Can mycotoxins force an upper limit of corn usage in animal feeds?

Corn is the major raw material used in animal feeds. In pigs and poultry, corn represents up to 60% of the diet while in ruminants it is used as grain, silage, and many by-products with varying levels of inclusion. As corn is an excellent source of the majority of the nutrients required in animals’ diets, it is hard to find a suitable replacement. Can mycotoxins lower the limit of corn usage?

MAJOR MYCOTOXINS OF CONCERN IN CORN
More than 600 mycotoxins have been identified chemically and the number is increasing every passing year. Climate change, improper agricultural practises, poor soil conditions and ineffective fungicides have certainly increased the susceptibility of corn to moulds infestation in the field and the consequent mycotoxin production. Among many moulds that can infest corn, Fusarium and Aspergillus moulds have been studied extensively. Fusarium moulds notably produce mycotoxins such as deoxynivalenol (DON), zearalenone (ZEA), T-2 toxin and fumonisins.

Interestingly although the moulds that produce DON and fumonisins belong to the same genus Fusarium, the species within the genus requires different agroclimatic conditions. DON is a major issue in temperate regions of the world, such as North America, Europe, and China, while fumonisins are a major issue in tropical regions such as Asia, South America, and Middle East and Africa (MEA). Such regional demarcation will be lost in importing regions such as Asia and MEA due to the dependence on North America and South America for importing corn.

Contrary to what many people think, Aspergillus fungus can attack corn while it is on the field as well as during storage. Drought conditions and insect damage further increase aflatoxin (AF) contamination in the corn. On the other hand, Penicillium moulds attack corn mainly during improper storage and produce ochratoxins (OTA).

IMPORTANCE OF RAPID TESTS FOR MYCOTOXINS IN CORN
Rapid mycotoxin analysis at the feed mill is an important quality control step used across the globe to make sure purchased corn is of superior quality. To make informed decisions on accepting or rejecting the raw materials, Selko, the feed additive brand of Nutreco, has deployed Mycomaster (rapid mycotoxin analysis tool) at various feed mills across the globe. These systems automatically send the mycotoxin analysis data to Selko’s central database which can be further used to provide customised mycotoxin interpretation reports as well as sharing global insights on periodic mycotoxin threats to livestock and poultry. More than 51,000 samples were analysed in 2022, including 11,728 corn samples. Samples were collected from 42 countries located in the production regions of Europe, North America, Latin America, MEA, and Asia.

GLOBAL MYCOTOXIN CONTAMINATION IN CORN
Mycotoxin contamination levels in corn ranged from 29% to 49% (Table 1). The highest contamination for corn was seen with Fumonisins (57%) followed by ZEA (52%) and AF/DON (49%), while ochratoxin was found least often – in 29% of samples. Toxins with the highest mean concentrations included DON and fumonisins, which averaged 1271ppb and 1629ppb, respectively. However, the median concentration for both contaminants was much lower – 700ppb and 902ppb, respectively – suggesting that some outlier samples with high concentrations could be skewing the analysis. It is recommended, therefore, to present both mean and median values for mycotoxin concentrations. A detailed pictorial mycotoxin distribution can be seen in Figure 1 in the form of a box plot and a jitter. Within the box, the diamond shape represents mean while the centre line of box represents median. The closer the diamond is to the centre line, the more uniform the data.

REGIONAL MYCOTOXIN CONTAMINATION IN CORN
Due to the varied corn growing and storage conditions in different regions of the world, it is important to analyse individual mycotoxin contamination percentages and concentrations by region. Please refer to Table 2 for details.

Aflatoxins. 78% of the corn samples tested in Asia were contaminated with AF followed by Europe and North America (Table 2). The contamination in Asia is expected but that of Europe and North America is a concern. As AF are highly regulated in Europe and North America, such high levels in corn can pose challenges to livestock producers, especially dairy producers, and processors. There has been news in the European market that dairy farmers in recent months have reduced the use of corn and corn by-products in the rations owing to the fear of AF. Concentrations of AF in Asia were much higher than that of other regions, indicating the need for better storage of corn. Transfer of AFB1 from feed to milk is much higher in high-yielding cows and hence AFM1 can be a challenge in Europe despite levels below the recommended median concentrations of 4ppb AFB1 in feed.

Ochratoxins. 100% of the corn samples tested in North America were contaminated with OTA followed by Latin America and MEA (Table 2). In corn, OTA contamination generally happens during storage. In Europe, it is quite common to observe OTA contamination in wheat as Penicillium moulds attack the plant in the field. Such phenomenon is not generally observed in corn. Median concentrations across the globe were quite low and may not be a major concern when considering the individual mycotoxin presence.

Deoxynivalenol (DON). 100% of the corn samples tested in North America were contaminated with DON followed by Latin America and MEA (Table 2). It is not surprising for North America (USA and Canada) as the temperate climate during crop production supports the growth Fusarium graminearum fungal growth. MEA contamination reflects the import of corn from the Americas. In Asia, although the percentage of contamination was low, the mycotoxin concentrations in the positive samples were quite high. The same applies to MEA and Europe. DON is the most common mycotoxin across the globe and concentrations observed in analyses certainly can impact the performance of all species of animals. In recent years, extensive research has been carried out on this mycotoxin looking at its impact on the gut health of livestock and poultry. New regulations on its limits may focus on gut health issues rather than performance impairment.

T-2/HT-2 toxin. 100% of the corn samples tested in North America were contaminated with T-2 toxin followed by Latin America and Europe (Table 2). It is a bit surprising to see such high levels of contamination for North America as this region is not known for high levels of contamination with Fusarium sporotrichoides fungi. Climate change and unexpected weather pattern may be a culprit here. Growing conditions in Latin America and Europe do support the growth of this fungi. Median concentrations indicated here can cause health and production issues except for the concentrations observed in North America. Although Asia observed only 9% contamination with this toxin, median concentrations detected can cause major health and production issues, including mortality in poultry.

Zearalenone. 100% of the corn samples tested in North America were contaminated with ZEA followed by Asia and MEA (Table 2). It is not surprising for North America (USA and Canada) as the temperate climate during crop production supports the growth Fusarium graminearum fungal growth. MEA and Asia contamination levels reflect the import of corn from the Americas. Scientifically it is accepted that DON and ZEA co-occur in corn as both can be produced by Fusarium graminearum. The higher prevalence of ZEA in corn in Asia but not DON poses a question as to whether other storage conditions can promote ZEA production in corn. The concentrations of ZEA found here can cause reproductive issues in sows and cows but are safe to use in other animals.

Fumonisins. 73% of the corn samples tested in Latin America were contaminated with fumonisins followed by Asia and North America (Table 2). It is not surprising to see such contamination as Fusarium proliferatum and Fusarium moniliforme moulds, capable of producing fumonisins, prefer warmer climatic conditions for their growth. Such fungal growth can be further enhanced by drought conditions. Another unique aspect of fumonisins is that these mycotoxins are almost exclusively found in corn and corn by-products. Historically the concentrations of fumonisins found here are not considered a threat to livestock and poultry. But the growing research on their negative effects on gut health and immunity is forcing the scientific community to take another look at their maximum limits in feeds and raw materials.

SEASONAL IMPACT ON MYCOTOXIN CONCENTRATIONS
Mycotoxin concentrations in corn change throughout the year depending on the growing conditions in the field as well as storage conditions. As can be seen in the Figure 2, AF concentrations showed three peaks in the year in the months of February, July, and October. Each one of the mycotoxins showed different peaks indicating the differences in the conditions required for their production. The sizeable quantity of corn produced in 2022 will be used at least until Q1 of 2023 and hence studying such month-to-month variations can provide some tips for effective mycotoxin risk management.

SPECIES RISK ASSESSMENT
Different species have specific sensitivities to mycotoxin exposure and specifically young and reproducing animals can have more severe responses. When evaluating corn and formulating feeds, it is important to consider the types and concentrations of mycotoxins that may be present in corn. For example, corn with higher ZEA can be fed to poultry rather than sows. High concentrations of any mycotoxin in corn should be dealt with cautiously as corn represents more than 50% of most animal diets. It is also important to note that corn is not the only ingredient used in the animal feed. In addition to considering the mycotoxin contribution from corn to the complete feed, the contribution of other ingredients should also be evaluated to understand the total mycotoxin risk. For example, corn DDGS used at low levels of inclusion in poultry feed can contribute to high levels of DON in the complete feed as compared to corn itself.

Last but not least, it is important to realise that most mycotoxins exert additive and synergistic interactions in animals when present in the same feed. The presence of multiple mycotoxins in the corn, hence, need to be dealt with cautiously.

MYCOTOXIN MITIGATION
Feeds contaminated with a range of mycotoxins expose livestock and poultry to multiple challenges threatening various internal organs and systems. For example, the presence of AF, fumonisins and OTA can damage the liver and kidneys and interfere with immune system function, while ZEA interrupts the reproductive system. T2/HT2 toxins and DON damage the gut and immune system functions. All the mycotoxins cannot be managed with the same mitigation strategy. For example, AF respond well to binding agents, while Fumonisins and DON, don’t bond well to agents added to feeds. Mitigation tools must contain multiple modes of action such as a means to reduce the bioavailability of mycotoxins, and ingredients capable of enhancing immunity, gut health, and antioxidant status of animals.

CONCLUSIONS
Undoubtedly corn is the major raw material used in feeds to meet the nutrient demands of livestock and poultry. Despite the efforts from animal scientists and industry professionals, it has not been possible to find a cost-effective alternative to corn. Due to the changing agricultural practices and climate change, mycotoxin contamination in corn is steadily increasing. On top of this, more and more mycotoxins are held responsible for their negative effects on subtle parameters such as gut health, immunity, and antioxidant status. If the future mycotoxin regulations are based on such subtle parameters, mycotoxin limits in animal feeds must come down further. This will certainly put pressure on acceptable limits of mycotoxins in corn. Innovations are needed to improve the overall resilience of animals against a broad range of multiple mycotoxins.

About Dr. Swamy Haladi
Dr. Haladi is the commercial and technical manager for the Mycotoxin Risk Management Programme of Selko Feed Additives. He obtained his Bachelor and Master degrees in veterinary science in India, and then moved to Canada to obtain his PhD in animal and poultry science. During his studies and career, he continued to gain more interest and knowledge in the area of mycotoxins, especially the global challenges around this topic.
He published various articles in both peer-reviewed journals as well as industry magazines and he truly understand the global challenge of mycotoxins. He also developed practical limits for mycotoxins in various species.

About Avinash Bhat
Avinash Bhat has been working for Nutreco and Masterlab since 2017 and has over 20 years of experience in laboratory management and customer service laboratory activities. Currently, he lives in the Netherlands where he works as technical specialist, responsible for mycotoxin analysis at Masterlab.