Tony McDougall (journalist) once wrote in Poultry World magazine: “Increasing demand for eggs, meat and milk in recent decades has increased the EU’s imports of cereals and pulses from developing countries with more tropical climates, where mycotoxin levels are higher – and therefore increased the prevalence of mycotoxins in the EU.”
In the livestock industry, mycotoxins are emerging as silent threats, often hidden in animal feed. These toxic substances, produced by fungi, can contaminate a variety of crops, including grains such as corn and wheat. Their presence is particularly common in warm, humid climates, where conditions are favorable for the growth of fungi.
As a result, livestock farms in such areas face increased risks of mycotoxin contamination, which can compromise animal health and growth.
What are mycotoxins?
Mycotoxins, which are toxic secondary metabolites produced by various fungal species, are commonly found contaminating food and animal feed. Often, a single fungal species may produce multiple mycotoxins simultaneously, while different fungi can also multiply on the same plant, resulting in the simultaneous occurrence of multiple mycotoxins. These fungi attack the crop and produce mycotoxins during its growth, as well as during storage and transportation processes.
Types and sources of mycotoxins
Among the most important mycotoxins identified in animal feed are aflatoxin B1 (AFB1), ochratoxin A (OTA), fumonisin B1 (FB1), deoxynivalenol (DON), T-2 and HT-2 toxins, and zearalenone (ZEN). In addition, emerging mycotoxins such as bevorysin (BEA) and enyatins (ENNs) have been identified in food commodities. However, the discussion of these toxins is limited due to the lack of monitoring measures and accurate measurements.
The presence of mycotoxins in the animal feed chain is primarily due to fungal infections in agricultural products and the use of mold-contaminated grains and forages in animal feed formulations. This contamination poses significant risks to animal health and general condition, highlighting the urgent need for effective management strategies to reduce mycotoxin exposure in animal diets.
Aflatoxin
Aflatoxins (AFs) originate from fungi of the genus Aspergillus, mainly Aspergillus flavus and Aspergillus parasiticus, and produce four main types: AFB1, AFB2, AFG1, and AFG2. AFB1, which is known as a highly toxic mycotoxin, is particularly known as a potent hepatocarcinogen.
AFs are classified by the International Agency for Research on Cancer (IARC) as carcinogenic to humans (Group 1). Their entry into the human food chain occurs through direct consumption of contaminated agricultural products or processed foods and indirectly through animal products derived from animals fed AF-contaminated feed.
This contamination, especially when AFB1 is present in the feed consumed by dairy cows, can lead to various symptoms and pose serious risks to human health through the metabolism of AFB1 to AFM1, which is excreted in milk.
Deoxynivalenol (DON)
Deoxynivalenol (DON), also known as vomitoxin, is a trichothecene mycotoxin produced primarily by Fusarium graminarum and commonly found in cereals such as wheat, corn, barley, and their by-products. The toxin significantly affects monogastric animals, particularly pigs and poultry, through contaminated feed. Pigs are more susceptible to DON due to their wheat-heavy diets, and after contamination, their feed intake and weight gain decrease. This toxin also impairs the growth, immune response, and reproductive performance of pigs. Although poultry are affected by DON, their sensitivity differs due to metabolic differences. The adverse effects on poultry growth are not consistent; low concentrations cause reduced feed intake, and higher doses lead to gastrointestinal lesions, especially in the duodenum and jejunum.
Zearalenone (ZEA)
Zearalenone (ZEA) is a mycotoxin produced by various Fusarium fungal species, commonly found in cereals such as corn, wheat, barley, and oats. It is structurally similar to estrogen and is classified as an estrogenic mycotoxin. ZEA can contaminate animal feed and, through it, human food, posing health risks to both livestock and humans. In animals, ZEA consumption can lead to reproductive problems, including increased estrogen and infertility, especially in pigs. Due to its estrogenic properties, ZEA exposure in humans has been associated with hormonal disruptions and adverse reproductive effects. Effective management strategies to mitigate ZEA contamination are crucial to ensure food and feed safety.
Fumonisins
Fumonisins (FBs), commonly classified as Fusarium toxins, are produced by various species of the genus Fusarium, particularly F. verticillioides and F. proliferatum. The main toxins include FB1, FB2, FB3, and FB4, with FB1 being recognized as the most common and toxic. FBs, classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen (Group 2B), disrupt sphingolipid biosynthesis rather than causing direct DNA damage, due to their structural similarities to sphingolipid precursors. EU guidance levels set total FB1 and FB2 at up to 60000 µg/kg in maize and maize products for food materials, and vary from 5000 µg/kg to 50000 µg/kg for complete feed and supplements, depending on the animal species and age.
Ochratoxin A (OTA)
Ochratoxins are primarily produced by Aspergillus ochraceus (A. ochraceus), but other Aspergillus species like A. carbonarius and Penicillium species such as P. verrucosum and P. nordicum can also produce them. Meanwhile, Ochratoxin A (OTA), a potent nephrotoxin, causes kidney toxicity and is associated with carcinogenic, teratogenic, immunotoxic, and neurotoxic effects. It is linked to Balkan endemic nephropathy and is classified by the International Agency for Research on Cancer (IARC) as possibly carcinogenic to humans (Group 2B). The presence of OTA in animal-derived products like meat and meat by-products is a significant public health concern and requires close monitoring to minimize risks to humans.
Effects of Mycotoxins on Livestock
Cattle
Mycotoxins pose significant health risks to livestock, affecting their well-being across various species. In cattle, exposure to mycotoxins can lead to reduced feed intake, impaired growth rates, decreased milk production, and compromised immune function. Additionally, mycotoxins disrupt rumen fermentation, impacting nutrient absorption and overall digestive health. This can cause digestive disorders such as diarrhea and acidosis, exacerbating the animal’s condition and potentially leading to economic losses for farmers.
Swine
Swine are particularly susceptible to mycotoxins, especially toxins like deoxynivalenol (DON) and zearalenone (ZEN), which cause reproductive problems such as reduced fertility, embryonic loss, and abnormal development of reproductive organs. Mycotoxin-contaminated feed also leads to decreased weight gain, poor feed conversion efficiency, and increased susceptibility to infections in pigs. Furthermore, chronic exposure to mycotoxins can cause liver and kidney damage, negatively impacting the overall health and longevity of swine herds.
Mycotoxin Detection and Monitoring
Mycotoxin detection and monitoring are crucial for ensuring food and feed safety. Currently, various methods are used for mycotoxin detection, including enzyme-linked immunosorbent assays (ELISA), chromatographic techniques such as high-performance liquid chromatography (HPLC), and molecular methods like polymerase chain reaction (PCR). These methods offer high sensitivity and specificity, allowing for accurate determination of mycotoxins in complex matrices. Rapid screening assays provide quick results, enabling timely intervention to prevent mycotoxin exposure in livestock and humans. Continuous monitoring of feed ingredients and finished feed batches is essential for effective mycotoxin contamination detection and mitigation, ensuring the health and safety of animals and consumers.
Management Strategies and Preventive Measures
In response to the growing concern about mycotoxin contamination, scientists and the animal feed industry are actively focusing on developing strategies to combat these harmful substances. This article focuses on recent advances in the detoxification of common mycotoxins in animal feed. This report includes research articles and reviews that explore various approaches, such as the use of new materials or microorganisms for mycotoxin biodegradation, the use of modified adsorbents to reduce mycotoxin toxicity, the implementation of nutritional strategies to reduce mycotoxicosis, and understanding the mechanisms of mycotoxin toxicity to inform the increased use of antidotes.
Method One
Novel Adsorbents: Efforts to reduce mycotoxin contamination include the use of adsorbent materials. For example, scientists have developed novel adsorbents that effectively bind mycotoxins. These adsorbents, including nanoparticles and carbon nanotubes, help reduce mycotoxin levels in feed by binding to the toxins, although they do not directly affect fungal activity.
Method Two
Biological Methods: Biological methods include various strategies, such as enzymatic degradation and microbial adsorption, to combat mycotoxin contamination. Some bacteria and fungi are capable of degrading or removing mycotoxins, and enzymes like TF301 play a role in their degradation.
Conclusion
Mycotoxin contamination poses significant risks to animal health and growth, highlighting the need for effective management strategies. Proper and timely disinfection of animal rearing environments and feed storage, as well as the use of high-quality feed, can largely prevent the spread and increase of the destructive effects of mycotoxins.
