Effects of dietary coated protease on growth performance,feed utilization,nutrient apparent digestibility,intestinal and hepatopancreas structure in juvenile Gibel carp (Carassius auratus gibelio)

This study was conducted to investigate the effects of dietary protease on growth performance, feed utilization, whole‐body proximate composition, nutrient digestibility, intestinal and hepatopancreas structure of juvenile Gibel carp, Carassius auratus gibelio (mean weight 8.08 ± 0.18 g). Six diets were prepared, including a positive control diet (dietary protein 350 g/kg, PC), one negative control diet (dietary protein 33 g/kg, NC) and four protease supplementations diets, which were 75, 150, 300 and 600 mg/kg protease NC diet. After 12 weeks of diet feeding in indoor recycle aquarium tanks, no significant difference (p > .05) was found on growth performance between fish fed diet with 75–600 mg/kg protease and the PC group. Compared with the fish fed the NC diet, the specific growth rate of fish fed 300 mg/kg protease increased significantly (p < .05), as well as protein efficiency ratios (p < .05), while feed conversion was the opposite (p < .05). The nutrient digestibility of crude protein and lipid was higher (p < .05) in fish fed 150 mg/kg protease diet than the PC diet. Whole‐body proximate composition of fish was not affected (p > .05) by the dietary treatment. Serum alkaline phosphatase and albumin were significantly affected by dietary protease (p < .05), while the content of total protein, glucose, triglyceride, total cholesterol, aspartate aminotransferase and alanine aminotransferase activities in serum was not affected (p > .05). Foregut muscular thickness was thinner (p < .05), when the fish fed diets supplementation of protease in 150 or 600 mg/kg diet than the NC diet. Protease activities in hepatopancreas and foregut were higher (p < .05), in the fish fed 150 or 300 mg/kg protease diet than the fish fed the PC diet, but those in the mid‐ and hindgut were not significantly affected (p > .05) by the dietary treatments. Based on the regression analysis of weight gain rate, the optimal dietary inclusion level of protease was 400 mg/kg in the diet for juvenile Carassius auratus gibelio.     

Effects of dietary vitamin C on growth,gonad development and antioxidant ability of on‐growing gibel carp (Carassius auratus gibelio var. CAS III)

An 88‐day experiment was conducted in a flowing system to evaluate the effects of dietary vitamin C on growth, body composition, antioxidant and gonad development of on‐growing gibel carp. Triplicate tanks of gibel carp (77.2 ± 0.1 g) were randomly fed with one of seven experimental diets containing l ‐ascorbic acid of 0, 101.1, 188.5, 313.1, 444.1, 582.1 and 747.0 mg/kg, respectively. The results showed that specific growth rate (SGR) and feed efficiency (FE) of fish were not affected by dietary l ‐ascorbic acid. Dietary l ‐ascorbic acid of 444.1 mg/kg diet led to low levels (p < .05) of gonadosomatic index (GSI) and hypothalamic gonadotropin‐releasing hormone (GnRH) in on‐growing fish, as well as the early ovarian stages (Developing stages) compared with fish (Maturing stages) from the other groups. Dietary l ‐ascorbic acid supplementation increased (p < .05) the dorsal muscle collagen content, but did not affect the protein or lipid content of dorsal muscle in gibel carp. Plasma total antioxidant capacity (T‐AOC) and superoxide dismutase (SOD) activity increased (p < .05) and then remained unchanged with the increase in dietary l ‐ascorbic acid levels. Dietary l ‐ascorbic acid of 101.1 mg/kg diet improved (p < .05) plasma lysozyme activity of the fish. Broken‐line regression indicated that dietary l ‐ascorbic acid requirement of 77 g gibel carp was 223.3 or 225.0 mg/kg diet based on plasma T‐AOC or SOD activity, which was a little higher than that based on plasma l ‐ascorbic acid concentration (193.2 mg/kg).     

Replacing fish meal with a blend of poultry by‐product meal and feather meal in diets for giant croaker (Nibea japonica)

An 8‐week feeding trial was conducted to evaluate the potential of replacing fish meal with poultry by‐product meal (PBM) and feather meal (FEM) in giant croaker (Nibea japonica) diet. The control diet (C) contained 400 g/kg fish meal, and 20%, 40%, 60% and 80% of the fish meal in diet C was replaced by a blend of PBM and FEM (PBM: FEM = 7:3) in diets B20, B40, B60 and B80, respectively. The weight gain and feed intake of fish fed diet C did not differ from those of fish fed diets B20 and B40 (p > .05), but were higher than those of fish fed diets B60 and B80 (p < .05). Phosphorus retention efficiency was lower in fish fed diets C, B20 and B40 than in fish fed diets R60 and R80 (p < .05). No significant differences were found in feed conversion ratio, nitrogen retention efficiency, condition factor, hepatosomatic index, body composition and nitrogen waste among the treatments (p > .05). Ratio of fish meal consumption to fish production linearly declined with the decrease in dietary fish meal level. This study indicates that dietary fish meal for giant croaker could be reduced to 240 g/kg by inclusion of the blend of PBM and FEM.     

Effect of supplemental taurine on juvenile channel catfish Ictalurus punctatus growth performance

Juvenile channel catfish (5.6 g/fish) were fed a basal diet that contained major protein (soybean meal, cottonseed meal) and energy (ground corn grain, wheat middlings) ingredients that were derived from plant sources. The basal diet was supplemented with three levels of crystalline taurine to provide 1, 2 and 5 g/kg taurine. In addition, a fifth diet that contained 80 g/kg menhaden fishmeal formulated with the same plant‐source ingredients was included as the positive control diet. Fish were fed the five diets once daily for 12 weeks. Weight gain was highest in catfish fed taurine at 2 g/kg (47.8 g/fish) compared to catfish fed the control basal diet (40.8 g/fish) and 80 g/kg fishmeal diet (41.1 g/fish) (p < .05). Among the taurine‐supplemented diets, weight gain was lowest in catfish fed taurine at 5 g/kg. Feed conversion ratio (FCR) was significantly improved in fish fed diets supplemented with taurine at 2 g/kg compared to all other treatments (p < .01). Survival during the growth study ranged from 98.0 to 99.0% (p > .05) for all treatments. The results suggest taurine supplementation to juvenile channel catfish may improve weight gain and FCR.     

Effects of gelatin or carboxymethyl cellulose supplementation during pelleting processing on feed quality,intestinal ultrastructure and growth performance in gibel carp (Carassius gibelio)

Gelatin and carboxymethyl cellulose (CMC) were often used as binders due to their binding ability. To investigate the effects of gelatin and CMC supplementation on feed quality, intestinal ultrastructure and growth performance of gibel carp, six pelleted feed were formulated: control; supplemented with gelatin (10 g/kg, 30 g/kg and 50 g/kg); and supplemented with CMC (10 g/kg and 30 g/kg). Increased gelatin supplementation levels reduced feed solubility and pellet softening (p < .05) and decreased chemical oxygen demand in the surrounding water after pellets were immersed (p < .05). Increased levels of gelatin supplementation enhanced digesta viscosity and reduced intestinal microvilli length and digestive enzymes activities (chymotrypsin and amylase; p < .05) of fish. Fish‐fed diets supplemented with 30 g/kg gelatin had higher levels of plasma total free amino acids and glucose (p < .05) than fish fed 10 g/kg and 50 g/kg gelatin. Feed supplemented with 10 g/kg CMC were softer than those supplemented with 30 g/kg CMC (p < .05); fish‐fed diets supplemented with 10 g/kg CMC had longer intestinal microvilli (p < .05) than fish fed 30 g/kg CMC. Thus, our results indicated that either gelatin or CMC is applicable to supplement in the feed for improving feed quality and without negative effect on growth performance of gibel carp.     

Dietary supplementation of autolysed yeast enhances growth,liver functionality and intestinal morphology in African catfish

A feeding trial was conducted to evaluate the potential of dietary supplementation of autolysed brewer's yeast (AY) on African catfish. The catfish (22.5 ± 1.15 g/fish, 20 fish 33 L/tank) were fed with either of diets (390 g/kg crude protein, 140 g/kg lipid) supplemented with 0, 3, 6 or 10 g/kg AY (n = 3). After 49 days of feeding, the final body weight and metabolic growth rate of the catfish fed 3 g/kg AY (3‐AY) diet were higher than those fed the control diet (p < .05). The lowest level (p < .05) of alanine transaminase was detected in the blood of the catfish fed 3‐AY diet. The mid‐intestinal histology of the catfish revealed no significant difference (p > .05) in intestinal perimeter ratio. However, an elevated (p < .05) abundance of goblet cells and intraepithelial leucocytes were found in the intestine of catfish fed 3, 6 and 10 g/kg AY diets, with the highest level of abundance recorded in the mid‐intestine of the catfish fed 3‐AY diet. The results suggest that dietary 3 g/kg autolysed brewer's yeast supplementation improves growth performance of African catfish without deleterious effect on liver functionality and gut morphology.     

Effects of dietary lipid levels on growth,feed utilization,digestive tract enzyme activity and lipid deposition of juvenile Manchurian trout,Brachymystax lenok (Pallas)

Six isoproteic diets were designated to evaluate the effects of dietary lipid levels (from 70 to 270 g/kg) on the growth performance, feed utilization, digestive tract enzyme activity and lipid deposition of juvenile Brachymystax lenok (average initial weight 0.54 ± 0.04 g). Each diet was fed to triplicate tanks (30 fish per tank) in an indoor closed recirculating system for 9 weeks. Final body weight and weight gain were highest in fish fed 190 g/kg diet and lowest in fish fed the 70 g/kg diet. Specific growth rate of fish fed with 190 g/kg diet was significantly higher than those fed with 70 and 270 g/kg diets (p < .05). Protein efficiency ratio of fish fed with 70 g/kg diet was significantly lower than the 110–230 g/kg treatments and was not significantly different from the 270 g/kg treatment. Fish fed with 270 g/kg diet had significantly higher hepatosomatic index and viscerosomatic index than those fed with 70–190 g/kg diets (p < .05). Intraperitoneal fat ratio and the whole‐body lipid content had a trend to increase with increase in dietary lipid level. Muscle crude lipid content increased up to 190 g/kg with increase in dietary lipid level. Lipid retention decreased with increase in dietary lipid level, while no significant differences in protein intake and retention levels were observed in fish among all treatments. Lipase activity of the mixture of pyloric caeca and foregut in fish fed 190 and 230 g/kg diets was significantly higher than those fed 70 and 110 g/kg diets. Midgut and hindgut lipase activities of fish were significantly higher than those fed the 190 and 230 g/kg diets. In conclusion, based on the second‐order polynomial model of WG and FCR, this study suggested that 173.8–195.0 g/kg dietary lipid levels were appropriated for B. lenok.     

Optimum level of dietary monocalcium phosphate determined based on optimal growth and vertebrae phosphate content of juvenile Ussuri catfish,Pseudobagrus ussuriensis

Two experiments were conducted to determine the optimum level of dietary available phosphorus from monocalcium phosphate for juvenile Ussuri catfish Pseudobagrus ussuriensis. Experiment 1 was conducted to estimate phosphorus digestibility from monocalcium phosphate for juvenile Ussuri catfish. The apparent digestibility coefficient of phosphorus from monocalcium phosphate was 86.3%. In the experiment 2, triplicate groups of juvenile Ussuri catfish were fed diets containing graded levels of monocalcium phosphate (MCP: 0 g/kg, 8.2 g/kg, 16.4 g/kg, 24.6 g/kg, 32.8 g/kg and 41.0 g/kg) for 8 weeks. Fish fed the diet containing 16.4 g/kg MCP with available phosphorus of 4.8 g/kg showed the best weight gain (171.5%), feed conversion ratio (1.08) and protein efficiency ratio (2.06). No significant difference was observed in fish survival among the treatments. The best result in terms of phosphorus retention efficiency (46.10%) was observed in fish fed the diet containing 8.2 g/kg MCP with available phosphorus of 3.0 g/kg, which was not different (p > .05) from those fed the diet containing up to 24.6 g/kg MCP, and the highest vertebrae phosphorus content (58.2 g/kg) was observed in fish fed the diet containing 24.6 g/kg MCP with available P of 6.6 g/kg. The whole‐body lipid and protein, as well as phosphorus contents, were significantly affected by dietary available phosphorus (p < .05). Viscerosomatic index (VSI) and condition factor (CF) were inversely correlated with dietary phosphorus levels (p < .05). Quadratic regression analysis based on specific growth rate (SGR) against dietary available phosphorus levels indicated that the optimum available phosphorus requirement for the maximal growth of juvenile Ussuri catfish was 5.9 g/kg, and broken‐line analysis based on vertebrae phosphorus content against dietary available phosphorus levels indicated that a dietary level of 6.0 g/kg available phosphorus will provide optimum vertebrae phosphorus content.     

Effects of dietary chlorogenic acid on growth,flesh quality and serum biochemical indices of grass carp (Ctenopharyngodon idella)

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.     

Effects of Chinese herbal medicines mixture on growth performance digestive enzyme activity immune response of juvenile Japanese seabass,Lateolabrax japonicus

A single factorial experiment was conducted to investigate the effects of Chinese herbal medicines mixture (CHMM) on growth performance, digestive enzyme activity and immune response of Japanese seabass, Lateolabrax japonicus (initial weight 5.01 ± 0.32 g). The fish were fed diets containing six levels of CHMM (0, 4, 8, 12, 16 and 20 g/kg) for 4 weeks. The results showed that the weight gain rate and specific growth rate (SGR) enhanced significantly in fish fed diet containing 8 g/kg CHMM (p < .05), while the feed conversion ratio (FCR) in the 4 and 8 g/kg CHMM groups reduced significantly compared with the control (p < .05). The body crude protein levels in 8 and 16 g/kg groups were significantly higher than the control (p < .05). The pepsin, amylase and lipase activities elevated significantly in the stomach of fish fed 8 g/kg CHMM, while the erepsin and lipase in the intestine of fish in 12 and 16 g/kg groups were higher significantly than the control (p < .05). The lysozyme, alkaline phosphatase, acid phosphatase (ACP), total antioxidative capacity activities in serum of fish fed 12 g/kg CHMM were higher significantly than those in the control (p < .05), while the total superoxide dismutase (SOD), total antioxidative capacity, catalase, alkaline phosphatase (AKP) and ACP activities in hepatopancreas of fish in 12 g/kg group were all significantly higher than those in the control (p < .05). Regression analysis showed that the relationships between dietary CHMM levels and either FCR, SGR, erepsin, pepsin or lysozyme activities were best expressed by quadratic or cubic regression equations, and the optimal inclusion levels are 11.4, 10.7, 10.7, 8.4 and 10.5 g/kg for maximum FCR, SGR, erepsin, pepsin and lysozyme activities, respectively. Under the present experimental condition, the optimal supplementary level of CHMM in the diet of Japanese seabass is 8–12 g/kg.     

The effects of dietary inulin and Jerusalem artichoke (Helianthus tuberosus) tuber on the growth performance,haematological, blood chemical and immune parameters of Nile tilapia (Oreochromis niloticus) fingerlings

This study investigated the effects of dietary inulin or Jerusalem artichoke (JA) on the growth performance, haematological, blood chemical and immune parameters of Nile tilapia fingerlings. Five treatment diets were designed to incorporate inulin at 0 (basal diet), 2.5 and 5.0 g/kg and JA at 5.0 and 10.0 g/kg. Two basal diets including fish meal and formulated experimental feed were used for fry and fingerling growing periods, respectively. During the fry growing period, larvae were fed treatment diets for 4 weeks. There were no significant differences in growth performance or survival rate. Fingerlings were then nursed with the formulated experimental diets from weeks 5 to 12. Fingerlings fed on inulin at 5.0 g/kg or JA at either level had better growth performance and survival rate than that fed on the basal diets. There were no significant differences in body composition. Dietary prebiotic inulin and JA increased red blood cell number (p < .05). Among the five blood chemistry parameters examined, both inulin at 5.0 g kg and JA (5.0 and 10.0 g/kg) increased blood protein (p < .05). Dietary inulin at 5.0 g/kg and JA at 5.0 and 10.0 g/kg increased total immunoglobulin and lysozyme activity (p < .05). Both inulin and JA inclusion diets increased alternative complement activity (p < .05). Taken together, dietary inulin at 5 g/kg and JA at 5.0 and 10.0 g/kg had beneficial effects on the growth performance, survival rate and immune of Nile tilapia fingerlings.     

Effects of dietary fishmeal replacement with Spirulina platensis on the growth,feed utilization,digestion and physiological parameters in juvenile gibel carp (Carassis auratus gibelio var. CAS III)

A 60‐day growth experiment was conducted to investigate the effect of dietary replacement of fishmeal by Spirulina platensis on growth performance, digestion and physiological parameters in juvenile gibel carp (5.0 ± 1.0 g). Four diets were formulated to replace 0 (SP0), 50% (SP50), 75% (SP75) and 100% (SP100) of dietary fishmeal protein by S. platensis respectively. Other two diets based on SP100 were supplemented with 2% dicalcium phosphate (SP100 + P) or 0.28% coated lysine (SP100 + Lys). The results showed that no significant differences of specific growth rate (SGR), feed efficiency (FE), feeding rate (FR) and protein efficiency ratio (PER) were observed between SP0 group and the replacement groups (SP50, SP75 and SP100). FE and PER of fish‐fed SP100 + Lys diet were significantly higher than the fish‐fed SP100 diet (p < .05). Apparent digestibility coefficients (ADCs) of dry matter, protein, energy and phosphorus increased significantly with the increasing S. platensis inclusion. Meanwhile, fish from SP100 + P or SP100 + Lys group had higher ADCs of nutrients compared to the SP100 group (p < .05). Compared with SP0 diet, fish‐fed S. platensis diets had higher activities of plasma superoxide dismutase, hepatopancreas total antioxidant capacity, plasma alkaline phosphatase and plasma lysozyme, as well as the lower content of plasma malondialdehyde. The present results indicated that dietary fishmeal could be fully replaced by S. platensis without any negative effects on growth performance of gibel carp. Supplementation of lysine in the S. platensis replacement diet could further improve the feed utilization of gibel carp.     

Fishmeal levels can be successfully reduced in white shrimp (Litopenaeus vannamei) if supplemented with DL‐Methionine (DL‐Met) or DL‐Methionyl‐DL‐Methionine (Met‐Met)

The main objective of this study was to evaluate the effect of methionine supplementation when reducing fishmeal levels in diets for white shrimp (Litopenaeus vannamei). Tested diets consisted of a positive control with 260 g/kg fishmeal (D1), two negative controls with 100 g/kg fishmeal and no amino acid (AA) supplementation (D2) or supplemented with lysine but not methionine (D3), and four additional diets with 100g/kg fishmeal supplemented with increasing levels of DL‐Met (1.0, 2.0 or 3.0 g/kg) (D4, D5, D6) or Met‐Met (1.0 g/kg) (D7). Each diet was fed to four groups of 30 shrimp for 8 weeks at a daily rate of 70 g/kg body weight. Reduction in fishmeal from 260 g/kg down to 100 g/kg did not significantly affect survival rate, feed conversion ratio (FCR), protein efficiency ratio (PER) or protein retention efficiency (PR%) of white shrimp. However, growth performance (final body weight, FBW; weight gain, WG; specific growth rate, SGR) was reduced when dietary fishmeal level was reduced from 260 g/kg (D1) to 100 g/kg without methionine supplementation (D2). The growth performance (FBW, WG and SGR) of shrimp was significantly increased by supplementation of the 100 g/kg fishmeal diet with increasing levels of DL‐Met (p < .05). Same performance as positive control (D1) was achieved with diets containing 100 g/kg fishmeal and supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. The highest values of growth performance (FBW, WG and SGR) were found in shrimp fed D6 and D7 diets, which were significantly higher than those of shrimp fed D2 and D3 diets (p < .05) but without statistical differences with shrimp fed D1, D4 and D5 diets (p > .05). The highest values of whole‐body and muscle protein contents were found in shrimp fed D1 diet, which were significantly higher than those of shrimp fed all other diets (p < .05). The highest value of intestinal tract proteolytic enzyme activity was found in shrimp fed Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) and 3 g/kg DL‐Met‐supplemented diet (D6) (p < .05). The highest values of apparent digestibility coefficients (ADCs) of dry matter and crude protein were found in Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) (p < .05). Shrimp fed the D1 diet showed the highest value of total essential amino acid (EAA) and was significantly higher than shrimp fed D2–D3 (p < .05) but without significant difference with shrimp fed D4–D7 (p > .05). In conclusion, results showed that same performance can be achieved with diets containing 260 or 100 g/kg fishmeal supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. Moreover, supplementation of limiting methionine in low‐fishmeal diets seems to improve the digestive proteolytic activity, improving digestibility of dry matter and protein, and eventually to promote growth of juvenile white shrimp in fishmeal reduction diets.     

Growth performance,muscle and liver composition,blood traits,digestibility and gut bacteria of beluga (Huso huso) juvenile fed different levels of soybean meal and lactic acid

The objective of this study was to assess the effects of fishmeal (FM) replacement with 0, 350 or 700 g/kg soybean meal (SBM) in combination with the supplementation of lactic acid (LA; 0, 10 or 20 g/kg) in the diets of juvenile beluga sturgeon (Huso huso; 700 ± 30 g). Nine isonitrogenous (400 g/kg protein) and isoenergetic (18 MJ/kg) diets were fed to beluga ad libitum, three times a day, for 60 days. The results showed that replacing FM with SBM without LA significantly reduced fish growth; on the other hand, LA supplementation had positive effects on fish fed diets that FM was replaced by SBM (p < .05). Increasing SBM in the diet altered the fatty acid profiles of the fish, reducing long‐chain polyunsaturated fatty acids and the n‐3/n‐6 fatty acids. High amounts of SBM (700 g/kg) caused reductions in the haematocrit, glucose and cholesterol levels in the blood (p < .05). In addition, the digestibility of protein, fat, dry matter and phosphorus was reduced when replacing FM with SBM, however, adding LA to the diets increased fish performance (p < .05), and this improvement was sharper in 2% LA groups. The number of LA bacteria increased significantly with the dietary supplementation of LA (p < .05). Based on these results, replacing 350 g/kg of FM with SBM and adding 20 g/kg LA to their feed do not negatively affect the biological and physiological indices of beluga.     

Soy protein concentrate as a substitute for fish meal in diets for juvenile Acanthopagrus schlegelii: effects on growth,phosphorus discharge and digestive enzyme activity

The current high demand and cost of fish meal (FM) necessities the evaluation of alternative plant protein ingredients in diets of farmed marine fish. A 56‐day feeding trial was performed to study the effects of replacement of FM with soy protein concentrate (SPC) in diets of Acanthopagrus schlegelii. Diets were prepared at levels of 0%, 30%, 47.5%, 65%, 82.5% and 100% SPC, respectively, replacing FM. The results indicated no significant differences (p > .05) in % weight gain (WG) and specific growth rate of fish fed S30% to S82.5% diets compared with the control diet while, further inclusion at 100% significantly depressed growth performance. SPC inclusion and phytase supplementation significantly affected the phosphorous discharge (P‐load) showing lowest value (3.83 ± 0.53 g/kg WG) in S100% compared to control (14.79 ± 0.37 g/kg WG) and in fish fed S30% diet (13.24 ± 0.89 g/kg WG) (p < .05). The results of this study showed that FM could be substituted up to 82.5% by SPC in the diet of Acanthopagrus schlegelii fingerlings (5.53 ± 0.12 g) without any adverse effects. Phytase supplementation SPC based diets could be effective in reducing the phosphorus load in the aquatic culture environment.     

Growth,enzymatic glutathione peroxidase activity and biochemical status of juvenile barramundi (Lates calcarifer) fed dietary fermented lupin meal supplemented with organic selenium

To investigate the effects of high level of lupin meal (LM) supplemented with organic selenium (OS) on the growth and blood biochemistry of barramundi (Lates calcarifer), four isocaloric and isonitrogenous diets were prepared, containing either non‐fermented or fermented LM, and either supplemented with 2 mg OS/kg (LM, LM_OS, FLM and FLM_OS), or not. A fishmeal (FM)‐based diet formulated for juvenile barramundi was used as a control diet. Fish (initial mean weight of 5.88 g) were triplicated and fed the test diets for 75 days. The findings demonstrated that growth performance of fish fed with the FLM and FLM_OS diets were similar to fish fed with the FM diet (p > .05). The antioxidant glutathione peroxidase (GPx) activity, and haemoglobin (Hb) of fish fed with the FLM_OS diet were significantly higher than that of FM‐fed fish (p < .05). Plasma alanine aminotransferase (ALT) activity was significantly increased in fish fed with non‐fermented diets (LM and LM_OS) than in those fed with fermented LM diets (FLM and FLM_OS) (p < .05). However, there were no significant differences in ALT activity among LM_OS, FLM, FLM_OS and FM diets. There was an interaction between the LM and OS on plasma CK activity; the CK of fish fed with diets supplemented with OS was higher in non‐fermented LM diets but lower in fermented LM diets (p < .05). This study suggests that fermented LM have an obvious potential to substantially replace 75% FM protein in the diets of barramundi.     

Effects of totally replacing dietary fish oil by linseed oil or soybean oil on juvenile hybrid sturgeon,Acipenser baeri Brandt♀×A. schrenckii Brandt♂

The growth performance, body composition, fillet fatty acid content, serum hepatic enzymes and postprandial changes in serum lipid metabolism of hybrid sturgeon (70.8 ± 0.5 g) were investigated to determine the effects of total replacement of 80 g kg^‐1 fish oil (diet A) with linseed oil (diet B) and soybean oil (diet C), respectively. No significant differences in weight gain rate and specific growth ratio were observed among all fish groups (p > .05). Diet A fish group had the highest, but diet B fish group had the lowest feed intake (p < .05). Feed efficiency of fish fed diet A was significantly lower than the other two fish groups (p < .05). Fish fed diet A had the lowest fillet and liver lipid contents (p < .05). Serum lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase activities of fish fed diet A were significantly lower than those of fish fed diets B and C (p < .05). The contents of linoleic acid (C18:2n6) and linolenic acid (C18:3n3) in fillets showed a significantly positive linear correlation with the diets. Serum glucose and non‐esterified fatty acid were just affected by the time point (p < .05). The lipid source, time point and interaction of both factors had significant effects on serum triglyceride, high‐density lipoprotein cholesterol and low‐density lipoprotein cholesterol (p < .05). Serum total cholesterol was only affected by interaction of time point and lipid source (p < .05), and ketone body was not affected by lipid source, time point or interaction of both factors (p > .05). In summary, total replacement of fish oil with linseed oil or soybean oil had no significant adverse effects on hybrid sturgeon growth during 84‐day period, and linoleic acid and linolenic acid in fillet were modified by dietary treatments.     

Effects of dietary inulin and Jerusalem artichoke (Helianthus tuberosus) on intestinal microbiota community and morphology of Nile tilapia (Oreochromis niloticus) fingerlings

This study investigated the effects of dietary inulin and Jerusalem artichoke (JA) on intestinal microbiota and morphometry of Nile tilapia fingerlings. Five treatment diets were designed to supplement inulin at 0 (basal diet), 2.5 and 5.0 g/kg, and JA at 5.0 and 10.0 g/kg. Nile tilapia larvae were fed experimental diets from the first feeding through the fingerling stage (84 days). The cultivation‐dependent technique showed that dietary inulin at 5.0 g/kg and JA (at both levels) increased lactic acid bacteria and Bifidobacterium spp., but decreased Vibrio spp. (p < .05). PCR‐DGGE targeting 16S ribosomal RNA gene revealed that dietary inulin and JA generated different profiles of microbial community compared with fish fed a basal diet. Compared with fish fed the basal diet, a greater intestinal villi height was observed in fish fed 5.0 g/kg inulin and JA at both levels (p < .05). A larger relative goblet cell number were observed in the anterior intestine of fish fed 5.0 g/kg inulin or JA (p < .05). Overall, dietary inulin (5.0 g/kg) and JA (5 and 10.0 g/kg) since the first feeding had effects on modulating the intestinal microbiota and morphology of Nile tilapia fingerlings.     

Dietary taurine impacts the growth,amino acid profile and resistance against heat stress of tiger puffer (Takifugu rubripes)

A 56‐day feeding trail was conducted to evaluate the effects of taurine (Tau) supplementation on growth performance, amino acid profile and heat stress resistance capacity in juvenile Takifugu rubripes (initial body weight: 32.28 ± 0.20 g). Tiger puffer were distributed into five groups and each received one of the following diets: each diet was supplemented with 0 (T1), 5 (T2), 10 (T3), 20 (T4) or 50 (T5) g Tau/kg, respectively. Growth performances were significantly ameliorated with fed diet T3 (p < .05). The Tau content of muscle increased significantly as dietary Tau increased (p < .05). Compared to the control group, fish fed diets T4 and T5 showed significantly higher concentration of triglyceride and urea, respectively (p < .05), while taurine transporter (TauT) gene and IGF‐1 gene expression increased significantly in fish fed diets T3 and T4, respectively (p < .05). After acute heat stress, HSP70 gene expression levels were significantly greater in the livers and spleens of T. rubripes (p < .05) fed diet supplemented with Tau. Levels of complement C4 were highest in fish fed 10 g/kg Tau (p < .05). These data suggested that dietary supplemented with taurine indicated positive effects on growth performances, amino acid profile and resistance against heat stress for T. rubripes.     

Dietary manganese requirement of juvenile hybrid grouper,Epinephelus lanceolatus × E. fuscoguttatus

An 8‐week feeding trial was conducted to estimate the optimum dietary manganese (Mn) requirement for juvenile hybrid grouper, Epinephelus lanceolatus × E. fuscoguttatus. The basal diet was formulated to contain 520 g/kg crude protein from casein and fishmeal. Manganese methionine was added to the basal diet at 0 (control group), 2.5, 5, 10, 20 and 40 mg Mn/kg diet providing 7.48, 10.34, 13.76, 19.72, 31.00 and 53.91 mg Mn/kg diet, respectively. Each diet was randomly fed to triplicate groups of juveniles, and each tank was stocked with 20 fish (initial weight, 60.06 ± 0.68 g). The manganese content in rearing water was monitored and kept below 0.01 mg/L. Results showed that the weight gain ratio (WGR), protein efficiency ratio (PER), specific growth rate (SGR), Mn contents in whole body, liver and vertebra, and activities of hepatic Mn superoxide dismutase (Mn‐SOD), total SOD (T‐SOD) and glutathione peroxidase (GSH‐PX) were significantly improved by dietary Mn supplementation (p < .05). However, dietary Mn did not affect arginase (DArg) activity. The highest feed conversion ratio (FCR) was observed in fish fed the basal diet (p < .05). No significant differences were found on the Cu and Zn contents in whole body by supplementing dietary Mn. Supplemented Mn in diets had significantly effect on liver and vertebral trace element deposition (p < .05). Fish fed the basal diet had the highest Fe and Zn contents in vertebra (p < .05). There were no significant differences on hepatic pyruvate decarboxylase (PDC) activity with supplemented Mn levels below 13.76 mg/kg. As biomarker of oxidative stress, malondialdehyde (MDA) content in liver was significantly higher in fish fed the basal diet (p < .05). Using the broken‐line models based on SGR, dietary Mn requirement of the juvenile hybrid grouper was estimated to be 12.70 mg/kg diet.