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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 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 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]