Wednesday, January 16, 2019

Fumonisins in aquaculture: The most sensitive species

by Rui A Gonçalves, Biomin Holding, Austria

In aquaculture, fumonisins (FUM) have generally been associated with reduced growth rate, feed consumption and feed efficiency, and impaired sphingolipid metabolism.

Fumonisin toxicity is related to this ability to inhibit sphinganine (sphingosine) N-acyltransferase (ceramide synthase), a key enzyme in lipid metabolism, disrupting this pathway. This is due to the long-chain hydrocarbon unit (similar to that of sphingosine and sphinganine) in these mycotoxins, which plays a role in their toxicity.
 


Sensitivity of freshwater species
Little information is available on the effects of fumonisins on aquaculture species, and most research focuses on freshwater species.

The channel catfish (Ictalurus punctatus) is the most widely studied species. According to authors, such as Goel, Li and Lumbertdacha, these fish can tolerate relatively high levels of FUM, with a sensitivity level of around 10 mg fumonisin B1 (FB1)/kg feed. Adverse effects of fumonisin-contaminated diets have also been reported in carp (Cyprinus carpio L.): various experiments have observed scattered lesions in the exocrine and endocrine pancreas, and interrenal tissue, probably due to ischemia and/or increased endothelial permeability.

In another study by Pepeljnjak, one-year-old carp were fed pellets containing 500, 5,000 or 150,000 µg FB1/kg body weight, resulting in weight loss and alterations in hematological and biochemical parameters in target organs.

Tuan et al. (2003) demonstrated that feeding FB1 to tropical species at 10, 40, 70 and 150 mg/kg feed for 8 weeks affected growth in Nile tilapia (Oreochromis niloticus) fingerlings. In this experiment, average weight gain in fish fed diets containing 40,000 µg FB1/kg or more were lower. Hematocrit was only reduced in the tilapia given 150,000 µg FB1/kg feed. The ratio of free sphinganine to free sphingosine (Sa:So ratio) in the liver increased at 150,000 µg FB1/kg feed.

Pacific whiteleg shrimp
To the author’s knowledge, the only crustacean species studied to date with respect to sensitivity to FUM is the Pacific whiteleg shrimp (Litopenaeus vannamei). Despite slight variations in testing levels, the few studies available suggest that Litopenaeus vannamei is much more sensitive to FB1 than previously described in freshwater species. García-Morales et al. (2013) have shown that soluble muscle protein concentration was reduced, and changes were observed in the thermodynamic properties of myosin, after 30 days' exposure to FUM in Pacific whiteleg shrimp fed 20 to 200 µg FB1/kg feed.

The same authors reported marked histological changes in the tissues of shrimp fed a diet containing 200 µg FB1/kg feed, and changes in meat quality after 12 days of ice storage in fish fed more than 600 µg FUM/kg feed. The effect of FUM on muscle quality may be of great importance, especially for shrimp-exporting countries, as it directly affects shelf life. The study by Burgos-Hernández et al. in 2005 also confirmed that FB1 causes histological changes in the shrimp hepatopancreas as a result of alterations in trypsin and collagenase activity.

Mexía-Salazar et al. (2008) also observed marked histological changes in the hepatopancreas, as well as necrotic tissue, in shrimp fed 500 µg FB1/kg. These authors also observed changes in both the electrophoretic patterns and the thermodynamic properties of the myosin extracted from shrimp exposed to FB1.


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