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This study investigated the effects of four flavonoids on growth and flesh quality of grass carp (Ctenopharyngodon idellus). Five diets were designed with the supplementation of quercetin (QC), rutin (RT), baicalein (BC) and catechin (CC) in basal diet (control) and were fed to grass carp (59.7 ± 0.2 g) for 60 days. The fish fed QC and RT diets, rather than BC and CC diets, showed higher weight gain (+4.0%, +3.9%) and lower feed conversion ratio (−0.07, −0.06) than the control fish. The contents of total collagen, heat‐soluble collagen, total free amino acids and flavour amino acids in flesh were significantly increased by the supplementation of QC and RT in diets. The SOD activity and the contents of C22:5, C22:6 and n‐3 PUFA were significantly increased, and the malondialdehyde and protein carbonyl contents were significantly decreased in the QC, RT and CC groups. In the metabolomics profiling of muscle, 102 and 68 named differential metabolites were identified in the QC and RT groups, and these metabolites were found to be involved in the pathways of "lipid metabolism" and "amino acid metabolism." In addition, the mRNA expressions of IGF‐1, PI3K, AKT and FAS in flesh were significantly up‐regulated in QC and RT groups. In summary, dietary QC and RT promoted the growth and flesh quality of grass carp which might be associated with IGF‐1/TOR, Nrf2, TGF‐β/Smad4 and PPAR signalling pathway. [ABSTRACT FROM AUTHOR]

To investigate the effects of dietary tributyrin (TB) on grass carp (Ctenopharyngodon idella), five diets were prepared with supplementing TB at 0 (TB‐0), 200 (TB‐200), 400 (TB‐400), 600 (TB‐600) and 800 (TB‐800) mg/kg and then fed to grass carp with initial body weight of 17.0 ± 0.2 g for 60 days. TB‐400 and TB‐600 groups presented higher weight gain, higher retention of protein, lipid, ash and lower feed conversion ratio than TB‐0 group (p <.05), and TB‐400 group also showed higher digestibility of dry matter and protein as well as intestinal amylase activity than TB‐0 group (p <.05). Compared with the control, the serum superoxide dismutase activity was increased, and malondialdehyde content was decreased in TB‐400 and TB‐600 groups (p <.05), while TB‐200 and TB‐400 groups presented higher serum lysozyme activity than TB‐0 group (p <.05). The villus height in foregut was increased in all the tributyrin‐supplemented groups, but the villus height in midgut was increased only in TB‐400 and T‐600 groups (p <.05). The relative abundance of Erysipelatoclostridium tended to increase, and Aeromonas tended to decrease in TB‐400 group. In conclusion, dietary tributyrin promoted the growth and feed utilization, enhanced serum antioxidant capacity and improved intestinal health of grass carp. Based on growth performance, the appropriate dietary supplementation of tributyrin is 443.5 mg/kg by using quadratic regression analysis. [ABSTRACT FROM AUTHOR]

It was previously shown that the influence of high‐energy diets on growth and flesh quality of grass carp was closely related to energy resource. The mechanisms were explored in this study by investigating the hepatic lipid and glucose metabolism of grass carp. Juvenile grass carp (Ctenopharyngodon idella) with initial body weight (55.0 ± 2.5) g were fed with four purified diets for 11 weeks, with four replicates per diet and 20 fish per replicate. Three high‐energy diets with high level of carbohydrate, fat and protein were prepared, and their gross energy was 11% higher than that of control diet. Results showed that the highest contents of hepatic crude fat, total saturated fatty acids, n‐6 unsaturated fatty acids and glycogen, as well as the highest grade of hepatocyte steatosis were observed in grass carp fed the high‐carbohydrate diet. Data on hepatic mRNA expression indicated that the high‐carbohydrate diet increased the genes expression including pk, gck, g6pd, fas and acc‐1, while the high‐fat diet significantly increased the genes expression including pk, gck, fbp, pck, lpl and hsl. The high‐fat and high‐carbohydrate diets activated hepatic AMPK/ACC pathway, whereas inhibited TOR/SREBP‐1 pathway. In conclusion, the high‐carbohydrate diet had a stronger effect on the hepatic lipid accumulation than the high‐fat diet in grass carp. The acceleration of lipolysis, glycolysis and gluconeogenesis in liver improved the utilization of the high‐fat diet in grass carp. Besides, the high‐carbohydrate diet can promote hepatic glycolysis and pentose phosphate shunt and inhibit gluconeogenesis in grass carp. [ABSTRACT FROM AUTHOR]

Both cottonseed meal (CSM) and dried distiller's grains with solubles (DDGS) are important plant protein sources for fish. This study investigated the effects of dietary DDGS inclusion to replace different portions of CSM on growth performance, muscle texture, health status as well as myogenic‐related genes expression of juvenile grass carp (initial weight: 5 g). A 60‐d feeding trial was performed by feeding fish with three isonitrogenous and isoenergetic diets containing different levels of DDGS (0, 10.3% and 20.6%). The highest growth and feed efficiency occurred at 20.6% DDGS dietary inclusion. Body condition factor, hepatosomatic index, serum ALT and AST as well as hepatic GSH and T‐SOD all showed a downward trend with increasing dietary inclusion of DDGS (p <.05). Collagen content in raw muscle increased with DDGS inclusion. However, DDGS inclusion decreased muscle texture indices and muscle fibre density, while increased muscle fibre diameter (p <.05). Dietary DDGS inclusions significantly upregulated the expression of fgf6a, myh1, myh2 and myh4 in muscle, while downregulated the expression of myod, myf5, myog, mrf4, mstn1, fgf6b and myh7. Overall, dietary DDGS replacing CSM positively affects growth by regulating gene expression involved in myogenesis and hypertrophy, while depressed antioxidant capacity. [ABSTRACT FROM AUTHOR]

Rutin is a natural flavone derivative with many biological activities. To investigate the effects of dietary rutin on growth, serum antioxidant response and flesh quality of grass carp (Ctenopharyngodon idella), six diets were prepared with the rutin inclusion at 0 (control diet), 0.2, 0.4, 0.6, 0.8 and 1.0 g/kg, respectively. Grass carp with initial body weight of 18.5 ± 0.2 g were fed with the six diets for 60 days. The weight gain was increased from 348.5% (the control) to 364.4%, 366.5% (p <.05), and feed conversion ratio was decreased from 1.56 (the control) to 1.49, 1.48 (p <.05), respectively, by the supplementation of 0.8 and 1.0 g/kg rutin in diets. Serum SOD activity was increased by the addition of 0.2–1.0 g/kg rutin (p <.05), and serum MDA content was decreased by the addition of 0.4–1.0 g/kg rutin (p <.05). The inclusion of 1.0 g/kg rutin and 0.6–1.0 g/kg rutin significantly increased the collagen content and the total free amino acids in flesh (p <.05), respectively. The content of n‐3 PUFA in flesh was also promoted by the inclusion of 0.2 and 0.6 g/kg rutin (p <.05). However, dietary rutin did not significantly affect the flesh texture and water‐holding capacity. In conclusion, dietary rutin could improve the growth, antioxidant response ability and flesh quality of grass carp, and the recommended supplemental level of rutin was 0.8–1.0 g/kg. [ABSTRACT FROM AUTHOR]

The present research evaluated the effects of graded levels of dietary fibre on growth, digestive and absorptive capacities, and the potential underlying mechanisms in on‐growing grass carp (Ctenopharyngodon idella). Grass carp (123.00 ± 0.70 g) were fed diets with graded levels of neutral detergent fibre (NDF: 97.8, 119.0, 140.2, 159.4, 181.2 and 201.6 g/kg diet) for 60 days. Besides, a 2‐week digestion experiment was conducted to explore the effect of dietary fibre on the apparent digestibility coefficients (ADC) of feed. The results showed that optimum dietary fibre level (140.2 or 159.4 g/kg diet) increased feed intake, per cent weight gain, specific growth rate and the ADC of dietary protein (p <.05); increased the activities of digestive and brush border enzyme; and up‐regulated intestinal amino acid transporter mRNA levels (SLC1A5 and SLC6A19b, p <.05) partially associated with activation of TOR signalling pathway. However, high dietary fibre levels (NDF levels ≥181.2 g/kg diet) were not conducive to the digestion and absorption of nutrients, resulting in the decline of growth performance. Thus, based on the quadratic regression analysis for per cent weight gain and feed efficiency, the optimum (143.9 and 134.5 g/kg diet) and maximum tolerance (189.8 and 171.2 g/kg diet) levels of dietary NDF were estimated for on‐growing grass carp. [ABSTRACT FROM AUTHOR]

The present research was designed to investigate the growth promoting and immunostimulating properties of Moringa oleferia leaf meal (MLM) in grass carp. Juvenile grass carp (22.03 g ± 1.164) were fed with diets supplemented with 0, 50, 100 and 150 g/kg MLM for 48 days. At the end of feeding trial, skin mucus was used for analysis of lysozyme, protease, antiprotease and peroxidase activity. Head kidney was used for expression analysis of tumour necrosis factor‐alpha, interleukin‐8 and interferon‐γ. The obtained results showed that fish fed with 100 and 150 g/kg MLM had significant increase in weight gain and specific growth rate (p <.05). However, condition factor was not altered. The MLM (50 and 100 g/kg) inclusion resulted in higher mucus lysozyme and protease activity (p <.05), while peroxidase activity increased only in fish fed with 100 g/kg MLM and antiprotease activity was not altered. Expression of tnf‐α increased in a dose‐dependent manner, and significant (p <.05) increase was recorded in fish fed with 150 g/kg MLM. The expression of il‐8 and ifn‐γ increased in fish fed with 50 and 150 g/kg MLM; however, the increase was not significant (p >.05). In conclusion, supplementing juvenile grass carp feed with MLM up to 150 g/kg has growth promoting and immunostimulating effects. [ABSTRACT FROM AUTHOR]

To evaluate the effects of dietary nano‐selenium (Nano‐Se) on antioxidant capacity and hypoxia tolerance of grass carp fed with high‐fat diet, experimental fishes were fed Nano‐Se supplemented diets at doses of 0 (Control), 0.3, 0.6, 0.9 and 1.2 mg/kg for 10 weeks. After feeding trial, a part of the fishes were exposed to hypoxia stress. Results showed that the survival ratio of grass carp significantly increased in 0.6 and 0.9 mg/kg Nano‐Se group, and the content of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) significantly decreased in 0.6–1.2 mg/kg Nano‐Se groups compared with the control group. In addition, dietary Nano‐Se significantly enhanced glutathione peroxidase (GPX) activity and reduced the malondialdehyde (MDA) content in fishes fed diets with 0.3 and 0.6 mg/kg Nano‐Se. Dietary Nano‐Se significantly elevated mRNA expression of GPX1 and catalase (CAT) by promoting the mRNA expression of NF‐E2‐related nuclear factor 2 (Nrf2) in the hepatopancreas. After hypoxia stress, the GPX and superoxide dismutase (SOD) activities were significantly enhanced, and the MDA content and mortality rate consequently decreased in fishes fed diets with 0.3 and 0.6 mg/kg Nano‐Se. In summary, these results suggested that optimal Nano‐Se in diet enhanced the antioxidant capacity and hypoxia tolerance of grass carp. [ABSTRACT FROM AUTHOR]

An 8‐week growth trial was conducted to investigate the effects of dietary Arg levels (7.6, 12.3, 17.9, 22.4 and 28.6 g/kg diet) on growth performance, hepatopancreatic antioxidant capacity, intestinal morphology and growth‐related gene expressions of juvenile grass carp (Ctenopharyngodon idellus). The results showed that SGR in Arg22 and Arg28 groups was lower than in Arg12 and Arg17 groups (p < 0.05). Serum NO content in Arg7 group was lower than other groups. Hepatopancreatic GSH‐Px activity was higher in Arg17 group than in Arg7 group, while MDA content showed the opposite trend. Hepatopancreatic IGF‐1 expression tended to increase with Arg from 7.6 to 22.4 g/kg and then decreased in Arg28 group (p < 0.05), while IGFBP‐1 expression increased with Arg level. Muscle mRNA expressions of TOR and S6K1 showed quadratic trends as dietary Arg level increased, which were higher in Arg17 group than in Arg22 and Arg28 groups (p < 0.05). Higher mRNA expression levels of y+LAT1, y+LAT2 and PepT1, as well as higher villus height and villus width in foregut, were all observed in Arg17 group. The optimal dietary Arg level based on SGR by the quadratic model was 15.3 g/kg diet for juvenile grass carp, corresponding to 54.7 g/kg dietary protein. [ABSTRACT FROM AUTHOR]

This study was conducted to compare the growth-promoting and flesh quality -improving effects of three active compounds in Eucommia ulmoides (EU) on grass carp (Ctenopharyngodon idella). Four iso-nitrogenous diets supplemented with 400 mg/kg inclusion of geniposidic acid (GA), chlorogenic acid (CGA), geniposide (GP) and their combination (GA:CGA:GP = 1:1:1, the mixture) were prepared and fed to grass carp (47.1 ± 0.6 g) for 75 days. The results indicated that weight gain was increased by 5.22%, and feed conversion ratio decreased by 0.07 by dietary CGA (p < 0.05). In flesh quality, the four supplementations significantly increased muscle fibre density, total collagen and alkaline-insoluble collagen in skin, and reduced steaming loss of flesh. In addition, dietary CGA, GP and the active compounds mixture further increased total collagen, alkaline-insoluble collagen and amino acid in flesh. In collagen genes expression, the expression of COL1A1 in muscle and skin was significantly promoted by the supplementation of GA, CGA, GP and their combination (p < 0.05). In conclusion, the supplementation of GA, CGA, GP and their combination improved the flesh quality of grass carp, and the growth was increased by CGA. CGA played more important roles in growth-promoting and flesh quality-improving effects than GP and GA. [ABSTRACT FROM AUTHOR]

Glutamine (Gln) is a conditionally essential free amino acid that has been widely used in aquaculture. The present study showed that appropriate levels of dietary Gln could significantly improve growth performance and increase lipase and trypsin activity, mucosal thickness (MT) and the number of lymphocytes. The levels of glycine (Gly) in the 6 g/kg Gln group, threonine (Thr) in the 12 g/kg group and lysine (Lys) in the 6 and 9 g/kg group were increased significantly, while glutamate (Glu) and serine (Ser) concentrations decreased significantly with increasing dietary Gln levels from 3 to 12 g/kg. Moreover, the 12 g/kg dietary Gln level could improve the concentration of malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH‐PX) and the total antioxidant capacity (T‐AOC). In addition, 3 g/kg Gln upregulated the gene expression of aminopeptidase N (APN), caudal‐related homeobox gene (CDX2), L‐type amino acid transporter 2 (LAT2), oligopeptide transporter 1 (PEPT1), specificity proteins 1 (SP1) and 3 (SP3), and peroxisome proliferator‐activated receptor α (PPAR‐α) but downregulated PPAR‐γ gene expression compared to that in the control group. Taken together, these findings suggest that Gln could improve the growth performance, antioxidant status and intestinal function of grass carp. [ABSTRACT FROM AUTHOR]

Abstract: This study was conducted to investigate the effects of dietary geniposidic acid (GA) on growth performance, flesh quality and collagen gene expression of grass carp (Ctenopharyngodon idella). The fish with an initial body weight of 47.1 ± 0.8 g were fed one of the seven diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g/kg) and GA‐supplemented diets (200, 400, 600, 800 and 1,000 mg/kg GA) for 75 days. The growth performance and muscle proximate composition showed no difference among groups (p > .05). Dietary GA (200–1,000 mg/kg) increased the contents of total collagen and alkaline‐insoluble collagen in skin (p < .05), and high supplementation of GA (600–1,000 mg/kg GA) and EU increased the contents of total collagen, alkaline‐insoluble collagen and total amino acids (p < .05), but reduced the lipid level in muscle (p < .05). In collagen gene expression, EU and 200–1,000 mg/kg GA increased COL1A1 expression in muscle and skin (p < .05), but the expression of COL1A2 was increased only by high supplementation of GA (1,000 mg/kg, or 800–1,000 mg/kg) (p < .05). In conclusion, dietary GA improved the flesh quality of grass carp, and the supplementation level was estimated to be 600 mg/kg diet. [ABSTRACT FROM AUTHOR]

The study was to investigate effects of dietary chlorogenic acid (CGA) on growth performance, flesh quality and serum biochemical indices of grass carp (95.1 ± 0.3 g) ( Ctenopharyngodon idella) fed seven different diets, including control diet, Eucommia ulmoides (EU)-supplemented diet (20 g kg-1) and CGA-supplemented diets containing 100, 200, 400, 600 and 800 mg/kg CGA. Contents of collagen and alkaline-insoluble collagen in muscle and skin were significantly increased by dietary CGA and EU ( p < .05). Total essential amino acids (TEAA) and total amino acids (TAA) in muscle of grass carp fed EU diet or 400, 600 and 800 mg/kg CGA diet were significantly higher than those of fish fed control diet and 100 and 200 mg/kg CGA diet ( p < .05). Fish fed 200-800 mg/kg CGA showed significantly lower muscle crude lipid content than EU, control and 100 mg/kg CGA groups ( p < .05). Fish fed CGA-supplemented diets (100-800 mg/kg) had significantly higher muscle fibre density and lower muscle fibre diameter than control group ( p < .05). In conclusion, supplementation of CGA improved flesh quality of grass carp, and supplemental level of CGA for improving flesh quality and growth was estimated to be 400 mg/kg diet. [ABSTRACT FROM AUTHOR]

In this study, Bacillus natto NT was evaluated for use as a probiotic supplement in the feeds on the growth performance and the growth-related genes' and micro RNAs' (mi RNAs) expression in the skeletal muscle of grass carp ( Ctenopharyngodon idella). Grass carps (ave. wt. 43.96 ± 0.27 g) were fed diets supplemented with 1.87 × 109 (Bn1), 3.73 × 109 (Bn2), 5.60 × 109 (Bn3), 7.47 × 109 (Bn4) and 9.33 × 109 (Bn5) B. natto NT cells per 100 g feed for 56 days. The control group (BnC) was not supplemented with the B. natto NT. The fish of Bn3, Bn4 and Bn5 groups displayed better growth performance and lower feed conversion ratio ( FCR) than the other groups ( P < 0.05). Compared with the fish of BnC group, miR-1a, miR-181a, miR-23a and miR-206 expressions increased ( P < 0.05), and the myostatin and myocyte enhancer factor C ( MEF2C) mRNAs were down-regulated ( P < 0.05) in the fish of Bn4 and Bn5 groups. The specific growth rate analysis and apparent expressional regulation of the growth-related mi RNAs and genes stimulated by B. natto suggest the potential application of B. natto in improving the growth performance on the grass carps. [ABSTRACT FROM AUTHOR]

A 76-day feeding trial was carried out to evaluate the effects of Lysine and Methionine supplementation on growth and digestive capacity of grass carp ( Ctenopharyngodon idella) fed plant protein diets using high-level canola meal ( CM). Fish with initial average weight 103.9 ± 0.6 g were fed three extruded diets. Fish meal ( FM) diet was formulated as the normal control with 40 g kg−1 FM and 300 g kg−1 CM; CM diet was prepared by replacing all FM with CM (total 340 g kg−1) without Lys or Met supplementation; CM supplement ( CMS) diet was similar to CM diet but was supplemented with essential amino acids ( EAA) to ensure the levels of Lys and Met similar to those in the FM diet. Feed intake, feed efficiency and specific growth rate of the grass carp fed CMS and FM diets were similar ( P > 0.05), but higher than those of the grass carp fed CM diet ( P < 0.05). The hepatosomatic index, relative gut length, intestosomatic index and intestinal folds height were significantly improved in fish fed FM and CMS diets as compared to CM diet ( P < 0.05). Lower activities of trypsin, lipase and amylase in hepatopancreas were observed in fish fed CM diet ( P < 0.05). Three hundred and forty gram per kilogram CM without Lys or Met supplementation significantly decreased trypsin, lipase and amylase m RNA levels in hepatopancreas ( P < 0.05). These results indicated that the high supply of CM (340 g kg−1) in plant protein (200 g kg−1 soybean meal and 100 g kg−1 cottonseed meal) diets decreased digestive ability through decreasing digestive enzyme activities and enzyme gene's expressions of grass carp, and these side effects can be reversed by supplementing Lys and Met. Therefore, CM could be high level used in a plant protein blend-based extruded diet for grass carp as long as EAA were supplemented. [ABSTRACT FROM AUTHOR]

A growth trial lasting for 12 weeks was conducted in 21 net cages to determine the dietary potassium ( K) requirement of subadult grass carp ( Ctenopharyngodon idellus) (Average weight: 331.3 g). Seven isonitrogenous and isoenergetic semi-purified diets were compounded with different dietary K level. The specific growth rate ( SGR) of fish was significantly ( P < 0.05) improved by dietary K supplementation, SGR and the gill Na+-K+ ATPase activity increased first and then decreased ( P < 0.05) as dietary K level increased. The highest SGR and gill Na+-K+ ATPase activity values were both observed at 6.38 g kg−1 group. Dietary K level showed significant ( P < 0.05) effect on serum superoxide dismutase ( SOD) and glucose ( GLU), the maximum values of SOD and GLU were in 8.42 and 6.38 g kg−1 group, respectively. The body lipid content of the 6.38 g kg−1 group was significantly ( P < 0.05) lower than that of the control. However, the ash content in the 8.42 g kg−1 group was significantly higher than those in the 1.21, 2.21, 4.41 and 6.38 g kg−1 group. When dietary protein was 320 g kg−1 and the waterborne potassium ranged from 6.86 to 9.10 mg L−1, the dietary K requirement for subadult grass carp judged from SGR and gill Na+-K+ ATPase activity is 5.38 and 7.41 g kg−1 diet, respectively. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was carried out to investigate the effect of dietary glutamate (Glu) supplementation on growth performance, digestive enzyme activities and intestinal antioxidant capacity of grass carp ( Ctenopharyngodon idella). A total of 540 grass carp with average initial weight of 370 ± 3.8 g were fed three diets supplemented with 0, 8 and 16 g kg−1 Glu. The per cent weight gain, specific growth rate, feed conversion ratio, and protein and lipid productive value were significantly improved by dietary Glu supplementation. Feed intake, condition factor, visceral somatic index and perivisceral fat ratio were not significantly different between dietary groups. Hepatosomatic index, intestinal somatic index, intestine length index, intestine protein content, trypsin activity in hepatopancreas and intestine, lipase activity in proximal and mid-intestine (MI) and hepatopancreas, alkaline phosphatase and gamma-glutamyl transpeptidase activities in intestine, creatine kinase activities in the mid- and distal intestine, intestinal folds height in the proximal and MI were significantly increased with increased Glu. Malondialdehyde and protein carbonyl contents in the intestine decreased with increased Glu. Superoxide anion and hydroxyl radical scavenging ability, glutathione reducase, catalase and total superoxide dismutase activities, and glutathione content in the intestine were increased with increased Glu. These results suggested that dietary Glu supplementation increased intestinal antioxidant capacity, digestive and absorptive ability and improved fish growth. [ABSTRACT FROM AUTHOR]

Grass carp ( Ctenopharyngodon idella) is a valuable aquacultural species in China, but it is highly vulnerable to infectious diseases, which consequently may cause tremendous economical loss. To reduce the risk of disease in the fish, antibiotics have been used in the fish diet, which in turn caused some negative effects on human health. In this study, we choose lactosucrose ( LS) as antibiotic alternative added to the diet of the grass carp juveniles and then to evaluate the effects of 15 g Kg−1 LS in the diet on the gene transcript profiles. After the trial for 56 days, we observed that the weight gain rate, specific gain rate and feed conversion rate were increased by 14.2%, 9.2% and 10.1%, respectively, in the trial group compared with the control group. The gene expression levels in the liver tissues of grass carps were assayed using the zebrafish c DNA microarray technology and real-time RT- PCR. Comparing with the control group, 416 genes were identified, and among them, 266 genes were up-regulated and 150 were down-regulated on the trial group. Among the up-regulated genes selected, most of them related to growth, immune reaction and sugar metabolism. Most of the down-regulated genes are RAS oncogene family members, V-myc viral oncogene homologue and programmed cell death-related factors. The apparent regulation of gene expression stimulated by LS suggests that the potential application of the LS in improving the growth performance and immunity on the grass carps. Together, this study provides convincing data in support of the use of LS as an alternative dietary antibiotic in fish. [ABSTRACT FROM AUTHOR]

In the present study, it was examined whether variability in chemical composition of different cottonseed (Nazilli-M39, Nazilli-84 and Çukurova-1518) meals (CSMs) and sunflower (Sanbro, Isera and Coban) meals (SFMs) had any effects on digestibility when fed to grass carp. Protein and energy digestibility of CSMs (83.2-86.8%; 88.7-92.5%) and SFMs (78.9-83.1%; 88.4-92%) had a coefficient of variation of 1.96% (CSMs) and 1.52% (SFMs) for protein and 1.93% (CSMs) and 1.82% (SFMs) for energy digestibility. Sum of amino acids digestibility of CSMs (83.1-86.5%) and SFMs (78.9-83.4%) had a coefficient of variation of 1.85% and 2.47%, respectively. Protein and energy digestibility of CSMs and SFMs was significantly positive affected by a range of compositional features including protein or sum of amino acids and phosphorus content, and significantly negative affected by fiber and carbohydrate contents in the test ingredients. This suggested that fiber and carbohydrate contents of CSMs and SFMs may also be influencing the nutritional value of its own protein or sum of amino acids. In conclusion, the relationship between plant protein meals protein content and its digestible value provides a good support for the development of a system of grain segregation by protein content and ingredient pricing according to that protein content. [ABSTRACT FROM AUTHOR]

In the uplands of northern Vietnam, culture of grass carp contributes significantly to income and household food security of Black Thai farmers. Maize is one of the most important upland crops and barnyard grass is the most important weed in the paddy rice fields. Thus, these are frequently used by small-scale fish farmers as fish feed. An 8-week feeding trial was conducted simultaneously in a recirculation and in a respirometric system to determine the digestibility and metabolizability of the nutrients of maize leaves and barnyard grass, to assess their crude protein, lipid and energy conversion and to estimate the energy allocation in grass carp. The following diets were used: diet ‘A’ (reference diet) containing 39% crude protein with 19.8 MJ kg−1 gross energy; diets ‘B’, ‘C’ and ‘D’, which contained the same amount of the reference diet as the control diet, supplemented with a known amount of dried barnyard grass, dried maize leaves or fresh maize leaves, respectively. Five fish were assigned to each treatment in each experimental unit. Reference and test diets were fed to fish and faecal samples were collected and the oxygen consumption was measured in order to set up an energy budget of the fish over the whole experimental period. The weekly development of the body weight was recorded. The body weight gain of the fish fed diet D was significantly higher than that of the group fed diet A, which also in turn was significantly higher than that of fish fed diet B or C. The apparent digestibility coefficients (ADC) of nutrients and gross energy for the different experimental diets in fish kept in the aquaria were, for diets A, B, C and D respectively, 94.1%, 60.9%, 70.5% and 84.7% for protein, 91.3%, 60.7%, 76.8% and 71.8% for lipid; 95.9%, 44.5%, 60.6% and 69.1% for gross energy. The partial ADC of plant leaf ingredients were determined and barnyard grass and dried maize leaves were found to be not only poorly digestible but having negative impact on the digestibility of the reference diet, while fresh maize leaves were well digested. The results of the present study indicated that fresh maize leaves have a good potential to be used as supplement in diets for grass carp. [ABSTRACT FROM AUTHOR]

Six isonitrogenous (390 g kg−1) and isoenergetic (16.2 kJ g−1) diets with varying carbohydrate : lipid (CHO : L) ratios (202.5–1.74), were fed to triplicate groups of 25 fish in indoor recirculation system. Over 8-week-growth trial, best weight gain (WG), specific growth rate, feed conversion ratio, protein efficiency ratio and protein production value ( P < 0.05) were observed in fish-fed diets with CHO : L ratio of 7.5. Fish fed either the lowest (1.7) or highest (202.5) CHO : L ratio tended to produce lower ( P < 0.05) growth and feed conversion efficiencies. The values of viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio increased as dietary CHO : L ratios decreased. There were no significant differences in whole body and liver crude protein among dietary treatments. Whole body and liver lipid increased as CHO : L ratios decreased. Plasma cholesterol and triacylglyceride levels increased linearly as dietary CHO : L ratios decreased. Activities of glucokinase and pyruvate kinase were stimulated by elevated levels of dietary carbohydrate; however, activities of lipase (LPS) and alkaline phosphatase were stimulated by elevated levels of dietary lipid. Based on a second-order polynomial regression analysis of WG against dietary carbohydrate and lipid levels, 275 g kg−1 of carbohydrate and 59 g kg−1 of lipid, corresponding to a CHO : L ratio of 4.7, in a diet holding 390 g kg−1 of crude protein and 16.3 kJ g−1 of gross energy, proved to be optimal for grass carp. These results indicated that utilization of dietary lipid and carbohydrate was moderate in grass carp, but the fish were a little more capable of utilizing lipid compared with carbohydrate. [ABSTRACT FROM AUTHOR]

A series of studies based on biochemical assays and electrophoretical observations has been conducted in order to investigate activity distributions and partially characterize various types of proteinases in the digestive tract of grass carp, Ctenopharyngodon idella (Val.). The casein digestion assays revealed that the presence of acidic proteinase had the highest activity at pH 2.5–3.0 and the alkaline proteinases at pH 10.0. The acidic proteinase activity distribution was found to decrease gradually from the oesophagus to the anus. Pepstatin A and EDTA inhibited the acidic proteinases activity. The SDS-substrate-PAGE showed that crude extraction of grass carp intestine contained an acidic proteinase active component with molecular mass of 28.5 ku. The substrate-PAGE at neutral pH condition showed the presence of two acidic proteinase active components. The activity distribution of alkaline proteinase was found to slightly fluctuate along the intestine. And the whole intestine had very high activity. The inhibition assays and substrate specificity assays showed that trypsin was the main active component of the alkaline proteinases. The SDS-substrate-PAGE further showed that the crude extraction of grass carp intestine had four types of alkaline proteinase with molecular mass of 26.4, 30.8, 43.0 and 105.0 ku respectively. They were characterized to be trypsin (26.4, 30.8 and 43.0 ku) and un-serine proteinase (105.0 ku) respectively. No chymotrypsin was detected. [ABSTRACT FROM AUTHOR]

Herbivorous grass carp ( Ctenopharyngodon idella) has been reported to exhibit low capacity to utilize high dietary lipid, but different lipid sources might affect this limited capacity. In order to compare the effects of different lipid sources with different lipid levels, juvenile grass carp were fed one of nine diets containing three oils [lard, plant oil mixed by maize and linseed oil, and n-3 high unsaturated fatty acid-enriched (HUFA-enriched) fish oil] at three lipid levels (20, 60 and 100 g kg−1 dry diet) for 8 weeks. Decreased feed intake, poor growth performance, hepatic pathology and higher blood lipid peroxidation were found in 60 and 100 g kg−1 fish oil groups. Conversely, in lard and plant oil groups, even at 100 g kg−1 dietary lipid level, feed intake and growth performance did not decrease, despite histological observation revealed hepatic pathology in these groups. Plasma triglyceride and cholesterol contents increased significantly in all 100 g kg−1 dietary lipid groups. In the comparison of hepatic FA β-oxidation among three oil groups at 60 g kg−1 dietary lipid level, impaired mitochondrial and peroxisomal FA oxidation capacity was observed in fish oil group. The results confirmed the relatively low capacity of grass carp to utilize high dietary lipid, and furthermore excess HUFA intake will result in more serious adverse effects than other FA. [ABSTRACT FROM AUTHOR]

A study was undertaken to determine the effect of dietary lipid level on growth, feed efficiency and body chemical composition of juvenile grass carp. Seven isonitrogenous diets (400 g kg−1 crude protein) containing seven dietary lipid level (0, 20, 40, 60, 80, 100 and 120 g kg−1 dry matter) were fed to triplicate groups of 40 fish with initial weight 6.52 g, for 70 days. No obvious and assured essential fatty acid deficiency symptom appeared in fish fed the lipid-free diet. Excess dietary lipid level (100 and 120 g kg−1) resulted in decreased feed intake. The best growth performance and feed utilization was observed in fish fed 20–40 g kg−1 dietary lipid. The fish fed a lipid-free diet had the lowest protein efficiency and protein retention. Growth performance and feed utilization increased with the increasing dietary lipid levels up to 40 g kg−1 dietary lipid. Higher dietary level (above 40 g kg−1) made growth performance and feed utilization decrease and no protein sparing effect was observed. Lipid retention decreased as dietary lipid level increased. Mesenteric fat index (MFI) increased, hepatosomatic index (HSI) decreased with dietary lipid level. The increased MFI and simultaneous decrease lipid retention can be explained by differences in growth. The effect of dietary lipid levels on the chemical composition of tissues was significant only for whole body and muscle. The excess lipid content of liver in all groups was regarded as a slight symptom of fatty liver, which was partly identified by microscopic structural study and lower plasma lipid indexes, comparing to the initial plasma data. In conclusion, grass carp is a fish with low energy requirement and excess dietary lipid level should be avoided. [ABSTRACT FROM AUTHOR]