Individual and combined effects of dietary chlorogenic acid and quercetin supplementation on the growth, lipid metabolism and flesh quality of grass carp, Ctenopharyngodon idellus

The purpose of this study was to evaluate the individual and combined effects of dietary chlorogenic acid and quercetin supplementation on the growth, lipid metabolism and flesh quality of Ctenopharyngodon idellus (C. idellus). Fish (59.7 ± 0.3 g) were fed for 60 days with five diets, including a basal diet not added (CON) or added with chlorogenic acid (CGA, 400 mg/kg), quercetin (QC, 400 mg/kg), and their combinations (CGA:QC=1:1) with 400 mg/kg and 800 mg/kg (CGA:QC-400; CGA:QC-800). The weight gain was increased (+4.00 %, +4.41 %), and the feed conversion ratio was decreased (-0.07, -0.08) by individual supplementation with CGA and QC (P<0.05), but not by their combinations (P>0.05). In addition, dietary CGA and QC promoted the apparent digestibility of dry matter and protein and the activities of intestinal amylase and protease (P<0.05). The CGA, QC and CGA:QC-800 groups presented higher activities of flesh superoxide dismutase, flesh glutathione peroxidase (GSH-Px) and serum GSH-Px, as well as lower contents of protein carbonyl and malondialdehyde (MDA) in flesh and MDA in serum than those of CON group (P<0.05). An increase in flesh hardness, water-holding capacity, and total collagen, heat-insoluble collagen and n-3 polyunsaturated fatty acids contents was observed in the CGA, QC and CGA:QC-800 groups (P<0.05). The four supplements reduced mesenteric lipid-somatic index, flesh n-3/n-6 ratio and serum triglycerides (P<0.05), and the CGA:QC-400 and CGA:QC-800 groups also showed lower lipid content in flesh than CON group (P<0.05). Taken together, the individual supplementation of dietary CGA and QC enhanced the growth performance, lipid metabolism and flesh quality of C. idellus, and their combination presented synergistic effect only on lipid metabolism.