Effects of tea polyphenols on the growth performance, carbohydrate metabolism of grass carp (Ctenopharyngodon idellus).

To investigate the effects of tea polyphenols (TPs) on the growth and carbohydrate metabolism of grass carp (Ctenopharyngodon idella), 0 (control group), 250, 500, 1000, 2000, and 4000 mg kg−1 TPs were added to the basal diet and fed to grass carps for 8 weeks. The results show that 500 mg kg−1 group exhibited the significantly highest feed conversion efficiency (FCE) and specific growth rate (SGR) (p <.05) and significantly higher activities of pyruvate kinase (PK), lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) (p <.05). The livers of the control group and 500 mg kg−1 group were subjected to RNA‐Seq, and the expressions of glycogen phosphorylase (PYG) and sucrase‐isomaltase (SI) genes were upregulated, while that of glucose‐6‐phosphatase (G6PC) was downregulated, and these promoted glycogen catabolism. The expressions of glucokinase (GK), PK, 6‐phosphofructokinase (PFK), glucose‐6‐phosphate 1‐dehydrogenase (G6PD) and fructose‐bisphosphate aldolase A (ALDOA) genes were upregulated to promote glucose catabolism. The results indicate that 500 mg kg−1 TPs could upregulate the expressions of some genes that promote carbohydrate decomposition, increase the activities of carbohydrate decomposition enzymes and enhance the utilization of carbohydrates, thereby improving the FCE and SGR. [ABSTRACT FROM AUTHOR]