Prevention and detoxification methods against mycotoxins
Prevention reduces, not eliminate, the risk of mycotoxin contamination. While detoxification methods reduce its activity and injuries into the animal organism.
Fungal species are roughly divided into field fungi and storage fungi. While the proper conditions for the growth of fungi can occur at any time during crop growth, harvest and storage are the most probable. Therefore, the prevention of mycotoxin production must start on the field prior to seeding and should continue until the animal ingests the feed.
Table 1. Prevention methods for the control of mycotoxins in the field and during storage
|In the field||During storage|
|Land management/crop rotation||Moisture and temperature|
|Crop damage||Physical damage|
In the field
There are many factors that can influence the growth of Fusarium fungi and the occurrence of fusarium toxins in the field. Some preventive measures are available which are based on the knowledge of predisposing factors (1).
Land management/crop rotation
Cropping systems in which maize is rotated with wheat or in which wheat is grown each year in the same field appear to increase mycotoxin contamination. Thus, avoiding this type of rotation can prevent the development of these fungi.
A lot of effort has been invested in plant breeding in recent years. Plant breeding can be considered as the best solution for Fusarium control in susceptible crops (1). However, the alteration in genes responsible to encode mycotoxin resistance can be coincident with morphological changes in the plant, leading also to adverse effects in agronomic properties. One example is the Bt corn varieties which often reduces Fusarium contamination even though may increase the susceptibility of the crop to insects.
Many Fusarium fungi species are soil borne and survive in the crop residues as saprophytes, breaking down plant residues. The spore they form is very resistant to temperature and adverse weather conditions, assuring their survival in crop residues. As a consequence, it is advisable to eliminate residues from the field surface by means of deep tillage.
Stress factors such as high temperatures, drought, poor fertilization, and high competition for nutrients are some of the aspects known to increase mycotoxin production in the field. The choice of the best possible variety of seeds for a certain location, irrigation in critical periods and balanced fertilization are some of the measures that can be used to avoid mycotoxin contamination during plant growth.
Mechanical, insect or bird damage of grains provides a good opportunity for fungal invasion and development, thus the prevention of such damage is of major importance.
A suitable harvesting date is extremely important to avoid fungal growth and subsequent mycotoxin contamination, as unstable weather conditions such as late rain will exponentially increase its occurrence.
Moisture and temperature
The interaction between moisture level and temperature is the most important physico-chemical factor affecting preservation of commodities and feeds during storage. Ideally, both should be kept as low as practicable, if the moisture level is sufficiently high, fungi can develop even at low temperatures (5 to 10°C) (2). Temperature fluctuations (rise of 2-3°C) may also be a sign of microbial growth and/or insect infestation. Make sure storage facilities are dry and present minimum temperature fluctuations.
Mould growth in grains is usually occurring heterogeneously, therefore the development of “hot spots” (areas in which the concentration of mycotoxins is higher) is common. This happens because warm air within the grains and feed comes into contact with cooler air, promoting an interchange of moisture and increasing the odds of condensation occurrence. Once again, these high-moisture spots are an incentive for fungal germination (2). The aim of aeration is to cool the grain, but maintaining it in constant movement will increase the efficiency of storage. However, note that dust coming from the outside of the grain is hygroscopic – and has often higher moisture content – and carries a higher proportion of fungal spores than whole clean grain. When possible, aerate the stored goods by circulation of air through the storage area to maintain proper and uniform temperature levels throughout the storage area.
Fungal development is likely to occur at several points of the storage to feeding pathway, including storage bins, the feed mill, mixed feed bins, pipelines of the feeding system and ultimately in animals feeders. The use of fungistatic agents is a common management practice which can be very efficient in reducing mold growth and further mycotoxin production (3). Nevertheless, it should be emphasized that once the mould has already damaged grain and/or produced mycotoxins, the effectiveness of this practice is very limited. It is also important to bear in mind that sublethal applications of fungicides are known to stimulate mycotoxin formation. This is likely to occur because fungi are stressed, but not killed (4). So, in case fungicides are used, product’s instructions should be carefully carried out in order to avoid this occurrence. Chemicals used should not interfere with the intended end use of the goods. Cleaning of equipment on a regular basis is highly recommended.
It is a general designation for insects, arthropods, rodents or birds which can contribute to the contamination of the kernel. These organisms can act in two main ways, by destroying the physical integrity of the grains and serving as carriers of mould spores and their fecal material can be utilized as food source by moulds (5). Use good housekeeping procedures to minimize the levels of pests in the storage facilities.
Although most mould pathogens can directly penetrate plant tissues, it is important to avoid mechanical and insect damage. Broken kernels caused by general handling and/or insect damage provide additional entry sites for mould pathogens, facilitate infection and promote distribution throughout the grain mass (6).
Detoxification procedures after harvest are necessary due to the fact that preventive methods during crop growth, harvesting and storage reduce, but do not eliminate the potential risk of mycotoxin contamination. These processes should deactivate, destroy or remove the toxin and fungal spores, while retaining the nutrient value and acceptability of the feed by the animal. Furthermore, the deposition of toxic substances, metabolites or toxic by-products in the feed can be avoided, as well as significant alterations in the product’s technological properties.
Broken kernels are more easily infected by fungi and, therefore, mycotoxins than intact kernels. Not only this, as mentioned before, grain dust is likely to transport fungal spores, which will increase the odds of mycotoxin production. The main objective of the cleaning process is to remove contaminated grain dust, husks, hair and shallow particles by aspiration or scouring.
Mechanical sorting and separation
In this process, the clean product is separated from mycotoxin-contaminated grains. High feed losses are possible due to incomplete and inaccurate separation. Therefore, mechanical sorting and separation is not cost-efficient.
Washing procedures using water or sodium carbonate solution are reported to result in some reduction of mycotoxins in grains (7). This process, however, may only be used in feeds or commodities which will undergo wet milling or ethanol fermentation otherwise costs of drying would be prohibitive.
Grain flotation can be used for the segregation of contaminated grains. This method can reduce mycotoxin contamination, but it should be noted that the appearance and weight of a particular kernel does not necessarily indicate mycotoxin contamination.
Mycotoxins are very heat stable, therefore, heat treatments like boiling water, roasting, pelleting or even autoclaving cannot destroy them adequately.
Some experiments have been done involving the use of irradiation to reduce the mycotoxin load of commodities (8, 9, 10). However, while the results showed a reduction in fungal spore contamination, there was no reduction in terms of the mycotoxins already present in the material.
Various chemicals (many acids, bases, aldehydes, bisulfite, oxidizing agents and different gases) have been tested for the detoxification of mycotoxins, but only a limited number of chemical methods are effective against mycotoxins and might be used in practice without forming toxic residues or having a negative effect on nutrient content, flavor, color, texture, and/or functional properties of the feedstuff/feed (11).
The addition of adsorbent materials to animal feeds is a very common method to prevent mycotoxicosis, especially aflatoxicosis. These compounds bind mycotoxins when they are mixed in a wet environment, such as the gastrointestinal tract, thus reducing the mycotoxins entering the bloodstream (12, 13). Efficacious adsorption of mycotoxins depends on the polarity and shape of the mycotoxin, and on the type of bond that is formed between the toxin and the adsorbent. Because of these conditions, only a few mycotoxins can be adsorbed efficiently (e.g. aflatoxins) (1, 12). The adsorption efficacy of the most important mycotoxins is shown in Figure 1.
Mycotoxins are biotransformed into non-toxic metabolites either by specific purified enzymes or microorganisms that produce the respective specific enzymes in a respective environment. This approach is based on the deactivation of mycotoxins directly in the gastrointestinal tract or a similar environment, and offers a very specific, irreversible and efficient way of detoxification.
Insure high quality in mycotoxin counteraction
EU registration is considered a benchmark for quality of mycotoxin deactivation products. It evaluates the identity, safety and efficacy of the product in a standardized process by using biomarkers to directly prove the deactivation of mycotoxins in vivo.
- Fumonisins: No 1115/2014, 2017/913, 2018/1568, 2021/363
- Aflatoxins: No 1060/2013
- Trichothecenes: No 1016/2013, 2017/930
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- Krska R., Nährer K., Richard J. L., Rodrigues I., Schuhmacher R., Slate A. B., Whitaker T. B., (2012). Guide to Mycotoxins featuring Mycotoxin Risk Management in Animal Production. BIOMIN edition 2012
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