the research focuses on individual mycotoxins and not their combined toxicity. Regardless of the type of toxin, reduced growth performance and high feed-conversion ratios are of- ten associated with the ingestion of contaminated feeds. Growth might be affected directly, due to lower intakes of contaminated feeds, or indirectly, due to molecular damage at the cellular level. In any case, the final output is the same: reduced growth performance for fish and economic losses for fish farmers. Unfortunately, mycotoxin contamination is a “silent” enemy for farmers, since it is usually not correlated with visual symptoms. Long-term ingestion of feeds with low levels of mycotoxins or acute exposure to high levels might be a reason for the unexplained mortalities that are occasionally observed at fish farms.
The solution To properly manage the mycotoxin risk at the industrial level, it is crucial to examine potential solutions at all of the critical points in the value chain, from field to feed mill. Starting in the field, good agricultural practices such as growing resist- ent crop varieties, crop rotation, soil tillage, and chemical and biological control of plant diseases are recommended. At the pre-harvest stage, mycotoxin contamination cannot be fully prevented, especially during unpredictable weather condi- tions. Raw material suppliers should carry out rapid mycotox- in analyses in cereal products so as to decide whether to ac- cept or reject a batch. Unfortunately, these quick tests can only detect a few toxins and the regulatory limits vary across countries. Thus, the
responsibility for mycotoxin management in aquafeeds is auto matically transferred to the aquafeed producers. At this final stage, mould inhibitors are usually included in feed for- mulations to prevent fungal growth during storage. Mycotoxins produced in the pre-harvest stage are still pres- ent in the feeds and remain almost stable at high tempera- tures during the extrusion process. Feed producers should consider detoxification feeding strategies in order to elimi- nate the negative impacts of mycotoxins on fish after exposure. Among the commercially available detoxification products, enzymes appear to have a high selectivity in trans- forming mycotoxins to less toxic forms. However, this strategy would only be effective if aquafeeds contained just one my- cotoxin. In reality, as mentioned previously, a cocktail of my- cotoxins is likely to be present in feeds and it is not feasible to supplement an enzyme for each potential toxin. As a result, attention is shifting to more practical and universal solutions, such as mycotoxins binders. In general, organic adsorbents bind with a larger spectrum of mycotoxins than the inorganic ones.
Overall, effective mycotoxin management is about seeing the full scope of the challenge, from farm to feed mill and from risk assessment to feed management. The symptoms can be many and varied, but the outcome in all cases will be reduced performance and lost profits. The Alltech Mycotox- in Management team offers a number of solutions to help you mitigate the threat you could face from field and/or storage mycotoxins.
▶ ALL ABOUT FEED | Volume 28, No. 9, 2020 21
The inclusion of plant-based in- gredients in fish diets introduces a potential ex- posure pathway for mycotoxins.
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