This study aimed to investigate the optimum dietary carbohydrate/lipid (CHO/L) ratio for fingerling blunt snout bream Megalobrama amblycephala (average initial weight: 6.61 AE 0.03 g). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO/L ratios ranging from 1.62 to 24.20. Each diet was tested in four replicates for 10 weeks. Specific growth rate (SGR), feed conversion ratio and nitrogen and energy retention all improved significantly (P < 0.05) as dietary CHO/L ratios decreased from 24.20 to 5.64 but showed little difference (P > 0.05) as dietary CHO/L ratios ranged from 2.45 to 5.64. Hepatosomatic index increased significantly (P < 0.05) as dietary CHO/L ratios increased, whereas intraperitoneal fat ratio showed an opposite trend (P < 0.05). Opposite to moisture content, lipid content of whole body and carcass all increased significantly (P < 0.05) as dietary CHO/L ratios decreased. Liver lipid content showed little difference (P > 0.05) among all the treatments, while liver glycogen content increased significantly (P < 0.05) with increasing CHO/L ratios. High dietary carbohydrate enhanced the activities of liver hexokinase, pyruvate kinase and glucose-6-phosphate dehydrogenase but did not induce hyperglycaemia. Based on the second-order polynomial regression analysis of SGR, the optimal dietary carbohydrate and lipid contents for fingerling blunt snout bream were 291.7 and 81.4 g kg À1 , respectively, with a corresponding dietary CHO/L ratio of 3.58.

A feeding trial was conducted to investigate the effects of dietary fructooligosaccharide (FOS) on growth performance, body composition, intestinal enzymes activities and histology of fingerling Megalobrama amblycephala. A total of 1200 fish (1.42 ± 0.01 g) were fed diets containing graded levels of FOS (0, 0.5, 1, 2, 4 and 8 g kg−1 diet) for 8 weeks in a recirculating system indoor. The weight gain, specific growth rate (SGR) and survival rate were all improved in dietary supplementation of FOS fed fish. Increasing FOS levels resulted in both higher whole‐body lipid and lower moisture contents, whereas ash and protein contents showed no significant differences among all the treatments. Intestinal amylase, protease, Na+, K+‐ATPase, alkaline phosphatase, γ‐glutamyl transpeptidase and creatine kinase activities all increased with dietary FOS levels up to 4 g kg−1 (P < 0.05). Transmission electron microscopy analysis indicated that microvilli length in the mid‐intestine was significantly increased with increased dietary FOS levels (P < 0.05). In conclusion, dietary supplementation of FOS could confer benefits on growth performance, intestinal digestive and absorptive ability, histology of fingerling Megalobrama amblycephala.

We aimed to investigate the effect of xylooligosaccharides (XOS) on the growth performances and lipid metabolism of common carp fed high‐fat diets. 192 fish were randomly distributed into 24 tanks into six groups (four replicates) and were fed with control diet, high‐fat diet (HFD) and HFD supplemented with 5, 10, 20 and 30 g/kgXOS respectively for 8 weeks. Fish fed HFD supplemented with 10 g/kg XOS obtained higher final body weight, weight gain, specific growth rate and protein efficiency ratio compared to those fed control diet and HFD, while feed conversion ratio showed the opposite trend. Fish fed HFD obtained higher hepatosomatic index, abdominal fat, energy intake compared to other groups, whereas the opposite was true for nitrogen retention. High plasma levels of cholesterol, triglycerides, low‐density lipoprotein and low high‐density lipoprotein were observed in fish fed HFD; opposite was true for fish fed HFD supplemented with 10–20 g/kg XOS. The transcription of lipoprotein lipase was up‐regulated, whereas that of carnitine palmitoyltransferase I, peroxisome proliferator‐activated receptors alpha, acyl‐CoA oxidase and CD36 were down‐regulated in fish fed HFD. Opposite trend was observed in fish fed HFD supplemented with 10–20 g/kg XOS as well as the control group. In conclusion, XOS inclusion can benefit the growth performance and lipid metabolism of common carp fed HFD.

An 8-week feeding trial was conducted to evaluate the effects of fish meal (FM) replacement by rice protein concentrate (RPC) with supplementation of microcapsule lysine (ML) or crystalline lysine (CL) on growth performance, muscle development and flesh quality of blunt snout bream. Four isonitrogenous and isoenergetic diets were formulated, including FM diet (containing 50 g/kg FM), RPC diet (FM replaced by RPC), MRPC diet (FM replaced by RPC with ML supplementation) and CRPC diet (FM replaced by RPC with CL supplementation). Fish fed FM diet had significantly higher weight gain, feed efficiency, protein efficiency ratio and nitrogen and energy utilization than that of RPC group, but showed no statistical difference with other treatments. In addition, fish fed RPC diet showed higher muscle fibre frequency in the 20-to 50-μm class but lower >50-μm class and higher cooking loss than that of the other groups. Furthermore, no significant difference was found in whole-body proximate compositions, frequency distribution of <20-μm-diameter fibres, texture, muscle content, collagen, pH 24 hr post-mortem and sensory quality. The results showed that

An 8-week feeding trial was performed to investigate effects of dietary selenium (sodium selenite, Na 2 SeO 3 ; selenium nanoparticle, Nano-Se; selenium yeast, Se-yeast) on the growth, selenium status, antioxidant activities, muscle composition and meat quality of blunt snout bream. Na 2 SeO 3 and Nano-Se were supplemented at 0.2 mg Se kg À1 , and Se-yeast was supplemented at 0.1, 0.2, 0.4 and 0.8 mg Se kg À1 in basal diet; no Se was added as a control. The results indicated that groups of 0.2 and 0.4 mg kg À1 Se-yeast had significantly higher weight gain and Nano-Se, 0.2, 0.4 mg kg À1 Se-yeast had significantly lower feed conversation ratio compared with the control group. The Se concentrations of whole body, muscle and liver linearly increased with increasing dietary Se-yeast levels. Group of 0.4 mg kg À1 Se-yeast significantly increased activities of catalase and glutathione peroxidase. Muscle colour of Nano-Se, 0.2, 0.4 mg kg À1 Se-yeast groups, the waterholding capacity of 0.4, 0.8 mg kg À1 Se-yeast groups showed significant differences compared with the control group. The results suggest that Se-yeast and Nano-Se had a better growth performance than Na 2 SeO 3 at 0.2 mg Se kg À1 , and supplementing appropriate Se-yeast in diet can increase antioxidant activities and enhance meat quality of blunt snout bream.