EFFECT OF MYCOTOXINS ON INTESTINAL HEALTH

BIŌNTE TECHNICAL DEPARTMENT

Introduction

Mycotoxins are secondary metabolites produced by toxigenic fungi that are frequently found as contaminants of food and feed (Gruber-Dorninger et al., 2019). Among the various effects of these toxins in animals, it is well established that their ingestion can impair intestinal health, which in turn negatively affects overall animal welfare (Liew et al., 2018).

Concept of intestinal health

The gastrointestinal tract is responsible for the digestion and absorption of nutrients, thereby providing energy, but it also represents a fundamental component of the immune system, acting as a protective barrier against infectious and non-infectious agents, such as mycotoxins. In this context, intestinal health is characterised by a state of balance (homeostasis) among the different components of the intestinal barrier, including the microbiota, the mucosa and the immune system. This balance constitutes the basis of animal health, welfare and performance (Celi et al., 2017).

Mycotoxins can disrupt this homeostasis and impair gastrointestinal tract functions, compromising both nutrient absorption and immunological function. In general, mycotoxins exert a direct antimicrobial effect, in addition to a secondary effect derived from the toxicity they induce in intestinal cells, which leads to alterations in the microbiota.

On the other hand, the intestinal microbial population itself can interfere with the absorption and structure of mycotoxins, generating secondary metabolites that may also affect animal health. Thus, a bidirectional interaction between mycotoxins and the intestinal microbiota has been described (Guerre, 2020).

Trichothecenes

Trichothecenes, such as deoxynivalenol or T-2 toxin, have been described as the mycotoxins with the greatest toxicity affecting intestinal health. Trichothecenes decrease the expression of tight junctions and glucose transporters, while simultaneously inducing apoptosis of enterocytes, leading to a reduction in villus height. Consequently, they increase intestinal permeability and reduce nutrient absorption. These mycotoxins also reduce the number of goblet cells—mucin-secreting cells with an important protective function—as well as cytokine production. In addition, they induce the release of satiety hormones, compromising productive parameters and leading to oxidative stress and hepatic damage. In summary, trichothecenes negatively affect intestinal absorption, integrity, and immunity.

Fumonisins

Fumonisins reduce the expression of tight junctions and induce intestinal epithelial cell apoptosis (due to sphinganine accumulation), thereby increasing intestinal permeability and enabling bacterial translocation into the bloodstream. In contrast to trichothecenes, fumonisins stimulate continuous mucin hypersecretion by goblet cells, leading to their exhaustion and compromising the integrity of the mucosal barrier.

In conclusion, these mycotoxins impair immune function by disrupting the intestinal barrier, rendering animals more susceptible to secondary infections.

Ochratoxin A

Ochratoxin A is among the most common mycotoxins in animal production and, although the kidney is its primary target organ, it also exerts negative effects on the gastrointestinal tract. This toxin increases intestinal permeability by reducing the expression of tight junctions and inducing oxidative stress, which in turn leads to enterocyte apoptosis. Therefore, intestinal villus height is reduced. In parallel, immune function is impaired due to a decrease in cytokine expression.

Aflatoxins

Aflatoxins, among which aflatoxin B1 is the most relevant, have the liver as their primary target organ. These mycotoxins are characterised by marked hepatotoxicity and by their ability to compromise productive performance and immune function. However, their toxicity at the level of the gastrointestinal tract is comparable to that of other mycotoxins. They increase intestinal permeability and induce degeneration of the intestinal morphological structure, while also altering immune function by increasing the infiltration of leukocytes and lymphocytes in the intestinal mucosa.

Zearalenone

The effects of zearalenone on the gastrointestinal tract are considered less detrimental compared with those of other mycotoxins. Indeed, differences have been reported between the toxicity of zearalenone and that of its metabolites; however, in both cases, the reproductive system remains the primary target organ.

Conclusion

When addressing mycotoxin contamination, it is important to consider that the most frequent scenario involves multi-contamination. In this context, the different mycotoxins present in feed may interact with one another, giving rise to synergistic and additive effects. Consequently, the consumption of such feeds can lead to alterations of the gastrointestinal barrier in animals, which may result in immunosuppression and compromise both animal health and productive performance.

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