Dietary garlic and chitosan alleviated zearalenone toxic effects on performance, immunity, and challenge of European sea bass, Dicentrarchus labrax, to Vibrio alginolyticus infection

摘要

The current investigation was carried out to assess the efficacy of dietary garlic (GP) and/or chitosan (CH) powders to protect European sea bass, Dicentrarchus labrax, against the adverse effects of zearalenone (ZEN) toxicity. Hence, ZEN (0.725 g/kg diet) was incorporated in a fish diet alone or with 30 g GP and/or 10 g CH/kg diet and the treatments were assigned as a control diet (T1), a control diet + ZEN (T2), a control diet + ZEN + GP (T3), a control diet + ZEN + CH (T4), and a control diet + ZEN + GP + CH (T5). Fish (30.7 +/- 0.6 g) fed one of the tested diets up to apparent satiation thrice a day for 4 weeks. After the feeding trial, fish were intraperitoneally injected with pathogenic bacteria Vibrio alginolyticus for 14 days during which fish mortality was observed. The dietary ZEN inhibited fish growth and feed utilization; meanwhile, co-supplementation of GP and/or CH restored the reduced fish performance as a result of reducing the ZEN toxicity. The ZEN toxicity induced macrocytic hypochromic anemia in European sea bass; however, significant reductions were observed in values of red blood cells (RBCs), hemoglobin (Hb), hematocrit (Ht), and mean corpuscular hemoglobin concentration (MCHC) together with significant elevations in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) values in comparison with the control fish. Likewise, lymphopenia, monocytosis, leucopenia, eosinophilia, neutrophilia, and thrombocytopenia were the characteristic features of ZEN-toxicated fish with drastic reduction in white blood cells (WBCs) counts. Significant reductions in total protein, albumin, globulin, and lysozyme were also observed in fish serum due to ZEN toxicity. The co-supplementation of GP and/or CH to ZEN-fed fish elevated significantly values of RBCs, Hb, MCHC, and WBCs count with decreasing and increasing of its constituents. Significant rises in total protein, albumin, globulin, and lysozyme were observed with co-supplementation of GP and/or CH to ZEN-toxicated fish to be near these fed on the control diet. The ZEN toxicity also suppressed the fish immunity and subsequently elevated fish susceptibility to V. alginolyticus infection causing highest fish mortality as compared with other treatments. The co-supplementation of GP or CH to fish significantly enhanced their immunity causing a high relative percent of survival (RSP) of fish after bacterial infection (18.8 or 43.8%, respectively); meanwhile, fish fed both of GP and CH showed better RSP (68.8%). On the other hand, the co-supplementation of GP or CH reduced the ZEN residue (1.18 and 0.87 mu g/kg dry weight) in fish muscles. These results show that CH was more effective than GP in enhancing fish immunity and protection against ZEN toxicity, whereas the co-supplementation of both GP and CH was most effective in protecting fish against ZEN toxicity resulting in lowest ZEN residue (0.53 mu g/kg dry weight) in fish muscles.