Mycotoxins are toxic compounds produced by fungi that occur naturally in grains. When consumed at elevated levels, mycotoxins may cause sickness in humans and animals. While several mycotoxins have been found in sorghum and other grains, aflatoxins and deoxynivalenol (DON or vomitoxin) are considered to be two of the important mycotoxins.
The 2015 harvest samples were tested for aflatoxins and DON for this year’s report. Since the production of mycotoxins is heavily influenced by growing conditions, the objective of the Harvest Survey is strictly to report on instances when aflatoxins or DON are detected in the sorghum crop at harvest. No specifc levels of the mycotoxins are reported.
The Harvest Survey review of mycotoxins is NOT intended to predict the presence or level at which mycotoxins might appear in U.S. sorghum exports. Due to the multiple stages of the U.S. grain merchandising channel and the laws and regulations guiding the industry, the levels at which mycotoxins appear in sorghum exports are less than what might first appear in the sorghum as it comes out of the field. In addition, this report is not meant to imply that this assessment will capture all the instances of mycotoxins across all of the top sorghum-producing states surveyed. The Harvest Survey’s results should be used only as one indicator of the potential for mycotoxin presence in the sorghum as the crop comes out of the field. As the Council accumulates several years of the Sorghum Harvest & Export Cargo Reports, year-to-year patterns of mycotoxin presence in sorghum at harvest will be seen. The “Export Quality Test Results” section will report sorghum quality at export points and will be a more accurate indication of mycotoxin presence in the 2015/2016 U.S. sorghum export shipments.
ASSESSING THE PRESENCE OF AFLATOXINS AND DON
A weighted and systematic testing of at least 25% of the targeted 200 samples across the entire sampled area was conducted to assess the impact of the 2015 growing conditions on total aflatoxins and DON development in the U.S. sorghum crop. The sampling criteria, described in the “Survey and Statistical Analysis Methods” section, resulted in a targeted number of 58 samples tested for mycotoxins.
A threshold established by U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS) as the “Lower Conformance Level” (LCL) was used to determine whether or not a detectable level of the mycotoxin appeared in the sample. The LCLs for the analytical kits approved by FGIS and used for this 2015/2016 report were 5.0 parts per billion (ppb) for aflatoxins and 0.5 parts per million (ppm) for DON. The FGIS LCL was higher than the Limit of Detection (LOD) specified by the kit manufacturer of 2.0 ppb and 0.1 ppm for aflatoxin and DON, respectively. Details on the testing methodology employed in this study for the mycotoxins are in the “Testing Analysis Methods” section.
A total of 58 harvest samples were analyzed for aflatoxins in 2015. Results of the 2015 Harvest Survey are as follows:
- All fifty-eight (58) samples, or 100% of the 58 survey samples, had no detectable levels of aflatoxins (sample test results were less than or equal to the FGIS LCL of 5.0 ppb).
- No samples (0), or 0.0% of the 58 samples, showed aflatoxin levels greater than the LCL of 5.0 ppb, but less than or equal to 10 ppb.
- No samples (0), or 0.0% of the 58 samples, showed aflatoxin levels greater than 10 ppb, but less than or equal to the Food and Drug Administration (FDA) action level of 20 ppb.
- No samples (0), or 0.0%, of the 58 samples, showed aflatoxin levels greater than the FDA action level of 20 ppb.
All survey samples from the 2015 crop season tested below the FGIS LCL value of 5.0 ppb, indicating that the contamination level in the domestic crop was potentially minimal. This may have been due, in part, to favorable weather conditions in 2015 (see the “Crop and Weather Conditions” section for more information on the 2015 growing conditions). Weather was cool and wet in 2015 and as a result, the plants were not under stress. These conditions were not conducive to aflatoxin formation.
RESULTS: DON (DEOXYNIVALENOL OR VOMITOXIN)
A total of 58 samples was analyzed collectively for DON in 2015. Results of the 2015 survey are shown below:
- All fifty-eight (58) samples, or 100.0% of the 58 survey samples, had no detectable levels of DON (all samples tested less than or equal to the FGIS LCL of 0.5 ppm).
- No samples (0), or 0.0% of the 58 samples, tested greater than 0.5 ppm, but less than or equal to the FDA advisory level of 5 ppm.
- No samples (0), or 0.0% of the 58 samples, tested greater than the FDA advisory level of 5 ppm.
- In 2015, all 58 samples, or 100%, tested below the FDA advisory level of 5 ppm.
In 2015, all 58 samples, or 100%, tested below the FDA advisory limit of 5 ppm. In fact, all survey samples tested below the FGIS LCL threshold of 0.5 ppm, indicating that the DON contamination level in the domestic crop was potentially minimal. The fact that all survey samples tested below the FGIS LCL threshold of 0.5 ppm may be due, in part, to weather conditions less conducive to DON development in 2015 (see the “Crop and Weather Conditions” section for more information on the 2015 growing conditions).
1. Background: General
The levels at which the fungi produce the mycotoxins are impacted by the fungus type and the environmental conditions under which the sorghum is produced and stored. Because of these differences, mycotoxin production varies across the U.S. sorghum-producing areas and across years. In some years, the growing conditions across the sorghum-producing regions might not produce elevated levels of any mycotoxins. In other years, the environmental conditions in a particular area might be conducive to production of a particular mycotoxin to levels that impact the sorghum’s use for human and livestock consumption. Humans and livestock are sensitive to mycotoxins at varying levels. As a result, the FDA has issued action levels for aflatoxins and advisory levels for DON by intended use. Action levels specify precise limits of contamination above which the agency is prepared to take regulatory action.
Action levels are a signal to the industry that the FDA believes it has scientifc data to support regulatory and/ or court action if a toxin or contaminant is present at levels exceeding the action level, if the agency chooses to do so. If import or domestic feed supplements are analyzed in accordance with valid methods and found to exceed applicable action levels, they are considered adulterated and may be seized and removed from interstate commerce by the FDA.
Advisory levels provide guidance to the industry concerning levels of a substance present in food or feed that are believed by the agency to provide an adequate margin of safety to protect human and animal health. While the FDA reserves the right to take regulatory enforcement action, enforcement is not the fundamental purpose of an advisory level.
A source of additional information is the National Grain and Feed Association (NGFA) guidance document titled “FDA Mycotoxin Regulatory Guidance”, which can be found at http://www.ngfa.org/wp-content/uploads/NGFAComplianceGuide-FDARegulatoryGuidanceforMycotoxins8-2011.pdf.
2. Background: Aflatoxins
The most important type of mycotoxin associated with sorghum grain is aflatoxin. There are several types of aflatoxin produced by different species of Aspergillus, with the most prominent species being A. flavus. Growth of the fungus and aflatoxin contamination of grain can occur in the field prior to harvest or in storage. However, contamination prior to harvest is considered to cause most of the problems associated with aflatoxin. A. flavus grows well in hot, dry environmental conditions, or where drought occurs over an extended period of time. It can be a serious problem in the southern United States, where hot and dry conditions are more common. The fungus usually attacks only a few kernels on the plant and often penetrates kernels through wounds produced by insects.
There are four types of aflatoxin naturally found in foods – aflatoxins B1, B2, G1 and G2. These four aflatoxins are commonly referred to as “aflatoxins” or “total aflatoxins.” Aflatoxin B1 is the most commonly found aflatoxin in food and feed and is also the most toxic. Research has shown that B1 is a potent, naturally occurring carcinogen in animals, with a strong link to human cancer incidence. Additionally, dairy cattle metabolize aflatoxin to a different form of aflatoxin called aflatoxin M1, which may accumulate in milk.
Aflatoxins express toxicity in humans and animals primarily by attacking the liver. The toxicity can occur from short-term consumption of very high doses of aflatoxin-contaminated grain or long-term ingestion of low levels of aflatoxins, possibly resulting in death in poultry and ducks, the most sensitive of the animal species. Livestock may experience reduced feed effciency or reproduction, and both human and animal immune systems may be suppressed due to aflatoxin ingestion.
The FDA has established action levels for aflatoxin M1 in milk intended for human consumption and aflatoxins in human food, grain and livestock feed (see table below).
The FDA has established additional policies and legal provisions concerning the blending of grains with levels of aflatoxins exceeding these threshold levels. In general, the FDA currently does not permit the blending of grains containing aflatoxin with uncontaminated grain to reduce the aflatoxin content of the resulting mixture to levels acceptable for use as human food or animal feed.
If required by the buyer, sorghum exported from the United States will be tested for aflatoxins by FGIS. Sorghum above the FDA action level of 20 ppb or the buyer’s specifcation cannot be exported unless other strict conditions are met. These requirements result in relatively low levels of aflatoxins in exported grain.
3. Background: DON (Deoxynivalenol or Vomitoxin)
DON is another mycotoxin of concern to some importers of sorghum grain. It is produced by certain species of Fusarium, the most important of which is Fusarium graminearum (Gibberellazeae). Gibberellazeae can develop when cool or moderate and wet weather occurs at flowering. Mycotoxin contamination of sorghum caused by Gibberellazeae is often associated with excessive postponement of harvest and/or storage of high-moisture sorghum.
DON is mostly a concern with monogastric animals, where it may cause irritation of the mouth and throat. As a result, the animals may eventually refuse to eat the DON-contaminated sorghum and may have low weight gain, diarrhea, lethargy, and intestinal hemorrhaging. Additionally, DON may cause suppression of the immune system resulting in susceptibility to a number of infectious diseases.
The FDA has issued advisory levels for DON. For grain products, the advisory levels are:
- 5 ppm in grains and grain co-products for swine, not to exceed 20% of their diet;
- 10 ppm in grains and grain co-products for chickens and cattle, not to exceed 50% of their diet; and
- 5 ppm in grains and grain co-products for all other animals, not to exceed 40% of their diet.
FGIS is not required to test for DON on sorghum bound for export markets, but will perform either a qualitative or quantitative test for DON at the buyer’s request.