How do mycotoxins challenge shrimp robustness?

Nutritional requirements and major feed ingredients

Like all living animals, shrimp have a requirement for certain nutrients, including amino-acids, cholesterol, vitamins, and minerals. Although dietary formulations vary depending on raw material availability, price, and developmental stage, typically one can expect 25 - >40% crude protein, 6-12% crude lipid ₍₂₎ as well as essential micro-nutrients. For vitamin recommendations, dsm-firmenich has developed Optimum Vitamin Nutrition® guidelines. An example of a typical shrimp diet is given in Table 1.

From a macro-ingredient perspective, shrimp feeds are following the global trend to reduce reliance on marine ingredients, often through increased usage of plant-based raw materials.

Plant proteins, while they can significantly boost overall protein content, come with potential drawbacks. Even when diets are carefully balanced to address amino acid limitations, incorporating more plant-based ingredients raises the risk of introducing undesirable contaminants, which can adversely affect the health and performance of shrimp. These contaminants may consist of anti-nutritional factors (ANFs), such as mycotoxins.

Effects of mycotoxins in shrimp

Although mycotoxin effects have been extensively investigated in land-based animals, there is a notable scarcity of research, particularly in the context of aquaculture, specifically regarding shrimp. Unlike terrestrial animals, aquatic species seldom exhibit obvious clinical symptoms as a result of mycotoxin contamination. Instead, they are more commonly subjected to prolonged exposure to moderate levels of mycotoxins, which is known as chronic exposure. This chronic exposure can lead to non-specific consequences, such as reduced performance (slower growth, higher feed conversion ratios), increased susceptibility to diseases, and elevated healthcare costs. However, these subtle effects are often overlooked or not attributed to the presence of mycotoxins.

Effects of mycotoxins on hepatopancreas

The hepatopancreas is the main site for nutrient metabolism and detoxification of xenobiotics in crustaceans. Several studies show detrimental effects of mycotoxins on this organ as changes in histology or lesions (Table 2). Detrimental effects on this organ may influence nutrient metabolism and decrease energy of animals to gain weight and deal with other stress factors. The hepatopancreas is the site of hemocyte production, maturation, specialization, and release. Immunologic function in shrimp largely relies on the activity of these hemocytes: cells carrying out numerous functions including phagocytosis and recognition of pathogens. If the health of the hepatopancreas is compromised so might be the immune system ₍₃₎.

In shrimps, most studies have been conducted with Afla B1, the most toxic and carcinogenic mycotoxin.

Effects of mycotoxins on intestine

The shrimp intestine is an important part of the immune system as the first barrier between the body and toxic entities. Peer-reviewed publications show that several mycotoxins do impact intestinal structure and immune system. Some recent studies focused on the expression of genes important for the immune system, and immune regulation. Table 3 gives a summary of the observed effects.

Changes in the intestinal epithelial cells (as shown for e.g. DON and T-2 toxin) might negatively affect nutrient absorption and thus wellbeing and performance of shrimp.

Effects of mycotoxins on product quality

With all these results showing negative effects on the hepatopancreas, intestine, performance, and probably immune system, let`s not forget about final product quality. Possible residues of Afla in shrimp need further exploration (₍₈₎: found residues in hepatopancreas but not muscle). One study indicated a possible impact of FUM (fumonisins )-contaminated diet on shrimp muscle texture, which might affect consumer acceptance.

Importance of Mycotoxin Risk Management

The risk of mycotoxin contamination is never zero! Even with the best quality control procedures, mycotoxins are a constant threat, and therefore a robust mycotoxin risk management program is essential. Part of this is using a mycotoxin deactivator in the feed formulation. Mycofix® is a state-of-the-art mycotoxin deactivator comprising three modes of action for the ultimate insurance policy against a wide range of known, and emerging mycotoxins. Adsorption to bind adsorbable mycotoxins, biotransformation to detoxify non-adsorbable mycotoxins and bioprotection, natural ingredients supporting hepatopancreas, immune system and intestinal barrier.

An in-house trial was performed with white-leg shrimp (initial weight of ~1.325g) over 8 weeks. Survival and performance were evaluated in comparison to a group with the same moderately contaminated diet but also the inclusion (2.5 kg/t) of Mycofix® PRO-tect (combining the adsorption and bioprotection component). Feed was analyzed with the multi-mycotoxin method Spectrum 380®, the most comprehensive analysis method available covering >800 different mycotoxins and fungal/plant- and bacterial metabolites, developed and performed at the University of Natural Resources and Life Sciences (Vienna/Tulln). The feed showed only moderate natural contamination levels of mycotoxins and emerging mycotoxins (DON 12ppb, ZEN 13 ppb, Beauvericin 2.8ppb, Enniatin B 1.6ppb and Enniatin B1 2.7 ppb as well as moderate levels of other Fusarium metabolites) (see Table 4).