What are mycotoxins and aflatoxins?
Mycotoxins are naturally-occurring substances produced by fungi growing on food and animal feed. Aflatoxins are the most toxic group of mycotoxins, produced by two species of fungi Aspergillus flavus and A. parasiticus, usually in areas with hot and humid climates. Aflatoxins can be found in many crops including peanuts, corn, cottonseed, Brazil nuts, pistachios, spices and figs. Several forms of aflatoxins are known, such as aflatoxin B1 , B2, G1 , G2 and M1 . Aflatoxin M1 , a metabolite of aflatoxin B1 can be found in the milk of lactating animals and humans that consume aflatoxin B1 contaminated food or feed. SR In cows, around 1 -6% of the aflatoxin is carried over to the milk. As summarized in table 1 , the effects of aflatoxins in farm animals can be severe. Aflatoxins decrease performance (weight gain, milk and egg production), suppress the immune system, cause liver damage and reduce reproduction. Human aflatoxicosis are still of concern for the food industry. A severe outbreak in Kenya in 2004 resulted in 31 7 cases of aflatoxicosis and 1 25 deaths, whereby 55% of the maize food samples tested exceeded Kenya’s regulatory limit. Exposure to aflatoxins through food and feed should be kept as low as possible.
In the past months, news have highlighted extreme hot weather and poor rainfall in the U.S. This was the most severe and extensive drought since 1 956 which seriously affected U.S. agriculture with impacts on the crop and livestock sectors. Fungal growth and the ability to produce mycotoxins like aflatoxins, are dependent on climatic conditions.
Heat and drought stress are known to favor the growth of Aspergillus flavus and Aspergillus parasiticus, the fungi producing aflatoxins. The process of aflatoxin contamination can be divided in a two critical phases. The first critical phase of infection occurs during crop development. Due to the stress caused by hot and dry weather conditions, the developing crop is more susceptible to infection. The second phase of contamination and increase of aflatoxin concentration occurs, when the mature crop is exposed to warm, moist conditions on the field, during transport and storage. Rain just before or during harvest, is associated with increased aflatoxin occurrence. Due to changing weather patterns, even well planned crops in usually aflatoxin free areas may become exposed to conditions favorable for contamination. In 2003, an outbreak of Aspergillus flavus, resulted in aflatoxin in maize which was previously uncommon in Europe. Influence of climate change Aflatoxins, which are frequent in tropical and sub-tropical regions, could become a concern in parts of Europe and the USA due to climate change. EFSA’s Emerging Risks Unit published a predictive model to calculate the possible impact of climate change on aflatoxin occurrence in grain in the EU-region. An increase in temperature by +2°C could shift the aflatoxin risk zones for maize towards northern areas, resulting in high aflatoxin risk in southern EU countries and low and medium aflatoxin risks in the four main maize production countries (Romania, France, Hungary and northeast I taly; 73% of the total EU-27 production). The impact of climate change was identified as an emerging issue for food and feed safety.
Mycotoxin Risk Management
It is important to implement an effective and long lasting mycotoxin risk management in combination with appropriate farm management. Agricultural techniques have been developed to prevent mold growth and mycotoxin production, like crop rotation, tillage, weed and insect control and selecting the correct dates for planting and harvesting. The humidity level and temperature before and during storage needs to be ontrolled.
As prevention strategies have their limitations, intensive research was conducted in the last three decades, to deactivate mycotoxins. One of the strategies for reducing the exposure to mycotoxins, is to decrease their bioavailability by including mycotoxin-adsorbing agents in the compound feed. Aflatoxins can be adsorbed due to their high polarity by anorganic binders such as bentonite. As binders can differ widely in their selective adsorption capacity without affecting essential feed ingredients, such as vitamins and minerals, it is important to verify the quality of a binder by a broad range of experiments.
The maximum levels of aflatoxins in feed and food are strictly regulated in most of the countries worldwide. Regulations may also include detailed sampling procedures, as this is one of the most crucial steps in ensuring reliable results. The amount of aflatoxin can differ in crop coming from the same region and even from the same field. The European Commission (through the Standing Committee on the Food Chain and Animal Health) has recently raised awareness that there could be higher concentrations of aflatoxin B1 in this year’s maize crop from some member states of the EU.
The United Nations’ forecasts for this year’s harvest indicated, that world cereal production will be reduced by 2.6 %, due the drought in the U.S. , rain in Europe and erratic weather in Asia. Eroded crop conditions and crop losses along with an increase in price per bushel are forcing the agricultural industry to import corn from other regions of the world. Global trade in agricultural commodities contributes to the concern about the mycotoxin hazard and increases the awareness of potential “imported problems”. Grain purchasers often reject or pay lower prices for corn tested positive for aflatoxins.
In some US States – I l l inois, Indiana, Iowa, Kansas, Nebraska and Oklahoma – FDA has granted a blend agreement for corn wi th aflatoxin content >20 ppb for animal feed and by-products of bioethanol (limit 300 ppb). Each batch of blended corn must be analysed and only corn containing <500 ppb can be used for blending. Note, that blended corn may not be used for human food (limit 200 ppb).
Christina Schwab, PhD – Biomin Holding GmbH Product Manager
Laetitia Cirilli, PhD – Fami-Qs Manager
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