MYCOTOXINS HOW DO THEY GET INTO AQUAFEED?
Dr. Rui Alexandre Gonçalves Aquaculture and Mycotoxin Expert Aquaculture Business Developer – Lucta S.A. Innovation Division – Feed Additives UAB Research Park, Bellaterra, Barcelona, Spain
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The awareness of mycotoxin-related
Mycotoxins are secondary metabolites
issues in the aquaculture industry has
produced by some molds (Hussein and Brasel,
been increasing, accentuated by the
2001). They are commonly reported to appear in agricultural commodities (pre-and/ or post-harvest), including finished feeds.
replacement of marine ingredients (Gonçalves
et al., 2018; Tacon et al., 2011).
Traditionally, the use of minor amounts
Chemically, mycotoxins have low molecular
of plant feedstuffs led to a general
weight, displaying a wide range of structures
perception that mycotoxins were not a
(Mallmann and Dilkin, 2007). This variability
relevant issue in aquaculture and that
is responsible for the diverse biological
the majority of mycotoxin-related issues
effects produced by mycotoxins.
would only arise due to poor storage conditions, i.e., aflatoxin contamination, but this is not entirely true.
CARCINOGENICITY ZEARALEONE
ESTROGENICITY AFLATOXIN B1
EXAMPLES OF MYCOTOXIN-INDUCED BIOLOGICAL EFFECTS
NEPHROTOXICITY NEUROTOXICITY
FUMONISIN B1
OCHRATOXIN A
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Despite being identified as categorically undesirable for most animal species, the
Not all plant meals are the same!
occurrence of mycotoxins, at least in field conditions, is not completely preventable even when using good manufacturing practices.
As mycotoxins are mainly found in agricultural
The difficulty in understanding the risk of mycotoxin contamination in aquaculture finished feeds is related to the diversity of aquaculture species. For most species, the selection of plant meals depends on a combination of factors (Davis y Sookying, 2009; Gatlin et al., 2007; Krogdahl et al., 2010): Local market availability.
commodities, the tendency to replace animal-derived proteins, such as fish meal, with plant protein sources has increased the risk of mycotoxin contamination in aquaculture feeds.
Cost. The protein meal’s nutritional profile (anti-nutritional factor content and levels).
Generally, plant-based meals are known for their natural profile of anti-nutritional
However, depending on the species and
factors (ANF’s), such as cyanogens,
production region, evaluating mycotoxin
saponins, tannins, etc., that are harmful to
contamination may not be a common
fish and shrimp (Krogdahl et al., 2010).
practice in the aquaculture industry, so it becomes difficult to understand
Although there are processes that aid
the contamination risk of certain plant
in the removal or inactivation of many
commodities, especially the ones used locally.
of these ANF’s, the same does not apply to mycotoxins, as they are highly stable when subjected to processing conditions (e.g., high temperature and pressure) (Cheli et al., 2013).
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Moreover, climate change and world commodities trade also contribute to the difficulty in predicting the risk of mycotoxin contamination in aquaculture finished feeds.
In some countries, mycotoxin contamination is considered a strictly seasonal issue. However, the increasing globalization of trade and incorporation of imported raw materials in aquafeeds exposes the industry to the risk of mycotoxins that may not be common for the region.
When plant meals get too expensive The increasing cost and sustainability concerns on the use of marine ingredients for aquaculture feeds have encouraged the use of plant proteins. However, recently, the cost of plant-based raw materials has begun to rise, partly due to the increased demand for human and livestock species consumption and production challenges associated with the sustainability of certain plant commodities. As a consequence, the volume and quality of affordable plant materials available for animal feed has fallen. Aquaculture feed manufacturers are now faced with either increasing the price of aquaculture feeds or trying to use alternative sources of plant meals.
Economic pressures can lead to the use of lower quality raw materials which may increase the risk of contamination with one or more mycotoxins.
Alternatively, by-products and processed ingredients could be used but they are known to have increased levels of mycotoxins since most of mycotoxins are not destroyed during commodity or feed processing (Gonçalves et al., 2017). These mycotoxins can also be redistributed and concentrated in certain milling fractions.
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Consequences of limited availability of plant materials for aquafeed
Cost Volume & quality of raw materials
Aquaculture feed price
Inclusion of alternative sources of plant meals, by-products and processed ingredients
The lack of legislation regarding mycotoxin contamination for aquaculture species also leaves some room for aquafeed manufacturers to use feedstuffs that have been rejected by the livestock sector because of mycotoxin contamination and stricter regulation.
The contamination of aquafeeds and plant-based feedstuffs with mycotoxins is, in general, often neglected. Currently, there is a growing knowledge regarding mycotoxin contamination in aquafeeds and ingredients destined to be used in fish and shrimp feeds (Gonçalves et al., 2016; Gonçalves et al., 2017).
However, several gaps on how to improve and address mycotoxin risk management in aquaculture still remain.
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Awareness of mycotoxin-related issues in the aquaculture industry The awareness of mycotoxin-related issues in the industry has grown as feed manufacturers
This was shown by Gonçalves et al.,
and producers realize the importance of
(2017), who reported that in Asian samples, soybean meal, wheat, wheat bran, corn, corn gluten meal, rapeseed/canola meal, and rice bran were mainly contaminated with Fusarium (ZEN, DON and FB).
mycotoxins and their potential to impact animal production. However, the idea that the majority of mycotoxin-related issues are a result of poor on-farm storage conditions leading to aflatoxin contamination is still deeply entrenched across the aquaculture industry.
The only exception was cottonseed meal, which was mainly contaminated with AF and Fusarium While it remains true that poor storage
toxins (ZEN and DON) in considerable amounts.
conditions can promote the growth of Aspergillus sp. and Penicillium sp.,ultimately leading to
Finished feed samples were also mainly
the production of aflatoxins and ochratoxin
contaminated with Fusarium mycotoxins,
A, the reality is that most of the mycotoxins
reflecting the use of plant meals.
found in finished feeds come from the raw materials used to produce them. Results shown by Gonçalves et al., (2017) confirm that mycotoxin contamination found in finished feeds is mostly related to the plant-based raw materials used in their formulation, since Fusarium fungi are generally found in field samples rather than in storage samples.
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The mycotoxin risk of less typical commodities should not be ignored! As mentioned before, mycotoxins are mainly
Shrimp head constitutes 34 to 45% of
found in agricultural commodities. However,
the whole shrimp, being shrimp head
other commodities may also be contaminated
meal (SHM) an important by-product
with mycotoxins and should not be ignored.
of the shrimp industry. A possible SHM contamination with mycotoxins (at storage or by bio-accumulation) could represent
Theoretically, under suitable conditions, any
a big constraint for the industry..
commodity may be a good substrate for fungal growth and mycotoxin production. Shrimp meal can be manufactured by drying the material directly under the sun or in an In reality, little attention is given to other
oven (Hertrampf and Piedad-Pascual, 2000).
commodities besides agricultural commodities. Considering that production However, in the case of aquaculture,
is normally done in small
aquatic by-products (both from fisheries and
lots of sun-dried fish under
aquaculture) represent a significant inclusion
different conditions, a certain
level in aquafeed formulations. Therefore,
variation in the quality of the
their possible contribution to mycotoxin
commodity can be expected.
contamination should be also investigated.
For example, shrimp head meal is an important by-product of the shrimp industry.
While not being a typical product to analyze for the presence of mycotoxins, it is known that their presence is possible
This is especially true in the case of mycotoxins such as AF and OTA, as they are produced by Aspergillus sp. and Penicillium sp. species that proliferate under inadequate storage conditions.
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While it is easy to understand the possible contamination of aquatic by-products with AF and OTA, as they are storage mycotoxins, it is harder to fully explain the presence of less common toxins produced by Fusarium molds that are generally associated with field conditions rather than storage.
However, Fegan and Spring (2007) reported several marine-derived samples from fishmeal to shrimp meal were contaminated with mycotoxins produced by Fusarium sp. (N=5, origin Asia; T-2=
The capacity of F. oxysporum or F. solani to produce toxins is unknown, but the possibility of having aquatic Fusarium strains producing these mycotoxins cannot be totally rejected and this hypothesis needs to be further investigated.
Another possibility for the presence of Fusarium toxins in these aquatic by-products may be due to their bioaccumulation and to the fact that they are not destroyed during processing.
60.186 ppb and ZEA= 72.036 ppb). However, the topic of mycotoxin Later on, Gonçalves et al. (2017) sourced
bioaccumulation in aquaculture products is
samples of dried fish and shrimp head
little documented (Gonçalves et al., 2020).
meal (SHM) contaminated with fumonisins (N=2; Origin: Thailand; FB1 + FB2; dried fish= 64 ppb; SHM= 24 ppb).
In reality, is difficult to fully understand the origin of Fusarium mycotoxins in marine-derived byproducts. Some Fusarium strains, namely F. oxysporum and F. solani,are known and well described as opportunistic pathogens for fish and shrimp (Hatai et al., 1986; Lightner, 1996; Ostland et al., 1987; Souheil et al., 1999).
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Some take-home messages Despite the efforts to control fungal
Mycotoxins occurring in plant commodities
contamination, both in the field and in
and/or aquatic by-products are not destroyed
storage, extensive mycotoxin contamination
during most processing operations.
has been reported in commodities and finished feeds. The type and prevalence of mycotoxin contamination depend on:
On the contrary, processing affects the distribution of mycotoxins, concentrating them into fractions
The type of substrate (plant meal type
that are commonly used in animal feed (plant
and finished feed characteristics).
by-products; e.g., corn gluten meal, DDGS, etc.).
The geographical area. The fate of mycotoxins during cereal processing Seasonal and local weather
(sorting, cleaning, milling, and thermal processes) has
conditions during critical plant
been studied by several authors. However, their level in
growth stages or storage.
feedstuffs is variable and affected by several factors: The type of mycotoxins.
Besides agriculture commodities, the risk of mycotoxin contamination in other aquatic
The level and extent of fungal contamination.
by-products should not be ignored. Despite being less characterized when compared to
The complexity of the cereal-processing technology.
agricultural commodities, some scientific pieces of evidence point to these commodities as a possible source of mycotoxins.
Factors contributing to the presence or production of mycotoxins include environmental (temperature, humidity) and ecological conditions (insect attacks, physical plant damage, and general stress). However, these factors are oftentimes beyond human control.
It is recommended that aquafeed and aquaculture producers regularly monitor raw commodity feed ingredients and finished feeds for mycotoxin contamination, either through on-site rapid testing or through an external laboratory that may be equipped with more powerful detection equipment. In cases where feed quality has been compromised by mycotoxins, the use of a mycotoxin deactivator is advised.
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