Introduction
Plant proteins have been widely used in aquafeeds as a substitute for fish meal diets to support aquaculture development . However, contamination of plant ingredients with toxicogenic fungi is common and occurs in a wide range of these raw materials worldwide . Accidental mycotoxin consumption by fish, can result in various toxic actions and raise concern for both animal health and food safety. In aquaculture, diets contaminated with mycotoxins is a burden on health of cultured fish (Zhonghao et al ., 2023). This study aimed to evaluate the impact of co-exposure to the emerging dietary mycotoxins including Aflatoxin B1 (AFB1), Fumonisin B1 (FB), and Deoxynivalenol (DON) in graded contamination levels , on zootechnical parameters and health indices of gilthead seabream (Sparus aurata).
Materials and Methods
Triplicate aquariums received five experimental diets: A (DON:500, FB:1000, AFB1:5 ppb), B (DON:150, FB:650, AFB1:2 ppb), C (DON:3000, FB:40, AFB1:2 ppb), D (DON:150, FB:40, AFB1:10 ppb), E (DON:150, FB:100, AFB1:2 ppb). The control group (CTRL) was fed with a marine-based , mycotoxin-free diet. The feeding trial lasted 12 weeks. Fish were hand-fed “ad libitum”, two meals per day, 6 days a week. Feed intake and mortalities were daily recorded . Water physiochemical parameters were maintained within the standard levels. Endpoint assessment included evaluation of haematological and immunological parameters, energy utilization (feed-intake and growth) and induced genotoxicity by Single Cell Gel Electrophoresis assay . Liver samples were collected for the determination of hepatic lesions through histological analysis. One-way ANOVA was used to determine the variance among treatments, followed by Tukey’s post hoc test at a significance level of P < 0.05.
Results and Discussion
All treatments containing mycotoxins caused significantly lower food consumption compared to the control group. The group with the highest DON concentration (Group C) showed the lowest feed intake, followed by the group with the highest AFB1 concentration (Group D) . Inferior growth (lower mean weight, length, and total biomass increase) was also recorded in group C, followed by groups D, E and B (Table 1.) , as mentioned before in the case of rainbow trout after dietary exposure to DON (Koletsi et al., 2022). S ignificantly lower haematocrit was recorded in all groups compared to the CTRL , while the lowest value was estimated for the group with the highest FB concentration (group A). Significant decreases in the erythrocytes, leucocytes, and the haematocrit values were previously observed in fish fed with diets with a mixture of FB and AFB1 ( Adeyemo et al.,2022). Diets C and D showed strong effects with significantly elevated Hb and reduced complement, trypsin inhibition and/or alkaline phosphatase activities. The inhibitory action of AFB1 was already shown in Indian major carp with a significant immunosuppressive effect including reduced serum total globulin and reduced bactericidal activities (Sahoo & Mukherjee, 2001 ). Diet A also showed significantly reduced trypsin inhibition . Concerning genotoxicity induced by the mycotoxins, no significant differences on DNA damage were confirmed between examined groups . Liver sections from all mycotoxin groups revealed pathological signs, such as focal to extensive degenerative changes in liver parenchyma and early necrotic changes in some hepatocytes, that showed pyknotic and shrunken nuclei (group C). Mild to extensive hepatocyte cytoplasmic vacuolation, indicating hydropic and fatty degeneration of liver cells was also detected in all mycotoxin groups . In contrast, histopathological examination of liver sections from the CTRL group showed normal hepatic parenchyma and hepatopancreas.
Acknowledgment
The project is co-funded by Greece and the European Union under the Fisheries and Maritime Operational Program 2014-2020 (75% EMFF contribution, 25% National Contribution), Project title: ‘‘Mycotoxins in Aquaculture: Innovative management practices to protect fish and consumer health’’.
References
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