CONTACT: Julie Martinez
or Alan Fedynich
AFLATOXIN TAINTED FEED
COULD HURT WILD GAME
KINGSVILLE (Oct. 27, 1998) -- Supplemental feeding of game species such as white-tailed deer and bobwhite quail is a common practice on many Texas ranches. Some urban and suburban landowners also use backyard feeders to attract birds to view and photograph.
However, supplemental feeding may present a problem for wildlife in the form of aflatoxins, said researchers Dr. Scott Henke and Dr. Alan Fedynich of Texas A&M University-Kingsville's Caesar Kleberg Wildlife Research Institute.
Aflatoxin is a poisonous substance produced by the fungi Aspergillus flavus and Aspergillus parasiticus. The toxin is produced by the fungi as a defense mechanism to keep it from being eaten. The fungi commonly grows on feed pellets, fodder and cereal grains.
The fungi is a concern even for humans as the United States Food and Drug Administration does not allow grain tested at more than 20 parts per billion to be fed to dairy cattle or to be used in grain products headed for human consumption. However, grain tested at over 20 parts per billion can be used as wildlife feed.
Henke and Fedynich have been concerned about how aflatoxin is impacting wildlife in South Texas. They are conducting studies to learn more about the problem.
Grain for human or livestock consumption is tested, but that sold for wildlife feed may or
may not be tested, Henke said. "Aflatoxin concentrations in commercially available wildlife feed may be at levels sufficient to cause chronic poisoning."
To determine how bad the problem is, researchers at Texas A&M University and the Texas Agricultural Extension Service, both at College Station, examined levels of aflatoxin found in bagged corn marketed for sale as deer or wildlife feed at retail outlets across the state.
They found almost half of the 100 samples tested contained levels considered potentially hazardous for wildlife. Forty-four percent of those contained levels higher than 20 parts per billion and 20 percent had levels at 100 parts per billion or higher. The Texas Feed and Fertilizer Control Service recommends that grain tested higher than 100 parts per billion not be used to feed free-ranging deer.
"The high levels of aflatoxin found in feed corn this year has prompted many to re-evaluate wildlife feeding programs that use corn as a supplement," Fedynich added. "Texas Parks and Wildlife has issued alerts regarding the potential danger of feeding aflatoxin-contaminated feed to wildlife."
Little information is available concerning the effects of aflatoxin on wildlife and guidelines are generally based on toxicity studies conducted on domesticated animal species like cattle, chickens and turkeys. The few studies on wildlife have focused on economically-important game species such as white-tailed deer (fawns), bobwhite quail and wild turkeys.
"These studies have found that high levels of aflatoxin consumption caused liver damage, immune system dysfunction and left the animals in generally poor health," Fedynich said. "Little is known about the long-term effects on individuals and populations from chronic exposure to aflatoxin or its effect on nongame species."
"Unfortunately, many people think that aflatoxin is a 'game species' problem but the scope is much wider, particularly when one considers thousands of urban and suburban Texans feeding songbirds at their back yard bird feeders," Fedynich said. "We know very little about the rate of exposure or for that matter, the impact of acute or chronic exposure of aflatoxin on songbirds, small mammals and other nongame wildlife in Texas."
Henke has been studying aflatoxin for several years. "One of the big misconceptions about aflatoxin is that if a grain bag is labeled as having a certain level of aflatoxin then that is what you are actually putting out there for wildlife," he said. "However, that was the aflatoxin level when it was tested, which could have been months ago.
"Since aflatoxin-producing fungi can continue to grow on grain in the bag and under a variety of conditions, the level of aflatoxin is likely to be much higher by the time it is actually fed to wildlife. The only way to determine the level of aflatoxin that wildlife are actually being exposed to is to test it as it is dispensed from the feeder."
Henke said many people also put 'clean' corn into aflatoxin-contaminated feeders, which defeats the purpose of buying aflatoxin-free grain in the first place.
Poor storage practices that allow grain to become wet or moist also encourage mold growth. "A common misconception about aflatoxin is that if somebody buys grain that tests out, for example, at 20 part per billion, and just stores the grain correctly, the feed will be fine to feed wildlife," Henke said. "My study found that no one storage practice short of freezing the grain effectively curtailed the growth of fungi-producing aflatoxin.
"Growth occurred under hot and dry conditions, hot and wet conditions, cold and dry conditions and cold and wet conditions. Also, the storage bag type, paper or plastic, did
not seem to curb growth."
One of the methods that has been suggested to test grain at home and avoid costly lab testing is to run a black light over the grain. If aflatoxin is present, it will glow when exposed to the ultraviolet light generated from a black light.
"The studies I conducted suggest this method is accurate only about half the time and the method does not indicate the actual concentration of aflatoxin on the grain which makes this method essentially useless," Henke said.
Both Henke and Fedynich believe that additional studies are needed to determine the full impact of aflatoxin on Texas wildlife and to find effective solutions that are both economically feasible and practical.
"Effectively managing wildlife is an important goal of many landowners and wildlife managers in Texas," Fedynich said. "It is important to determine if certain practices such as supplementally-feeding wildlife with low levels of aflatoxin are actually harmful to wildlife and what can be done to reduce or eliminate the problem so wildlife are not harmed."