sampling from grain during the auguring process. Since plastic bags retain moisture (and increase fungal growth), paper bags should be used to transport the samples. Finally, it is important to note that USDA does not recommend farmers combine contaminated sources with uncontaminated grains.
Economic implications of mycotoxin-contaminated feed are severe and result in billions of dollars wasted on contaminated grain sources. In addition, mycotoxins have the potential for negative impacts on swine herd health if proper feed management methods are not practiced. However, with proper feed management techniques and the acquisition of clean grains, mycotoxins don’t have to appear in commercial swine herds.
For further information about mycotoxin issues, contact:
Or visit these comprehensive websites:
Purdue University - Managing Moldy Corn
EUniversity of Minnesota Extenion - Effect of Mycotoxins in Swine Feed
Penn State University -Wheat Fusarium Head Blight: