Effects of Zn on growth performance, immune enzyme activities, resistance to disease and intestinal flora for juvenile pearl gentian grouper(Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀) under low fishmeal diet
Wei, Hongjie | Li, Rimei | Yang, Qihui | Tan, Beiping | Ray, Gyan Watson | Dong, Xiaohui | Chi, Shuyan | Liu, Hongyu | Zhang, Shuang
The effects of adding increasing Zn concentrations to fish feed on the growth performance, antioxidant enzyme activity, disease resistance, and intestinal flora abundance and diversity of hybrid grouper larvae (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀) were determined within an 8-week feeding trial period. Zn of graded levels (0 (T0), 20 (T20), 40 (T40), 60 (T60), 80 (T80), 100 (T100) and 150 (T150) mg Zn/kg diet as zinc sulfate) was added to the basal diet and fed to experimental fish with an initial mean weight of 12.00 g.The fish were challenged by Vibrio harveyi for 7 days. Results showed that the survival rate of the dietary Zn groups was obviously higher than that of T0 (P < 0.05). T0 group had the lowest specific growth rate and weight gain rate. The hepatic superoxide dismutase activity of the dietary Zn groups was significantly higher than the T0 group(P < 0.05). T20 group had the lowest hepatic malondialdehyde content. The abundance of Proteobacteria in the midgut decreased significantly (P < 0.05) and the abundance of Bacteroidetes and Firmicutes increased with increasing zinc levels. The optimal dietary Zn inclusion level was 44.52 mg/kg diet, based on the polynomial regression analysis model of WGR for juvenile hybrid grouper.
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