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To determine the impact of replacing fish meal (FM) in the diet with various levels of soybean meal (SBM) on the spotted knifejaw Oplegnathus punctatus, a 56 day feeding trial was done. Seven diets were formulated with SBM to replace 0% (SBM0), 30% (SBM30), 40% (SBM40), 50% (SBM50), 60% (SBM60), and 70% (SBM70) of FM protein, and SBM50 + T was developed on the basis of SBM50 with the addition of 1.2% taurine. There were triplicate groups of 18 fish (initial weight: 14.62 ± 0.02 g). The weight gain (WG), specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER) values of the SBM0, SBM30, and SBM50 + T groups were found to be significantly higher than those of the SBM60 and SBM70 groups (p < 0.05). The daily energy gain (DEG), daily nitrogen gain (DNG), daily lipid gain (DLG), energy retention (ER), nitrogen retention (NR), and lipid retention (LR) values decreased significantly with increasing dietary SBM levels (p < 0.05). The highest retention of most amino acids (except lysine) was observed in the SBM30 group (p < 0.05). The lipid content of the whole body and dorsal muscle decreased significantly as dietary SBM levels increased (p < 0.05). Fish fed the SBM70 diet had the lowest serum triglyceride (TG) concentrations (p < 0.05). The effects of different treatments on total cholesterol (T-CHO) were not significant (p > 0.05). Fish fed the SBM0 and SBM30 diets had the highest amylase (AMS) and lipase (LPS) activities (p < 0.05). The lowest liver superoxide dismutase (SOD) and catalase (CAT) activities were observed in the SBM70 group. The malondialdehyde (MDA) concentration of the SBM50 to SBM70 groups were significantly higher than that of other groups (p < 0.05). The levels of interleukin 8 (il-8) mRNA were highest in fish fed the SBM0, SBM30, and SBM50 + T diets (p < 0.05), while the level of transforming growth factor β1 (tgf-β1) was the opposite (p < 0.05). According to the broken line regression of WG and FE, the highest level of FM substitution by SBM for Oplegnathus punctatus was 24.07–25.31%. [ABSTRACT FROM AUTHOR]

Abstract: A 57‐day growth experiment was conducted with juvenile gibel carp (13.48 ± 0.10 g) in a flow‐through system to study the effect of dietary phosphorus on growth performance, body composition, nutrition utilization, phosphorus loading and enzymes activities. Seven semipurifed diets were formulated to contain 0.07 (the basal), 2.27, 5.32, 8.10, 12.06, 15.24 and 19.48 g available phosphorus/kg diet. The results showed that specific growth rate, body length and feed efficiency significantly increased in the fish fed diets containing 0.07 to 15.24 g available P/kg diet (p < .05). Ash and P content increased in fish fed diets containing 0.07–12.06 P g/kg (p < .05) and then levelled off, while moisture, crude protein and lipid had no significant difference (p > .05). The protein retention efficiency increased in the fish fed with diets 0.07–5.32 g/kg P (p < .05) and then reached a plateau. The P content in faeces was higher in fish fed diets containing 15.24 and 19.48 g available P/kg. Total P concentration in tank water increased in fish fed 0.07–12.06 g available P per kg diet (p < .05). The plasma P was higher in the fish fed with 15.24 g available P/kg diet (p < .05), triglycerides was lower in the fish fed diet containing 15.24 and 19.48 g available P/kg (p < .05), no significant differences were observed in plasma Ca, plasma glucose and calcitonin (p > .05). Based on SGR, whole body P content and FE, dietary available P requirement for juvenile gibel carp were 13.37, 13.97 g/kg and 15.06 respectively. [ABSTRACT FROM AUTHOR]

A 106-day growth trial was executed in a flow-through system to investigate the effects of dietary vitamin A on growth, hematological indices, digestive functions, body composition and lipid metabolism of on-growing gibel carp (69.39 ± 0.08 g). Fish were randomly assigned to seven groups and fed with different diets containing 273, 1278, 1962, 3155, 4105, 4931 and 5751 IU vitamin A kg − 1 , respectively. Specific growth rate (SGR) and feed efficiency (FE) of gibel carp were lower at 273 and 5751 IU kg − 1 vitamin A levels ( P < 0.05). Hemoglobin content in blood, and the levels of plasma growth hormone (GH) and insulin-like growth factor I (IGF-1) were not significantly influenced by dietary vitamin A ( P > 0.05). Although the apparent digestibility coefficients (ADCs) of dry matter, crude protein, crude lipid and energy were not influenced significantly ( P > 0.05), high dietary vitamin A (5751 IU kg − 1 ) decreased the activity of intestinal Na + –K + ATPase ( P < 0.05). The plasma total antioxidative capacity (T-AOC) was improved at the levels of 1962 and 3155 IU vitamin A kg − 1 ( P < 0.05). Vitamin A deficiency increased the activities of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ( P < 0.05), and decreased the contents of whole body and liver crude lipid and the plasma cholesterol content ( P < 0.05). Plasma cholesterol and vitamin A contents were significantly increased ( P < 0.05) and then leveled off with the increasing of dietary vitamin A level. Broken-line regression between dietary vitamin A level and plasma cholesterol content or plasma vitamin A content indicated that the dietary vitamin A requirement of on-growing gibel carp was to be approximately 1716 IU kg − 1 and 2698 IU kg − 1 , respectively. 2698 IU vitamin A kg − 1 diet is recommended for on-growing gibel carp in the present study. [ABSTRACT FROM AUTHOR]

Spirulina, Arthrospira platensis , contains high levels of protein and lutein. To evaluate nutritional, pigmentation, and antioxidation effects of A. platensis , a total of 900 juvenile yellow catfish (Pelteobagrus fulvidraco) were divided into 18 tanks (3 tanks/treatment, 50 fish/tank) and fed a diet supplemented with A. platensis for 50 days. A. platensis was used in quantities of 0, 57.6, 115.1, 172.7, 230.3, and 287.9 g kg−1 for experimental diets to replace fishmeal protein at levels of 0 (AP0), 20% (AP20), 40% (AP40), 60% (AP60), 80% (AP80), and 100% (AP100). Results revealed that substituting up to 80% of fishmeal by A. platensis biomass did not have a negative effect on fish growth, feed utilization, or apparent digestibility. However, significantly lower growth rates were observed when 100% of the fishmeal was substituted (P < 0.05). A. platensis replacement groups led to an increase in skin yellowness and dose-dependent enrichments of total lutein in dorsal skin, abdominal skin, and liver tissues (P < 0.05). There were similar enhancements observed in glutathione concentrations and glutathione peroxidase activities in plasma and liver (P < 0.05). Analyses based on lutein concentration between abdominal skin and experimental diets revealed that the optimal substitution amount was 72.03% (207.4 g kg−1 of A. platensis), which could ensure growth and pigmentation in yellow catfish. • Arthrospira platensis can be used as alternative source of fish meal in yellow catfish diets. • Arthrospira platensis could increase the lutein contents to enhance the yellowness in skin of yellow catfish. • The quality was improved of yellow catfish because the A. platensis enhanced the pigmentation and antioxidant abilities. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was designed to investigate the effect of different dietary lysine (Lys) levels on the growth, molting, lipid metabolism, antioxidant, and immunity of postlarva Scylla paramosain. Six diets with 1.20%, 1.46%, 1.84%, 2.06%, 2.35%, and 2.67% Lys levels (dry matter) were formulated and experimented on the postlarva Scylla paramamosain. The results showed that Scylla paramamosain fed with the 2.06% lysine obtained the highest growth performance and the highest molting frequency. Appropriate dietary Lys levels (1.73–2.03%) can improve the antioxidant capacity of Scylla paramamosain. Although unaffected by dietary Lys, the whole-body lipid content of the 1.20% Lys group was numerically higher than those of the 1.46–2.67% Lys groups. The variation in whole-body crude protein content showed a similar trend with those in the content of EAA and NEAAs, with the highest whole-body crude protein content appearing in the 2.06% Lys group. The crabs obtained the highest expression of igf , fas , EcR and fabp genes in the 2.06% Lys group. When dietary Lys levels were > 1.20%, the transcription level of immune related-genes increased. As suggested by the results of the second order polynomial regression analysis of weight gain, the Lys requirement of postlarva Scylla paramamosain is 2.03% (4.51% of dietary protein). • The optimal dietary lysine level for postlaval S.paramamosain was 2.03% (4.51% of the dietary protein). • This study indicates that appropriate dietary lysine can promote the expression of lipid metabolism genes in this species. • This study indicates that appropriate dietary lysine can promote protein synthesis in this species. • This study indicated that an adequate lysine content in diet can improve the health of postlaval S. paramamosain. [ABSTRACT FROM AUTHOR]

Abstract The effects of guar gum, when used as a feed binder, on growth performance, digestive enzyme activity, and intestinal histology in gibel carp were evaluated. Four isonitrogenous and isoenergetic diets were formulated and supplemented with 0%, 1%, 3%, and 5% guar gum. The different diets were fed to triplicate groups of gibel carp (mean initial weight: 5.60 ± 0.003 g) for 51 d. Feed supplemented with 1% guar gum had no effect on specific growth rate, feed efficiency, condition factor, or protein retention efficiency as compared to the control group; this level of supplementation increased microvillus length in the distal intestine and increased fecal viscosity. In contrast, 5% guar gum supplementation increased feed hardness, decreased feed water solubility, and decreased total nitrogen content in the soaking water after 3-h immersion. However, 5% guar gum supplementation decreased feed intake and induced distal intestine damage, as indicated by shorter microvilli as compared to the control group. Supplementation with 5% guar gum also decreased the activity levels of intestinal digestive enzymes (chymotrypsin, amylase, and alkaline phosphatase) and decreased plasma total cholesterol and triglycerides, and finally reduced fish growth. Dietary supplementation with 1% guar gum increased fecal viscosity sufficiently to decrease water pollution, without significant adverse effects on growth performance, feed utilization, and intestinal microstructure in the gibel carp. Highlights • Diets supplemented with 5% guar gum decreased gibel carp growth. • Diets supplemented with 5% guar gum damaged gibel carp intestinal structure. • Optimal guar gum supplementation level in the gibel carp was 1%. [ABSTRACT FROM AUTHOR]

It is well known that most fish would prefer to use body lipid stores for energy expenditure when receiving a long-term food restriction. However, the mechanism of this is still not clear. In the present study, a growth experiment was carried out to investigate the effects of food restriction on growth performance, gene expression related in regulation of lipid metabolism and food ingestion in grass carp ( Ctenopharyngodon idellus ). Four rations, satiation (S), 80% S, 60% S and 40% S, were adopted in this study. Each treatment was randomly assigned to triplicate net cages of 15 fish (177.3 ± 3.3 g) per cage. The experiment lasted for 49 days at 30.0 ± 3.0 °C. The experimental results showed that a significant increase in feeding rate and weight gain was found in grass carp with the increased ration level. The body lipid and energy content of the grass carp exhibited a significant decrease when receiving food restriction. The transcriptional levels of the genes involved in lipogenesis ( srebp -1 c , fas , pparγ ) were down-regulated at the rations of food restriction. The relative expression of hepatic fas (fatty acid synthetase) and srebp -1 c (sterol regulatory element-binding protein 1c) in the fish at satiation were significantly higher than the restricted-fed groups. Similarly, the expressions of hepatic pparγ (peroxisome proliferator-activated receptor-γ) in the fish at the ration of satiation and 80% S were significantly higher than the group at the low ration of 40% S. However, the expression of hepatic cpt -1 a (carnitine palmitoyl transferase I) involved in fatty acid β-oxidation in fish was significantly up-regulated when receiving food restriction. Other hepatic lipolysis genes of pparα (peroxisome proliferators-activated receptor α) and hl (hepatic lipase) didn't show any significant changes in restricted-fed fish. The transcriptional levels of hepatic leptin and hypothalamus pomc (proopiomelanocortin) were significantly down-regulated in fish fed with restricted rations. But the hypothalamus npy (neuropeptide Y) and lepr (leptin receptor) had no change. The present results indicated that a long-term food restriction could cause less accumulation of lipid and could be through a way of down-regulating lipogenesis genes and up-regulating lipolysis genes. Long-term restriction could also activate the appetite of grass carp by down-regulating some anorexigenic genes. Statement of relevance Food restriction for some time could lead to a suitable lipid storage, in case of accumulation of fatty acid profile and lipid, in cultured grass carp. [ABSTRACT FROM AUTHOR]

Five semi-purified diets were formulated with varying crude protein (CP) level (ranging from 20.77 to 45.69%) to assess the dietary protein requirement of juvenile bluegill sunfish ( Lepomis macrochirus ). Each diet was given to triplicate groups (20 fish per group, 1.20 g per fish) for 10 weeks. In this study, the weight gain (WG) values showed a general increasing trend with increasing dietary CP level up to 40.23%, and then no further improvement of growth was observed with further increase in dietary CP level. In addition, feed efficiency (FE) also improved with increase in dietary CP level; the maximum value was observed in fish fed diet with 40.23% CP. Besides, fish fed diets with 20.77 and 28.16% CP had significant higher daily feed intake (DFI) and lower energy retention (ER), lipid retention (LR) and nitrogen retention (NR) values than other treatments ( P < 0.05). Moreover, fish fed 20.77% CP diet with the highest starch content showed the highest hepatosomatic index (HSI) and relatively higher liver glycogen content than other groups. However, no significant difference in liver lipid content was observed among all dietary treatments. Fish fed diets with 20.77 and 28.16% CP had a relatively lower whole body protein and dorsal muscle protein content than other treatments. Based on broken-line regression analysis, the optimal dietary protein content for sunfish is about 41.51 to 42.37%. Statement of Relevance The main aim of this study is to quantify the optimum amount of dietary protein for juvenile bluegill sunfish ( L. macrochirus ). The research outcomes will develop formulated diets for L. macrochirus and will have good potential of being commercialized. [ABSTRACT FROM AUTHOR]

Six isoproteic and isolipidic diets were designated to investigate the effects of dietary carbohydrate level (from 0% to 30%) on growth performance, feed utilization and body composition of juvenile grouper Epinephelus akaara (initially weighing, 7.79 ± 0.01 g/fish). Each diet was given to triplicate groups (20 juvenile grouper per cage) for 8-weeks. The weight gain (WG) and final body weight (FBW) were quadratically and linearly related to the increase of dietary carbohydrate level ( P < 0.05). The weight gain (WG) values increased with increasing dietary carbohydrate from 0% to 6% while at higher levels WG values decreased. Feed conversion ratio (FCR), protein efficiency ratio (PER) and daily feed intake (DFI) were found to be not significantly related to the dietary carbohydrate ( P > 0.05). As the level of dietary carbohydrate increased both quadratic and linear responses were observed on the intraperitoneal fat ratio (IPF). The whole body and muscle lipid content were relatively lower in fish fed the 30% dietary carbohydrate diet compared with the other treatments. Liver glycogen content generally increased with increasing dietary carbohydrate levels. Energy retention (ER) and lipid retention (LR) decreased significantly with increasing dietary carbohydrate levels. Based on second-order polynomial regression analysis of WG, this study suggests that 7.64% dietary carbohydrate level provides a maximum growth for juvenile E. akaara. Statement of relevance The main aim of this study is to determine the effects of dietary carbohydrate levels on growth performance, feed utilization and body composition of juvenile E. akaara . The research outcomes will develop formulated diets for E. akaara and will have good potential of being commercialized [ABSTRACT FROM AUTHOR]

A 56-day growth experiment was conducted in net cages to investigate the dietary arginine requirement in two sizes of gibel carp using diets containing casein and precoated crystalline amino acids (CAA) as the main protein sources. Six isonitrogenous and isoenergetic (310 g crude protein and 16.8 MJ gross energy kg − 1 dry matter) diets containing graded levels of arginine from 5.4 to 26.6 g kg − 1 dry matter were prepared. Triplicates of 30 fish (body weight 51.6 ± 0.3 g) or 20 fish (body weight 147.8 ± 0.5 g) were fed to apparent satiation with one of six experimental diets by hand four times a day. Specific growth rate (SGR) and feed efficiency (FE) significantly increased with the increase of dietary arginine levels from 5.4 to 17.6 g kg − 1 (small fish) or from 5.4 to 13.0 g kg − 1 (big fish), and thereafter, kept constant. In the fish of two sizes, with increasing of dietary arginine level, whole body and dorsal muscle protein content first significantly increased, and then reached a plateau or slightly declined. Protein retention efficiency (PRE) showed the same trend with protein content in big fish, but not in small fish. Muscle arginine contents markedly increased with increasing dietary arginine level in two sizes of fish. Growth hormone (GH), insulin like growth factor-I (IGF-I) and nitro oxide (NO) concentrations in plasma, and NO synthase (T-NOS), arginase activities in liver were affected by dietary arginine levels, while plasma ammonia, urea concentration and hepatic alanine aminotransferase (ALT), aspartate aminotransferase (AST) activities had no significant differences in the fish of two sizes. TOR, S6K1 and IGF-I mRNA in liver or muscle of 5.4 g kg − 1 group significantly down-regulated, but no differences were found for 4E-BP2 mRNA levels in the fish of two sizes. Pituitary GH mRNA significantly up-regulated with increasing dietary arginine level in small fish, but not in big fish. For the fish of two sizes, significant differences were found in all indices mentioned above except for plasma urea, hepatic ALT and AST. Broken-line regression analysis of SGR demonstrated that dietary arginine requirement for gibel carp of these two sizes were 16.4 (small fish) and 12.9 g kg − 1 (big fish) of dry matter, corresponding to 53 and 42 g kg − 1 of dietary protein, respectively. [ABSTRACT FROM AUTHOR]

A 60-day growth trial was conducted to investigate the effect of dietary protein levels on growth performance, digestive enzyme activities, transaminase activities and GH-IGF-I axis gene expression of broodstock gibel carp (initial body weight, 180.3 ± 0.4 g) using diets containing white fishmeal and casein as the main protein sources. Six isolipidic (100 g kg − 1 ) and isoenergetic (gross energy 17.5 kJ g − 1 ) diets were prepared, with protein levels ranging from 200 to 400 g kg − 1 at 40 g kg − 1 increments. Each diet was fed by hand to triplicate groups of 22 fish each to apparent satiation four times a day. Results indicated that specific growth rate (SGR), feed efficiency (FE) and protein retention efficiency (PRE) significantly increased with the increase of dietary protein levels from 200 to 360 g kg − 1 , after that, SGR and FE plateaued while PRE notably decreased. Whole-body and muscle crude lipid increased and moisture decreased with increasing dietary protein levels; whereas crude protein and ash in whole-body and muscle, condition factor, vicerosomatic index and hepatosomatic index showed no obvious differences between treatments. Plasma ammonia concentration, hepatic alanine transaminase and aspartate transaminase activities markedly enhanced with the increase of dietary protein level up to 320–360 g kg − 1 . Intestinal trypsin activity peaked in fish fed protein level of 320 g kg − 1 , and then remarkably descended; while no significant differences were observed in intestinal lipase and α-amylase. The relative mRNA abundance of insulin like growth factor-I (IGF-I) in liver notably up-regulated with dietary protein level increasing to 360 g kg − 1 , and down-regulated at higher protein level. Pituitary growth hormone (GH) mRNA showed an almost opposite trend with IGF-I. In conclusion, based on a broken-line analysis of SGR, the recommended dietary protein level for broodstock gibel carp was 369 g kg − 1 , which was higher than that for sub-adult fish. Statement of relevance This study provides basic data of nutritional requirement for broodstock gibel carp. [ABSTRACT FROM AUTHOR]

Abstract: A 12-week growth trial was conducted in a flow-through system to investigate the chronic toxic effect of dietary intake of cyanobacteria on growth, feed utilization and microcystins accumulation in Nile tilapia (Oreochromis niloticus L.) (initial body weight: 5.6 g). Six isonitrogenous and isocaloric diets were formulated to include different contents of cyanobacteria with the dietary microcystins increasing from 0 to 5460.06 ng/g diet. The results showed that dietary intake of cyanobacteria could increase the growth of tilapia while there are no impacts on feed conversion efficiency or mortality. Feeding rate was higher for the diets containing highest cyanobacteria. Microcystins were mostly accumulated in fish liver. The relationship between microcystins contents in muscle, liver, spleen and dietary intake could be described by quadratic equations. Microcystins content in the muscle of Nile tilapia in present study exceeded the upper limit of the tolerable daily intake (TDI) of microcystins suggested by the WHO (0.04 μg/kg body weight/d). It is suggested that Nile tilapia fed on toxic cyanobacteria is not suitable for human food. [Copyright &y& Elsevier]

This study estimated the effects of different dietary carbohydrate levels on growth performance, feed utilization, body composition, and the gene expression of key enzymes involved in hepatopancreas lipogenesis and glucose metabolism in mud crab Scylla paramamosain. Crabs with an initial mean weight of 1.84 ± 0.06 g were used in an 8-week experiment to test five diets (C6, C12, C18, C24, C30) formulated to contain increasing levels of carbohydrate, measured as 8.55%, 13.36%, 17.76%, 25.64% and 32.50%, respectively. The results showed that the levels 25.64% and 32.50% improved growth performance, with the best gains at 25.64%. The highest dietary carbohydrate level led to higher hemolymph glucose concentrations and more fat deposition in the body. Furthermore, real-time quantitative PCR analysis revealed that the mRNA expression of key enzymes in glycolytic and lipogenic metabolism (i.e. glucokinase, fructose-2,6-diphosphatase, and fatty acid synthetase) were significantly affected by the dietary carbohydrate level. The mRNA expression of glucokinase was lowest in the group fed the carbohydrate-rich C30 diet, and the mRNA of fructose-2 and 6-diphosphatase were remarkably expressed in the C24 group (P <.05). The mRNA expression of fatty acid synthase at the dietary carbohydrate levels 32.50% and 25.64% were respectively 10-fold and 5-fold greater than with 8.55% dietary carbohydrate. The overall data suggest that S. paramamosain can be fed 25.64%–32.50% carbohydrate to achieve satisfactory growth performance. A two-slope broken-line regression analysis of weight gain showed that 24.08% dietary carbohydrate would be optimal for this species reared under similar conditions. • Appropriate diet carbohydrate level improved the mud crab Scylla paramamosain growth performance, and 24.08% is optimal. • The mud crab S. paramamosain may endure high carbohydrate level without death, but excess dietary carbohydrate resulted in higher blood glucose and fat deposition in the body. • Adding appropriate diet carbohydrate level improved the mud crab growth performance. • Excess dietary carbohydrate resulted in higher blood glucose and fat deposition in the body of mud crab. [ABSTRACT FROM AUTHOR]