Effects of dietary tea polyphenols on growth, immunity and lipid metabolism of juvenile black carp Mylopharyngodon piceus

An 8-week feeding experiment was aimed to investigate the effect of dietary tea polyphenols (TP) on growth, immunity and lipid metabolism in juvenile black carp Mylopharyngodon piceus (initial weight 5.90 +/- 0.03 g). Tea polyphenols were added at different levels (0, 25, 50, 100 and 500 mg/kg; TP0, TP25, TP50, TP100 and TP500). The results are as follows: the highest specific growth rate (SGR) and condition factor (CF) and activity of trypsin (TRS) of intestine in TP50, but SGR and activities of lipase (LPS)and TRS of intestine and content of whole body crude protein in TP500 were remarkably lower than TP0. Compared with TP0, content of serum superoxide dismutase (SOD) and glutamic oxalacetic transaminase (GOT) remarkably increased (p < .05), but contents of glutathione (GSH), glutathione peroxidase (GSH-Pox), malondialdehyde (MDA), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) were significantly decreased (p < .05), content of cortisol was remarkably lower in TP50 and TP100 (p < .05), expression of growth hormone (GH) and melanocortin 4 receptor (MC4R) in liver and GH in muscle were remarkably up-regulated in TP50, but expression of apolipoprotein A-1 (ApoA1), GH and MC4R of intestine, ApoA1 of liver and MC4R of muscle in TP500 were remarkably down-regulated, contents of complement 3 (C3), complement 4 (C4), high-density lipoprotein cholesterol (HDL-C) and LDL-C were significantly reduced in TP500 (p < .05). In conclusion, TP could improve growth performance and oxidative capacity on juvenile black carp, and its optimal dosage was 50 mg/kg.