Mycotoxin insights in shrimp feed 2023

In 2020, Pacific white shrimp, alternatively known as Litopenaeus vannamei, emerged as the most popular seafood, with a production volume of 5.8 million tonnes. This accounts for 12% of total aquaculture output, as reported by the Food and Agriculture Organization (FAO) in 2022. The global shrimp farming industry relies heavily on intensive operations primarily situated in East and Southeast Asia and in Latin America, serving lucrative markets in North America, Europe and Japan.

An ever-changing feeding landscape

Shrimp have historically required diets rich in protein, primarily sourced from fishmeal obtained from wild-caught, low-trophic fish species. However, with the increase in prices and the limited availability of fishmeal, extensive research has been dedicated to what to feed shrimp. This means exploring alternative sources of protein, including those from plants, animals and single-cell protein sources (Chen et al. 2023).

Over the past two decades, plant-based protein sources have gained prominence in commercial shrimp feed formulations as substitutes for fishmeal. These plant-based substitutes encompass a range of meal options, such as soybean meal, cottonseed meal, rapeseed meal, peanut meal and sunflower meal. Additionally, cereals like wheat, corn, barley and their byproducts, including corn gluten and wheat bran as well as distillers’ dried grains (DDGs), have been incorporated into shrimp diets.

The increasing use of plant-based ingredients in aquafeed, including for shrimp feed, comes with certain nutritional challenges. These challenges encompass amino acid deficiencies, issues related to palatability, reduced digestibility, and the presence of anti-nutritional factors. Furthermore, the elevated inclusion of plant-based ingredients has raised concern about the potential introduction of mycotoxins into the final feeds, which would pose a significant issue for feed safety within the aquaculture industry.

Mycotoxins are toxic compounds produced by fungi. They can contaminate crops before or after harvest, depending on prevailing temperatures and humidity levels. These mycotoxins can ultimately find their way into the ingredients and final feeds used in aquaculture.

A 2021 study (Koletsi et al.) shed light on the prevalence of mycotoxins in raw materials and aquafeed samples from 2012–2019. The analysis was carried out using liquid chromatography- tandem mass spectrometry (LC-MS/MS) at an Alltech 37+® lab. Of the tested wheat samples, 80% tested positive for at least one mycotoxin, with 63% showing the presence of multiple mycotoxins. Similarly, 93% of corn samples analyzed contained at least one mycotoxin, with 88% exhibiting the presence of multiple mycotoxins. Soybean meal was not exempt from these findings, as 87% of samples tested positive for at least one mycotoxin, with 75% containing multiple mycotoxins.

Presence of mycotoxins in shrimp feed ingredients

Now we present an update on mycotoxin profiles from 2023 detected in commonly used plant-based ingredients in shrimp feeds, namely soybean meal (n=85), DDGs (n=63), wheat (n=109), corn (n=247), and byproducts such as wheat bran and corn gluten (n=23). These samples, sourced from around the world, were submitted to the Alltech 37+ lab for analysis between January and June of 2023. Using LC-MS/MS, the lab was able to detect up to 54 mycotoxins. The results, which are detailed in Table 1, reveal that regardless of the ingredient, all samples tested positive for at least one mycotoxin, with most showing co-occurrence of multiple mycotoxins within the same sample. Mycotoxin groups with occurrence rates above 10% are presented in the table for reference.

Table 1: The most frequent mycotoxin groups (occurrence > 10%) in plant-based ingredients commonly used in shrimp feeds, with their average and maximum levels (ppb)

What is apparent in Table 1 is the high occurrence of “emerging mycotoxins” in all tested ingredients, with frequencies ranging from 94% to 100%. These mycotoxins, neither routinely detected on-farm nor legislatively regulated, are on the rise. Corn, often a key component in shrimp feeds, had the highest average and maximum concentration of emerging mycotoxins (254.4 ppb and 4,751 ppb, respectively) This is not surprising  considering the absence of regulatory limits for these toxins.

Additionally, other mycotoxin groups, like fusaric acid, fumonisins, type B trichothecenes, type A trichothecenes, and zearalenone were also highly prevalent in the tested feed ingredients. For example, in corn, the levels of type A and type b trichothecenes exceeded recommended limits for cereals intended for animal feeds.

Risk quantification in shrimp feeds

To estimate the total risk of mycotoxin contamination in shrimp feeds, we employed the Alltech® DIET™ Estimator tool. This factors in the inclusion rates of plant-based ingredients and the mycotoxin contamination data. The risk was assessed using a shrimp feed recipe from the Practical Aquaculture Feed Formulation Database (PAFF) and mycotoxin results from the first half of 2023. The resulting Alltech risk equivalent quantity (REQ) was measured at 10.4 ppb, considered moderate for shrimp.

The inclusion rates of ingredients matter significantly in calculating overall contamination risk. Shrimp formulations from Southeast Asia and Latin America exhibited varying levels of risk, with Latin American diets showing a higher risk due to the inclusion of corn.

Figure 1. Estimation of REQ based on the inclusion level of plant-based ingredients used in a shrimp feed

Mycotoxins’ impact on productivity and health

Shrimp farms, particularly in tropical areas, provide ideal conditions for Aspergillus fungi, raising concerns about aflatoxin B1 contamination. Research indicates that aflatoxin B1 levels above 1 mg/kg adversely affect shrimp survival rates, growth and tissue health.

Other mycotoxins, such as deoxynivalenol (DON), T-2 toxins, and fumonisin B1, can also have severe consequences. High levels of DON impair growth and weaken the shrimp’s immune response, while T-2 toxins induce oxidative stress and damage various physiological aspects. Fumonisin B1 has been shown to reduce growth, muscle protein concentration and immune response, affecting both the shrimp’s texture and consumer acceptability.

The co-occurrence of multiple mycotoxins in plant-based ingredients is a concern. While in vitro studies hint at synergistic effects, the full impact of mycotoxin occurrence on shrimp remains unknown. Emerging mycotoxins and fusaric acid, though prevalent, lack regulatory limits and research on their effects on shrimp.

The findings emphasize the urgent need for a holistic mycotoxin management approach in the shrimp farming industry. Without effective strategies to mitigate the risks, both shrimp health and the industry’s economic stability are at stake.

To learn more about the tools and technologies offered by the Alltech Mycotoxin Management program, visit knowmycotoxins.com.

To recognize the signs of mycotoxin exposure in shrimp, click here.

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