Effects of different supplementation of dietary tea polyphenols on growth performance, feed utilization and antioxidant capacity of Megalobrama amblycephala

In recent years, the development of antibiotic substitutes with the functions of immune promotion and vegetative growth is the development trend of aquaculture industry. In order to study the effect of dietary tea polyphenols (TP) on the growth performance, feed utilization and antioxidant ability of Megalobrama amblycephala, in the experiment, 240 M. amblycephala with an initial weight of (3.5±1.0) g were selected and randomly divided into 4 groups of 3 replicates, each with 20 fish in each replicate. Four isonitrogen isoenergetic formulation diets supplemented with 0 mg/kg (control group), 100, 300 and 500 mg/kg tea polyphenols were prepared. After the 8-week feeding trial, the growth performance, muscle composition, blood biochemical indicators , liver antioxidant indicators and intestinal antioxidant indicators were measured. The results showed that the WGR of the fish fed 300 mg/kg TP were significantly higher than those of the control group, the PER was significantly higher than those with lower supplementary TP, and the FCR decreased significantly. 500 mg/kg TP supplementation significantly reduced the crude fat content of fish muscle. The TP supplementation significantly reduced plasma GLU content. The content of MDA in the liver and intestines of fish fed 300 mg/kg and 500 mg/kg TP supplementary diets were significantly lower than those in the control group . The content of reduced GSH in the liver and intestine tissues of fish fed 100 mg/kg and 300 mg/kg dietary TP were significantly higher than that in the control group. In addition, the hepatic T-AOC and GSH-Px activity of the 300 mg/kg TP supplementary group were also significantly higher than those in the control group. After the feeding trial, acute liver injury was induced by intraperitoneal injection of 50% concentration of CCl₄ solution. It was found that at 24 hours post-injection, the fish survival rates of the 300 mg/kg and 500 mg/kg TP supplementary groups were significantly higher than those of the 100 mg/kg TP supplementary group, and the survival rates in 100 mg/kg TP supplementary group was significantly higher than the control group. Further analysis on the hepatic antioxidant indexes of fish at 24 hours post-injection, we found that the hepatic MDA content was significantly reduced in the TP supplementary groups. The activity of SOD of the 500 mg/kg TP supplementary group was significantly higher than that in the control group , the content of GSH of the 300 mg/kg TP supplementary group were significantly higher than that in the control group. Considering the physiological effects and practical applications, the dietary supplementation of 300 mg/kg tea polyphenols effectively promoted the growth and feed utilization and improved the antioxidant capacities, and the supplementation at 500 mg/kg impoved anti-injury capacities and protect against oxidative stress damage of M. amblycephala juveniles. The results of this study provide a basis for the study of tea polyphenols in the feeds of pomfrets and provide a reliable reference for their better application in breeding production.