Occurrence of Fungi and Mycotoxins in Fish Feeds and Their Impact on Fish Health

Abstract

The rapid population growth in developing countries has led to strong pressure on capture fisheries. However, capture fisheries have reached their maximal limits of fish production and are supplemented by farmed fish. The growth in aquaculture has led to high demand for fish feeds, which play a very important role in fish nutrition and health. Use of animal protein in fish feeds is expensive; hence, a majority of farmers from developing countries use local feed ingredients from plant origin as a source of dietary protein. However, these ingredients of plant origin provide the best natural substrates for fungi, which can be easily accompanied by mycotoxin development under suitable conditions. The locally made feed comprises ingredients such as soybeans, cottonseed cake, and wheat and maize bran which are mixed together and ground after which the compounded feed is pelleted and stored. Among the ingredients, maize and oilseeds are more susceptible for mycotoxigenic fungi compared to other ingredients. The outcomes of mycotoxin contamination in fish feeds are not different from other animal species intended for human consumption, and they are directly associated with production losses, particularly decreased weight gain and feed conversion, impaired immune system and reproductive performance, and increased fish mortality. Fish may also carry mycotoxin residues along the food chain, thus compromising human health. Hence, it is important to ensure the control of mycotoxin contamination in fish feeds, especially during the production and storage.

Co-Occurrence and Levels of Mycotoxins in Fish Feeds in Kenya

“…Previous studies have confirmed the occurrence of various mycotoxins in different animal feeds and feed ingredients in Kenya [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. However, of greatest emphasis have been aflatoxins which are highly prevalent in Kenya with the most recent severe epidemic that killed 125 people being reported in the year 2004 [ 35 , 36 ].…”

Occurrence of Mycotoxins in Fish Feed and Its Effects: A Review

“…The trend to use plant-based materials in aquafeeds appears to be increasing [23]. However, contamination of these ingredients with potentially mycotoxinogenic fungi, particularly Aspergillus flavus and Aspergillus parasiticus, is frequent and occurs virtually everywhere [40]. In Serbia, zearalenone, ochratoxin A and aflatoxin B 1 were detected in corn, wheat and barley destined for fish feed production.…”

“…Apart from being a carcinogen, it also has genotoxic and immunodulatory effects on animals and humans. Overall, exposure of aflatoxin B 1 results in poor growth, anemia, impaired blood clotting, sensitivity to bruising, damage to the liver and other organs, decreased immune responsiveness resulting in an increased vulnerability to bacteria, viral or parasitic infections, and increased mortality [40,70]. The in vivo effects on fish of aflatoxins and sterigmatocystin are described in Table 1.…”

“…Clinical signs associated with aflatoxicosis in fish include pale gills, impaired blood clotting, poor growth rates and lack of weight gain [61]. Visible signs of severe infection might be reduced survival rate, darkening/yellowing of the body and abnormal behavior, as seen in Nile tilapia and juvenile sturgeon [40,71,72].…”

“…The LD 50 calculated for Nile tilapia was 1.0 and 1.3 mg/kg of bodyweight to aflatoxin B 1 [77]. However, the intake of up to 3.0 mg/kg of aflatoxin B 1 seems to not affect the survival rate of these fish [40,[78][79][80]. The effects of aflatoxin B 1 are, however, dose-and duration-dependent [78].…”