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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]

An 8-week feeding trial was performed to investigate effects of dietary selenium (sodium selenite, Na2SeO3; selenium nanoparticle, Nano-Se; selenium yeast, Se-yeast) on the growth, selenium status, antioxidant activities, muscle composition and meat quality of blunt snout bream. Na2SeO3 and Nano-Se were supplemented at 0.2 mg Se kg−1, and Se-yeast was supplemented at 0.1, 0.2, 0.4 and 0.8 mg Se kg−1 in basal diet; no Se was added as a control. The results indicated that groups of 0.2 and 0.4 mg kg−1 Se-yeast had significantly higher weight gain and Nano-Se, 0.2, 0.4 mg kg−1 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−1 Se-yeast significantly increased activities of catalase and glutathione peroxidase. Muscle colour of Nano-Se, 0.2, 0.4 mg kg−1 Se-yeast groups, the water-holding capacity of 0.4, 0.8 mg kg−1 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 Na2SeO3 at 0.2 mg Se kg−1, and supplementing appropriate Se-yeast in diet can increase antioxidant activities and enhance meat quality of blunt snout bream. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to evaluate the potential of partial replacement of fish meal with rendered animal protein blend ( APB) [meat and bone meal (MBM): expanding blood meal (EBM) = 4 : 1] in the diet of juvenile Chinese soft-shelled turtle Pelodiscus sinensis. Seven isonitrogenous and isoenergetic practical diets replacing 0%, 10%, 20%, 30%, 40%, 50% and 60% fish meal protein by APB were formulated. Weight gain, feed efficiency, protein efficiency and the apparent digestibility coefficients ( ADCs) of dry matter and gross energy in the experimental diets all exhibited no significant difference ( P > 0.05) when dietary fish meal was replaced for 0-40%, but decreased significantly ( P < 0.05) with further increasing substitution levels. However, relative feed intake, ADC of lipid as well as the contents of whole-body moisture, protein, lipid and ash all showed little differences ( P > 0.05) among all the treatments. Nitrogen retention and the ADCs of protein and most amino acids all decreased significantly ( P < 0.05) when fish meal was substituted by more than 30%. The results indicated that fish meal in the practical diet of juvenile Chinese soft-shelled turtle could be replaced by 30-40% using a combination of MBM and EBM without negative effects on growth performance, nutrients digestibility and body composition. [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]