A wide overview on mycotoxin risk management
Effective management of mycotoxins is key for animal production, especially with the trends moving towards antibiotic reduction or even antibiotic free production. There are different ways to manage mycotoxins, and to simplify, in this article we will divide those in two main categories: management at the farm and management in the feed.
Managing mycotoxins at the farm
Production of mycotoxins is largely driven by three factors:
- plant and environmental factors, including substrate characteristics (e.g. composition of soil, pH, water activity, oxygen content)
- possible competitive actions (e.g. associated growth of other fungi or microbes)
- climatic conditions (e.g. temperature, atmospheric humidity, drought)
Human activities can partially mitigate some of those factors, maximizing plant performance, reducing stress and consequently minimizing the growth of fungi and mycotoxin production, but cannot fully eliminate them. These include good agricultural practices (GAP), the precondition to minimizing the contamination of grains with mycotoxins, and good manufacturing practices (GMP) that deal with the handling, storage, processing and distribution of cereals.
Minimizing mycotoxins on the field
Breeding of resistant or less susceptible grains can help to prevent fungal growth and mycotoxin production, however, field fungi like Fusarium are very adaptable and might find a way to still grow and produce mycotoxins.
The sowing time has an impact on the flowering stage of the plant: the earlier the planting date, the earlier the flowering stage. Mycotoxin contamination is highest when the crop reaches its flowering stage.
Correct irrigation reduces plant stress, but excessive irrigation could contribute in favoring the dissemination of Fusarium sp., especially during flowering and ripening of the crops.
Cropping systems where maize is rotated with other cultivars such as rapeseed, sugar beet, sunflower or soybeans might reduce fungal growth and the appearance of mycotoxins.
Mechanical, insect or bird damage of grains provides a good opportunity for fungal infection, thus their prevention is of major importance.
Proper soil tillage and management of residues on the field are imperative to reduce the risk of mycotoxin contamination. For example, ploughing (10-30 cm into the soil) is more effective against mycotoxin contamination compared to minimum tillage (10-20 cm into the soil) and no tillage (seeds drilled into previous crops). Post-harvest ploughing can reduce the growth of F. graminearum. In addition, the removal, burning or burial of crop residues can reduce the occurrence of Fusarium species in the following crops.
There is evidence that the correct use of fertilizers can affect the contamination level of Fusarium sp., influencing the plant growth and changing the soil structure along with its microbial activity.
Weeds can contain a broad range of Fusarium species. Any crops that are highly weedy, for example wheat, will have a higher risk of contamination.
Harvesting at the appropriate time is essential for reducing the risk of mycotoxin contamination. In general, early harvest leads to lower concentrations of mycotoxins. Additionally, special attention should be paid to proper drying of the grain.
Using appropriate harvest equipment is key to avoid damage to the grains, and predisposing them to infection during storage. Additionally, the equipment should be free from residual grain from the previous harvest to avoid cross contamination.
Managing mycotoxins during storage
A general rule of thumb is to store grains when they reach 15% humidity or lower. Water in the grain creates an ideal growth environment for fungi. The water activity (aw) of the grain should be kept below 0.65 and the humidity or total water content below 140 g/kg to prevent fungal growth. Atmospheric humidity can play an important role too, as it varies a lot between morning dew and afternoon sunshine.
Besides humidity, managing the temperature during storage is also important for the control of fungal growth. To combat fungal growth, combined cooling and drying operations together with ventilation systems are necessary to avoid further contamination. Another way to reduce the presence of wet spots inside the silo is to rotate the grain from time to time.
Managing mycotoxins in the feed
The most effective way to fully eliminate mycotoxins is to tackle them directly in the gastrointestinal tract of animals. The most common ways to do so are adsorption and biotransformation. The addition of adsorbent materials (aka binders) to animal feeds is a very common method to prevent mycotoxicosis, especially aflatoxicosis. These compounds bind mycotoxins in the gastrointestinal tract, thus reducing the number of toxins going into the blood stream. Mycotoxins such as aflatoxins have a flat chemical structure and can be trapped between the layers of bentonites, in the same way a slice of meat sits between two slices of bread in a sandwich. Once the mycotoxin enters the binder layers, the electric force generated by the atoms of both compounds tightens the bond. The less flat chemical structure of other mycotoxins like deoxynivalenol or zearalenone results in less effective adsorption. One important remark is that even for aflatoxins, not all binders act in the same way: in the European Union (EU), there are rigid requirements that are needed to demonstrate the efficacy both in vitro and in vivo. Companies that claim aflatoxin adsorption need a registration and need to fulfill the strict requirements imposed by EFSA (European Food and Safety Authority).
The term biotransformation stands for the chemical modifications carried out by enzymes produced by microorganisms on chemical compounds (e.g. mycotoxins). This approach is based on the deactivation of mycotoxins directly in the gastrointestinal tract and offers a very specific, irreversible and efficient way of detoxification. This strategy is particularly suitable towards less or non-adsorbable mycotoxins and it currently represents the state of the art detoxification approach. Biotransformation is regulated only in the EU and currently only one company holds five EU registrations on deoxynivalenol and fumonisins, which are the undisputed proof of identity, safety and efficacy of mycotoxin-deactivating enzymes, both in vitro and in vivo.
In conclusion, mycotoxin management is a 360° effort that starts on the field before sowing, and ends in the gastrointestinal tract of animals. Mycotoxin contamination has increased worldwide and recent studies showed that up to 80% of crops can be contaminated by a number of different mycotoxins and bacterial metabolites simultaneously. The effects of the exposure to those cocktails of chemicals are still largely unknown, but more light has been shed on the synergistic interactions that might occur between different mycotoxins at subclinical doses. The ultimate weapon to win the war against mycotoxins in animal production is to rely on feed additives which mode of action has been proven and validated by third parties. The EU has already established such a system and we urge other markets to do the same, in order to ensure quality, safety and efficacy to animal and grain producers.
For more of the article, please click here.
Article made possible through the contribution of Michele Muccio and BIOMIN