Mycotoxins are notorious contaminants of animal feed known to exert toxic effects in animals, including aquatic species. Fungi that produce mycotoxins infest crop plants i n the field and agricultural products during storage. Therefore, the inclusion of p lant-based feed ingredients in aquaculture feedstuffs can result in the introduction of mycotoxins. As m ycotoxins are thermostable molecules that resist conditions applied during the feed production process , mycotoxins end up in compound feed. During storage of compound feed for aquaculture in moist and warm conditions, additional mycotoxins may be produced.
Our knowledge of mycotoxin prevalence and impact in the aquaculture sector lags behind what is known about these issues in the terrestrial livestock industry. Therefore, in this study, we investigated mycotoxin occurrence in feedstuffs destined for aquaculture species . To this end , we analyzed mycotoxin concentrations in 273 samples of aquaculture feedstuffs collected in Asia, Africa, Europe and South America.
Materials and Methods
W e collected 273 samples of aquaculture feed from different c ountries in Asia, Africa, Europe and South America and analyzed concentrations of 51 mycotoxins and less-investigated fungal metabolites (“emerging mycotoxins”) using multi-analyte liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods . Analytes included aflatoxins and other Aspergillus mycotoxins, Fusarium mycotoxins (e.g., deoxynivalenol, zearalenone, fumonisins) , Penicillium toxins , ergot alkaloids and Alternaria toxins.
In total, 46 mycotoxins and fungal metabolites were detected in aquaculture feed samples and 97% of the samples were contaminated with at least one mycotoxin/ metabolite. We found that 36 % of the s amples were contaminated with the cancerogenic mycotoxin aflatoxin B1, and 5 % of the samples exceeded the maximum level set for this mycotoxin in fish feed in the European Union (i.e., 10 µg/kg) . Furthermore, Fusarium mycotoxins fumonisins , deoxynivalenol, and zearalenone were prevalent in aquaculture feed samples (detected in 63%, 59 %, and 54%, respectively). In addition, less investigated fungal metabolites such as enniatin B1 (48%), beauvericin (38%), and alternariol (34% ) were frequently detected. Co-contamination of aquaculture feed samples with multiple mycotoxins/metabolites was common. In total , 72% and 36% of the samples were co-contaminated with ≥5 and ≥10 mycotoxins/metabolites, respectively.
M ycotoxins and other, less investigated fungal metabolites we re almost ubiquitously present in aquaculture feedstuffs analyzed in this study. M ycotoxins are known to cause adverse effects in aquatic species such as reduced growth , impaired reproductive performance, increased mortality and immunosuppression. Furthermore, mycotoxins may accumulate in edible tissues. It is therefore necessary to closely monitor mycotoxin concentrations in aquaculture feed and take appropriate measures to minimize their negative impact .
Based on our results, co-contamination of feed with multiple mycotoxins is the rule rather than the ex ception. This finding is not surprising, a s compound feed is a blend of a variety of raw materials , each of which has its own mycotoxin risk profile. Due to toxicological interactions, t hese “cocktails” of mycotoxins in feed can have stronger toxic effects than each individual mycotoxin would have on its own. Our findings underline the necessity to monitor the concentrations of multiple mycotoxins in aquaculture feed simultaneously and to investigate the combined toxicity of mycotoxins in aquaculture species.