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Six diets were formulated to investigate the success of fish meal (FM) replacement by plant proteins; diet 1 reflected a commercial feed (8% FM), diet 3 contained 4% FM, and diet 5 was devoid of FM. Whereas, diet 2, diet 4, and diet 6 reflected diet 1, diet 3, diet 5, respectively, and supplemented with essential amino acid (EAA). At the end of 8‐week trial, there was no significant difference in survival rate. Significantly higher final weight, weight gain rate, and specific growth rate were recorded in the group fed diet 2 compared with the other treatments (except diet 4) (p < 0.05). Feed conversion ratio of fish fed diet 2 was significantly lower than those fed diets 1, 3, and 5 (p < 0.05). The lowest feed intake and highest protein efficiency rate were found in fish fed diet 2 (p < 0.05). There was no significant difference in whole body compositions between treatments. Plasma aspartate transaminases, alanine aminotransferase, and glucose were significantly affected by dietary treatments (p < 0.05), while plasma protein and albumin contents were not influenced by the treatments. The relative expression of target of rapamycin (TOR) and phosphatidylinositol 3‐kinase, regulatory subunit 1 (alpha) (PIK3R1) in fish fed diet 3 (4% FM) were significantly down‐regulated compared with those fed diet 6 for TOR and diets 4 and 6 for PIK3R1 (p < 0.05). Insulin receptor substrate 1 (IRS‐1) and janus kinase 3 (JAK3) expressions were fluctuated, with the higher levels in fish fed diets 4 and 6. In conclusion, the findings of this study indicate that plant protein mixture supplemented with EAA could be used to substitute FM in practical diet for Megalobrama amblycephala. [ABSTRACT FROM AUTHOR]

Abstract: 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 RPC supplemented with ML or CL could replace fishmeal without any adverse effects on growth performance and flesh quality for blunt snout bream. [ABSTRACT FROM AUTHOR]

Abstract: A feeding trial was conducted to assess the effects of replacing fishmeal (FM) with canola meal (CM) on the growth performance, feed utilization and related gene expression of juvenile blunt snout bream (Megalobrama amblycephala). Fishes were fed with five isonitrogenous (330 g/kg crude protein) and isoenergetic (15 MJ/kg) diets for 16 weeks, which was graded replacing levels of fishmeal (replacing 0, 37.5, 75, 112.5 and 150 g/kg FM with CM). The results revealed that specific growth rate, feed efficiency ratio and protein efficiency ratio of the groups with replacement level up to half were significantly higher than the others, while feed intake was inverse. Peptide transporter 1 (PepT1) mRNA level in the gut was significantly up‐regulated in groups CM25 and CM50 compared to other groups. Relative gene expression of IGF‐1 among groups was extremely significant based on the nonparametric test. Replacement of FM with CM caused a reduction in the hepatic expression of target of rapamycin (TOR), while significant increase trends were observed in hepatic genes of protein kinase B (AKT) and eIF4‐binding protein (4E‐BP2). However, TOR gene expression in the gut was significantly up‐regulated first and then down‐regulated, while mRNA levels of 4E‐BP2 and S6K1 in the gut were first significantly decreased and then increased in CM75, finally significantly decreased to the lowest. The overall results indicated that up to 75 g/kg FM could be replaced by CM (350.5 g/kg CM) in the diets for juvenile blunt snout bream. Besides, these signalling molecules could explain further the mechanisms that juvenile blunt snout can only maintain optimal growth performance up to 75 g/kg FM replacement with CM. [ABSTRACT FROM AUTHOR]

This study aimed to determine the optimal dietary niacin requirement of juvenile Megalobrama amblycephala. Fish, with an average weight of 3.62 ± 0.02 g, were randomly divided into six groups and fed six purified diets with graded levels of niacin (0, 10, 20, 30, 40 and 50 mg/kg) three times daily for 8 weeks. The survival rate, weight gain ( WG), feed conversion ratio, protein efficiency and protein retention all significantly improved ( p < .05) as the dietary niacin level increased from 0 to 30 mg/kg but showed no significant difference ( p > .05) with further increases in niacin levels. The supplementation of 30 mg/kg niacin also led to a significant ( p < .01) reduction in the viscerosomatic index, hepatosomatic index and mesenteric fat index. The dietary niacin levels exhibited minimal effects on whole-body moisture and ash content ( p > .05) but exerted a significant ( p < .05) influence on protein and lipid contents and liver nicotinamide concentrations with high values obtained in fish receiving greater than 30 mg/kg of niacin. In addition, moderate levels of niacin lowered plasma triglycerides, non-esterified fatty acid and low-density lipoprotein cholesterol concentrations ( p < .05). Based on the broken-line regression analysis of WG and liver nicotinamide content, the optimal dietary niacin requirement of juvenile blunt snout bream was 31.25 and 30.62 mg/kg, respectively. [ABSTRACT FROM AUTHOR]

A 16-week feeding trial was conducted to assess the effects of replacing fish meal ( FM) with cottonseed meal ( CM) on the growth performance, feed utilization, plasma biochemical composition and target of rapamycin ( TOR) pathway gene expression of juvenile blunt snout bream ( Megalobrama amblycephala). Five isonitrogenous (36% crude protein) and isoenergetic (16 MJ kg−1) diets with graded replacing levels of CM (replacing 0, 25, 50, 75 and 100% FM with CM) and similar lysine and methionine concentrations were fed to triplicate groups of fish. Results revealed that specific growth rate ( SGR), feed intake and protein efficiency ratio ( PER) of group fed with diets replacing FM with CM up to 50% were significantly higher than others ( P < 0.05). However, final body weight and feed conversion ratio ( FCR) remained similar up to 25% and thereafter significantly decreased and increased, respectively, as the replacement level increased ( P < 0.05). Replacement levels significantly decreased hepatosomatic index and viscerosomatic index ( P < 0.05), but did not significantly affect condition factor and whole body compositions. Free gossypol mainly accumulated in liver and significantly increased in diets CM75 and CM100 than CM0 ( P < 0.05). Replacement significantly influenced plasma urea contents ( P < 0.05). Meanwhile, increasing replacement of FM with CM in diets increased insulin-like growth factor I ( IGF-1) gene expression in liver of blunt snout bream. Target of rapamycin ( TOR) gene expression in diet CM100 was significantly lower than that in diets CM0 and CM75, while the eukaryotic translation initiation factor 4E-binding protein 2 (4E- BP2) gene expression was not affected by the replacement level of CM in diets. Therefore, based on final body weight and FCR, it suggested that up to 25% of FM (150 g kg−1 in basal diet) could be replaced by CM in diets, which was 112.5 g kg−1 FM and 192.9 g kg−1 CM, for juvenile blunt snout bream. [ABSTRACT FROM AUTHOR]

A 9-week feeding trial was conducted to estimate the dietary isoleucine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded isoleucine levels ranging from 5.3 to 20.1 g kg−1 dry diet. At the end of the experiment, weight gain ( WG), specific growth rate ( SGR), feed efficiency ratio ( FER) and protein efficiency ratio ( PER) increased with increasing dietary isoleucine level up to 11.1 g kg−1 dry diet, and dietary isoleucine level above 14.2 g kg−1 dry diet declined these performances. Dietary isoleucine levels (14.2 and 17.3 g kg−1 dry diet) significantly improved whole-body protein content, but decreased whole-body lipid, plasma triglyceride and cholesterol contents. Significantly lower visceral fat index ( VFI) in fish fed with 14.2 g kg−1 dietary isoleucine was observed compared to those fed with deficient or excessive isoleucine. Dietary isoleucine supplementation significantly increased plasma isoleucine concentration, while plasma valine and leucine concentrations showed a reversed trend. Dietary isoleucine levels regulated the target of rapamycin ( TOR) gene expression and improved plasma superoxide dismutase ( SOD) activity in juvenile blunt snout bream. Based on second-order polynomial regression model analysis of SGR and FER, the optimum dietary isoleucine requirement was estimated to be 13.8 g kg−1 dry diet (40.6 g kg−1 dietary protein) and 14.0 g kg−1 dry diet (41.2 g kg−1 dietary protein), respectively. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of dietary choline supplementation on growth, lipid deposition and intestinal enzyme activities of Megalobrama amblycephala. Fish were fed four diets with two lipid levels (50 and 150 g kg−1) and two choline supplementations (600 and 1600 mg kg−1) for 8 weeks. Feed conversion ratio ( FCR), viscerosomatic index ( VSI), hepatosomatic index ( HSI), intraperitoneal fat ( IPF) ratio, whole-body and muscle lipid contents, intestinal lipase activities and lipoprotein lipase ( LPL) activities all increased significantly ( P < 0.05) as lipid levels increased, whereas the opposite was true for whole-body and muscle moisture contents and intestinal amylase activities. VSI, IPF ratio and whole-body lipid contents all decreased significantly ( P < 0.05) with increasing dietary choline supplementations. Weight gain, muscle moisture content all increased significantly ( P < 0.05) with increasing dietary choline supplementations when dietary lipid levels reached 150 g kg−1, whereas the opposite was true for FCR, IPF ratio, IPF and liver LPL activities. In addition, abnormal hepatocytes were found in the liver of fish fed 150 g kg−1 lipid with 600 mg kg−1 choline supplementation. The result of this study indicated that extra choline supplementation can improve growth performance, intestinal enzymes activities and reduce excessive lipid deposition of M. amblycephala fed high lipid. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the optimal dietary biotin requirement of juvenile Megalobrama amblycephala. Quadruple groups of fish (initial average weight 2.01 ± 0.01 g) were fed thrice daily with six isonitrogenous and isoenergetic purified diets containing 0 (basal diet), 0.015, 0.049, 0.158, 0.624 and 2.49 mg kg−1 biotin, respectively, for 8 weeks. Results showed that survival rate, final weight, feed intake, specific growth rate, protein efficiency ratio and nitrogen retention efficiency all increased significantly ( P < 0.01) as dietary biotin levels increased from 0 to 0.049 mg kg−1, whereas the opposite was true for feed conversion ratio. Dressout percentage, condition factor, hepatosomatic index, viscera/body ratio all showed no significant difference ( P > 0.05) within the biotin range tested. Contrary to moisture content, whole-body protein and lipid contents showed a positive correlation with dietary biotin levels. In addition, liver biotin content increased significantly ( P < 0.05) with increasing dietary biotin levels up to 0.624 mg kg−1. Hepatic pyruvate carboxylase ( PC) and acetyl- Co A carboxylase ( ACC) activities both showed an increasing trend as dietary biotin levels increased. Based on the regression analysis of weight gain, hepatic PC and ACC activities, the optimal dietary biotin requirement of juvenile Megalobrama amblycephala is estimated to be 0.063, 0.071 and 0.075 mg kg−1, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 ± 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−1, respectively, with a corresponding dietary CHO/L ratio of 3.58. [ABSTRACT FROM AUTHOR]

A 12-week feeding trial was conducted to determine dietary choline requirement for juvenile Megalobrama amblycephala. The basal diet was formulated to contain 310 g kg−1 diet from vitamin-free casein and gelatine. Choline chloride was supplemented to the basal diet to formulate six purified diets containing 0, 250, 500, 1000, 2000 and 4000 mg kg−1, respectively. Each diet was randomly fed to quadrupled groups of Megalobrama amblycephala with initial average weight 1.84 ± 0.04 g in a flow-through system. Results showed weight gain was increased significantly with increasing dietary choline levels ( P < 0.01). Lipid content of liver decreased significantly as dietary choline concentration increased ( P < 0.01), whereas lipid content of dressed carcass showed opposite trend ( P < 0.01), and lipid content of whole-body was unaffected by dietary choline supplementation. Broken- line regression of weight gain, liver and muscle choline concentration showed choline requirements of Megalobrama amblycephala of 1198, 1525 and 1365 mg kg−1, respectively. In addition, dietary choline supplementation significantly improved lipid content of dressed carcass but not the content of whole body of blunt snout bream. [ABSTRACT FROM AUTHOR]