Mr Michele Muccio, Product Manager – Mycotoxin Risk Management, BIOMIN Holding GmbH, Austria
The increasing demand for aquaculture products goes hand in hand with a constant increase in prices of animal protein that is pushing feed producers to look at valuable alternatives to meet their needs and contain expenses. According to FAO, the inclusion level of fishmeal in aquafeeds is 25% on average; nevertheless, it accounts for 43% of raw material costs and 32% of total production costs. Alternative proteins (e.g. soybean, wheat and corn gluten), which represent 45% of volume, account for 19% of raw material costs. Therefore, the inclusion of plant protein sources represents an attractive solution to overcome the economic hurdle.
The most common plant ingredients used in aquaculture are wheat, rice bran, soybean meal, different types of cakes, or other commercially available by-products (e.g. dried distillers grains and soluble; DDGS). On one hand, inclusions of plant ingredients may help to reduce the costs of feed production, but on the other hand, they expose producers to new challenges such as lower nutritional value that requires higher inclusion rates, lower palatability, anti-nutritional factors and mycotoxins.
Lower nutritional values of plant-based diets might lead to unbalanced diet formulations that together with the presence of anti-nutritional factors such as non-starch polysaccharides, antigenic compounds, protease inhibitors, etc.; can compromise fish health and consequently production.
Another emerging issue in aquaculture that goes hand in hand with the increasing tendency to include higher ratios of plant-based ingredients in aquafeeds is represented by mycotoxins. These are toxic secondary metabolites produced by certain fungi that contaminate a wide variety of grains and other commodities used in animal and human production. Mycotoxin prevalence changes among different regions, although global trade and climate change have played a role in homogenizing the contamination profile worldwide. Effects of mycotoxins in relevant aquatic species are documented in the literature.
Mycotoxins that have implications for aquaculture-farmed animals are produced by Aspergillus, Penicillium and Fusarium sp. Toxic metabolites produced by these fungi are known to be either carcinogenic (e.g. aflatoxin B1, ochratoxin A, fumonisin B1), oestrogenic (zearalenone), neurotoxic (fumonisin B1), nephrotoxic (ochratoxin), dermatotoxic (trichothecenes). All mycotoxins are immunosuppressive and being feed-borne, they exert negative effects on the gastrointestinal tract, decreasing feed intake, FCR and rendering animals more susceptible to diseases and external stressors such as pathogens.