What are Aflatoxins?
Aflatoxins are produced by the Aspergillus fungus. Aspergillus spores occur naturally in the soil and may be transported to grain crops by wind or insects. Aflatoxins affect both native and agricultural grains. Damage to grains from high temperatures, drought or insect infestation may allow colonization of Aspergillus leading to aflatoxin contamination.
Regulations of Aflatoxins
At least 48 countries regulate aflatoxin in food and feed crops. The U.S. set action levels in 1968, following the identification of aflatoxin and its associated animal and human health risks. The FDA can support enforcement action if aflatoxin levels exceed 20 ppb when the feed destination is unknown. While feed for wildlife is included in this standard, it is rarely enforced. This results in the frequent use of contaminated grains to bait and feed wildlife.
Additional information on USFDA action levels and regulatory guidelines can be found at the following websites:
Why the Concern?
Aflatoxin was first identified when it caused the death of commercially-raised turkeys in 1963. Regulation for animal and human consumption soon followed. While aflatoxin has been implicated in mass mortality of waterfowl and other wildlife species, the majority of people involved in wildlife feeding are unaware of the risk it poses to wildlife. Therefore, while it is known to cause many negative effects, the impact of aflatoxin on wildlife populations is largely unknown.
Aflatoxins are known carcinogens. Ingestion of contaminated grains can result in chronic or acute toxicity. Aflatoxin exposure has been characterized by organ dysfunction, internal bleeding and death. Ingestion of small amounts of contaminated grain has been associated with decreased feeding rate and nutrient uptake, decreased reproductive performance, birth defects, tumors and suppressed immune system function.
Wildlife may be exposed to aflatoxins through supplemental feeding and baiting practices. While the lethal concentrations of aflatoxin for wild-bred animals have not been determined, care should be taken to reduce the risk of toxicity in wildlife through thoughtful purchase, storage and dispersal of feed.
Purchasing Grain for Wildlife
Avoid grains with any visible signs of mold growth, as this may indicate the presence of aflatoxins. Aflatoxins are invisible, but mold growth is a strong indicator that aflatoxins could be present. Avoid grains that are “clumping,” as this may indicate the initial stages of mold growth. Purchase grain from reputable dealers, avoiding damaged or waste grain. To reduce storage time, avoid purchasing grain not planned for use in the immediate future.
Aflatoxin production occurs when the Aspergillus fungus has access to the sugar present in grains. Purchasing grains with lower available sugar, such as milo, reduces the chances that aflatoxin will be present at the time of purchase. Damage to grain kernels facilitates aflatoxin contamination. Avoid purchasing visibly damaged grain and intentionally cracked corn. The rapid accumulation of aflatoxin is likely in these products.
Avoid storing grain for an extended period of time. Aflatoxin contamination increases with length of time, regardless of storage container. Avoid storage of grain during warm, moist periods. Stored grain must be kept dry. Avoid extreme temperature fluctuations, as this may cause condensation within the storage container, leading to aflatoxin formation. Grain beginning to form mold or containing any insects should be disposed of immediately.
Reducing the risk of aflatoxin exposure to wildlife is reliant on thoughtful purchase, storage and dispersal of feed.
If feeding wildlife, there are several ways to reduce the risk of aflatoxin contamination.
• First, avoid feeding in warm, moist conditions. Feeding should be limited to times when temperatures are below 60 F. Feeding should not be conducted when rain is expected. Aflatoxin production begins when grain moisture content exceeds 18 percent. Therefore, high humidity and dew may provide sufficient moisture to facilitate the formation of aflatoxin.
• Reduce the length of time that grain persists by limiting the amount of grain dispensed at any given time. The prompt removal of uneaten grain is recommended.
• Never feed damaged grain to wildlife. Grain that has mold or is clumping should not be used as bait or feed.
• Piling grain should also be avoided. Piling grain facilitates the accumulation of moisture, increasing the risk that aflatoxin production occurs. When baiting, disperse grain as much as possible. Broadcast grain when feasible.
• Clean grain feeders regularly with bleach. Avoid refilling grain without first emptying, cleaning, and fully drying feeders.
Leah L. Dale
Associate Professor, Natural Ecology and Resource Management
Wildlife Extension Specialist