By Dr. Max F. Hawkins, Nutritionist at Alltech:
Precursor for Aspergillus, the mold responsible for aflatoxins
Much has been written and reported to date about the growing season and condition of the 2012 corn crop. The abnormally dry and hot spring and summer of 2012 has initiated articles and reports on pricing, producer profitability, availability for users, increases in food prices and a long list of other topics. As of this writing, there have been more than 1000 counties in 26 states declared as disaster areas, and with the forecast for the next 30 days, there could be more as the drought continues. Even if one is not in the severe drought area, the crop has more than likely been stressed by the heat and lack of normal rainfall.
In the areas where the drought has been the worst, growers are mowing down severely stunted corn. There are producers beginning to calculate if the crop will have enough yield and return to afford the harvest. However, there are some other concerns that producers and users need to consider during harvest.
In 2009, the cool and wet season was a precursor for Fusarium mold growth in the corn crop. This led to a higher than normal level of DON, or vomitioxin, across a wide area of the cornbelt.
The extreme hot and dry growing season of 2012 is a precursor for Aspergillus, the mold responsible for aflatoxins. If the corn has been further damaged or stressed by insects or hail, the chance for aflatoxin is greater. Aspergillus can produce different aflatoxin toxins. There can be aflatoxin B1, B2, G1 or G2. Unlike other mycotoxins, the levels of these in corn are regulated by the FDA, as they are a carcinogen.
It is highly recommended to test for aflatoxin. Testing can begin in the field by taking several samples, representing the entire crop in the field, and then pooling them together for a sample to test. As with all mycotoxin testing, the test itself is only
as good as the sample. Mycotoxins can be located in certain areas and not in others, or on one kernel and not the one next to it. Common quick tests are to use a black light or a specific ELISA kit. The black light test estimates the
Aspergillus mold, not the aflatoxin produced. It also can be as much as 25 percent inaccurate in its estimate. The ELISA test requires some basic chemistry and estimates the aflatoxin present, but they will not quantify precise amounts and which aflatoxins are present. This is important because, of the four separate aflatoxins mentioned previously, they can have an additive or synergistic interaction with other mycotoxins. An additive effect is an “addition to” effect. By adding up all of the mycotoxins present, to get the total amount that will effect animal production. Synergistic effects are when two or more mycotoxins at low levels have an interactive effect and the result is a higher effect than the total of the parts.
The most definitive and encompassing testing method is LC-MS2. This is the technology that Alltech has employed in their 37+ mycotoxin testing program. This mass spectrometry technique utilizes the high sensitivity and selectivity of liquid chromatography to enhance definition and quantification of mycotoxins. LC-MS2 combines separation capabilities (LC) with the accurate detection of mass particles (MS). MS2 is a mass spectrometer capable of doing several rounds of mass spectrometry separated by mass fragmentation. This approach allows the recording of the analyte’s atomic mass or fragments and its unequivocal assignment with its fragmentation, enabling its specific fingerprinting.
Aflatoxin can continue to grow in the stored grain if conditions are right. Storage growth will occur if moisture is over 12 percent and the temperature is a 70 degrees Fahrenheit and above. Grain needs to be dried quickly and cooled with fines removed to ensure proper control of aflatoxin.
A second mold to be on the lookout for in dry and hot weather is Fusarium verticillioides, which produces the mycotoxin fumonisin B1. Fumoisin B1 is a serious consideration with its effects on horses, Equine Leukoencephalomalacia (ELEM) and Porcine Pulmonary Edema in swine. F. verticillioides needs a corn plant to be drought stressed and temperatures over 80 degrees Fahrenheit to flourish, and can affect the root system, the stalk and the ears. Fusarium Ear Rot is the sign typically seen in the fields.
Fusarium verticillioides over-winters in debris, both in or on the surface of the fields. Corn plants can be infected through the silk channel, splashed material on the leaves and stalk into injured areas, or through wounds to the ears by insects, birds or hail.
The next precursor in the 2012 crop deals with the storage of silage and the development of Penicillium. Penicillium (Figure 5)is a storage mold that is always present year to year, regardless of the environment in the field. Penicillium will flourish in silage that is dry (greater than 35% dry matter), poorly packed, and has a significant amount of soil contamination. Penicillium is the most common storage mold and produces PR toxin, patulin, mycophenolic acid, roquefortine C , penicillic acid, and ochratoxin as mycotoxins. These mycotoxins are lactic acid tolerant and can form more quickly in dry, poorly packed silage. When the storage is opened up and exposed to oxygen, these toxins will multiply rapidly. Penicillium produced mycotoxins are potent and powerful. They have an antibiotic effect in the rumen and effect VFA concentrations.
PR toxin is related to reduced intake, rumen stasis, intestinal irritation, abortion and retained placenta. Roquefortine C and Mycophenolic Acid are associated with toxic silage, but are under more study to fully understand their implications. Ochratoxin is a kidney toxin, toxic to young calves, but does not affect functional ruminants as severally. Typical effects are oxidative stress, ketosis through impairment of VFA metabolism, and liver damage.
The 37+ mycotoxin analysis developed by Alltech can identify the presence and concentrations of these individual Penicillium mycotoxins, even at the low levels that form additive and synergistic effects.
The 2012 corn crop has already been impacted for yield and quality. The corn belt is preparing for a less than ideal situation, but don’t get caught just watching yield. Be aware of the total potential of the situation.
Editor’s Note: This commentary is sponsored by Alltech, Inc. For more information on animal health and nutrition, go to: www.alltech.com
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