Effects of replacing fish meal with corn gluten meal on growth,feed utilization,nitrogen and phosphorus excretion and IGF‐I gene expression of juvenile Pseudobagrus ussuriensis

Seven isonitrogenous and isolipidic diets containing fish meal (FM) protein replaced by corn gluten meal (CGM) protein at 0% (the control, C0), 10% (C10), 20% (C20), 30% (C30), 40% (C40), 50% (C50) and 60% (C60) were fed to juvenile Pseudobagrus ussuriensis for 8‐weeks to evaluate the effects of FM protein replaced by CGM protein on growth, feed utilization, nitrogen (N) and phosphorus (P) excretion and IGF‐I gene expression of juvenile P. ussuriensis. The results showed that the replacement level up to 40% did not affect the weight gain, specific growth rate (SGR), feed intake and protein efficiency ratio, whereas these parameters were depressed by further replacement level. Apparent digestibility coefficients (ADC) of dry matter, crude protein significantly decreased, but ADC of phosphorus significantly increased with increasing dietary CGM levels (p < .05). Fish fed diets with FM protein replaced by CGM protein led to an increase in nitrogen excretion, but led to a reduction in phosphorus excretion. No significant differences were observed in alpha‐amylase and lipase activities of intestine (p > .05). The lowest pepsin activity was found in C60 group. Fish fed diet C40, C50 and C60 had significantly lower serum lysozyme activity compared with fish fed diet C0 (p < .05). The lowest plasma alkaline phosphatase activity and the highest plasma alanine aminotransferase and aspartate aminotransferase activities were observed in C60 group. Fish fed diet C60 had significantly lower hepatic IGF‐I gene expression compared with fish fed diet C10 (p < .05). Broken‐line model analysis based on SGR against the CGM substitution level indicated that the appropriate replacement level was 37.7%.     

Effects of complete fish meal replacement by rice protein concentrate with or without lysine supplement on growth performance,muscle development and flesh quality of blunt snout bream (Megalobrama amblycephala)

An 8‐week feeding trial was conducted to evaluate the effects of fish meal (FM) replacement by rice protein concentrate (RPC) with supplementation of microcapsule lysine (ML) or crystalline lysine (CL) on growth performance, muscle development and flesh quality of blunt snout bream. Four isonitrogenous and isoenergetic diets were formulated, including FM diet (containing 50 g/kg FM), RPC diet (FM replaced by RPC), MRPC diet (FM replaced by RPC with ML supplementation) and CRPC diet (FM replaced by RPC with CL supplementation). Fish fed FM diet had significantly higher weight gain, feed efficiency, protein efficiency ratio and nitrogen and energy utilization than that of RPC group, but showed no statistical difference with other treatments. In addition, fish fed RPC diet showed higher muscle fibre frequency in the 20‐ to 50‐μm class but lower >50‐μm class and higher cooking loss than that of the other groups. Furthermore, no significant difference was found in whole‐body proximate compositions, frequency distribution of <20‐μm‐diameter fibres, texture, muscle content, collagen, pH 24 hr post‐mortem and sensory quality. The results showed that RPC supplemented with ML or CL could replace fishmeal without any adverse effects on growth performance and flesh quality for blunt snout bream.     

Evaluation of pea proteins and poultry protein as fish meal alternatives in the diets for juvenile black sea bream,Acanthopagrus schlegelii

The potential of three different protein resources (pea protein isolate, PPI; pea protein concentrate, PPC; enzyme treated poultry protein, ETPP) as fish meal (FM) alternative protein in diets for juvenile black sea bream, Acanthopagrus schlegelii. (initial average weight 7.90 ± 0.13 g) was evaluated. Seven isonitrogenous and isoenergetic diets were formulated to replace FM at 0% (T0, control diet), 8% (designated as T1‐T3) and 16% (designated as T4‐T6) using PPI, PPC and ETPP respectively. Each diet was randomly assigned to triplicate groups of 25 juvenile fish for 8 weeks. At the end of the feeding period, survival rate was not significantly affected by dietary treatments. Growth performance in T6 (16% ETPP) group was significantly inferior to T0 group, however, weight gain and specific growth rate in other treatments showed no significant differences (P > 0.05). Mean feed intake, feed efficiency ratio and protein efficiency ratio were also poorer in fish fed in T6 than those of fish fed with the control diet respectively. Apparent digestibility coefficients (ADCs) of dry matter and crude protein for fish fed ETPP diets were significant lower than those of fish fed with the control diet, whereas ADCs of lipid were unaffected by dietary treatments. ADC's of dietary Leu, Ile, His and Lys was also significantly influenced. There were no marked variations in proximate compositions of dorsal muscle. With regard to plasma characteristics, significant difference was observed in triacylglycerol content. Ammonia concentration in plasma tended to increase in alternative protein diets as substitution level increased. There were significant differences in aspartate aminotransferase activities among groups, but alanine aminotransferase levels were unaffected by treatments. In conclusion, the present study demonstrated that PPI and PPC were potential protein sources for using in juvenile black sea bream diet. However, the substitution level of FM by ETPP should be limited within 16%.     

Evaluation of feed utilization and growth performance of juvenile striped catfish Pangasianodon hypophthalmus fed diets with varying inclusion levels of corn gluten meal

A nutrition trial with striped catfish (Pangasianodon hypophthalmus) juveniles was undertaken to evaluate the effect of replacing dietary fishmeal (FM) protein with corn gluten meal (CGM). A diet with FM as the main protein source was used as the control diet (FM). Five experimental diets (approximately 320 g kg^?1 crude protein) were formulated to progressively replace 20% (CGM20), 40% (CGM40), 60% (CGM60), 80% (CGM80) and 100% (CGM100) of FM protein. Fifteen fish per tank (initial weight 11.2 ± 0.6 g) were randomly distributed into 18 80‐litre fibreglass tanks connected to a closed recirculation system (temperature 30.3 ± 1.0 °C). The diets were tested in triplicate for 12 weeks. The final weight and specific growth rate (SGR) of fish fed diets CGM20, CGM40 and CGM60 were not significantly different compared to fish fed the FM diet. Feed intake (FI) tended to decrease with increasing dietary CGM level. Striped catfish fed FM, CGM20 and CGM40 had significantly lower feed conversion ratio (FCR) compared with fish fed CGM80 and CGM100 (P < 0.05). The protein efficiency ratio (PER) of fish fed the CGM80 and CGM100 diets was significantly lower than those of all other treatments (P < 0.05). Total ammonia‐nitrogen (TAN) excretion increased with elevated dietary CGM inclusion. The viscerosomatic index (VSI) of fish fed the CGM80 and CGM100 diets were significantly higher (P < 0.05) than those of fish fed the other treatments. The crude lipid content in the final body composition of the striped catfish was elevated significantly with increasing dietary CGM levels. Fish fed the CGM80 and CGM100 diets displayed haematocrit levels significantly lower (P < 0.05) than those fed the other diets. The haemoglobin content in fish was significantly higher in fish fed CGM20 and lower at CGM100 compared to fish fed the FM diet. The results of the present trial indicated that the optimum level of FM protein replacement with CGM determined by quadratic regression analysis was 25.1% on the basis of maximum SGR.     

Partial Replacement of Fish Meal by Fermented Soybean Meal in Diets for Black Sea Bream,Acanthopagrus schlegelii,Juveniles

The effect of fish meal (FM) substitution with fermented soybean meal (FSBM) in the diets of the carnivorous marine fish, black sea bream, Acanthopagrus schlegelii, was investigated. An 8‐wk feeding trial was conducted with black sea bream (11.82 ± 0.32 g; mean initial weight) in indoor flow‐through fiberglass tanks (25 fish per tank). Six isonitrogenous and isoenergetic diets were formulated, in which FM was replaced by FSBM at 0% (control diet), 10% (FSBM10), 20% (FSBM20), 30% (FSBM30), 40% (FSBM40), or 50% (FSBM50), respectively. Each diet was fed to triplicate groups of fish twice daily to apparent satiation. The results showed that there was no difference in survival of black sea bream during the feeding trial. Fish fed the FSBM10 or FSBM20 diet showed comparable growth performance compared with fish fed the control diet (P > 0.05), whereas more than 30% replacement of FM adversely affected weight gain and specific growth rate (P < 0.05). Feed intake was significantly lower for fish fed the FSBM50 diet compared with fish fed the control diet. Feed conversion ratio (FCR) tended to increase with increasing dietary FSBM with the poorest FCR observed for fish fed the FSBM50 diet. Protein efficiency ratio and protein productive values showed similar patterns. Apparent digestibility of nutrients significantly decreased with increasing dietary FSBM level. With the exception of protein content, no significant differences in whole body and dorsal muscle composition were observed in fish fed the various diets. Fish fed the FSBM50 diet had significantly lower intraperitoneal ratio than fish fed the control or FSBM10 diet. Hepatosomatic index and condition factor were unaffected by dietary treatments. This study showed that up to 20% of dietary FM protein could be replaced by FSBM protein in the diets of juvenile black sea bream.     

Effects of natural feeding stimulants and glutamic acid supplementation on the feed intake,growth performance and digestive enzyme activities of red sea bream (Pagrus major) fed fish meal‐free soy protein concentrate (SPC)‐based diet

Two experiments were conducted for red sea bream (Pagrus major). In experiment 1, the optimum level of glutamic acid and natural feeding stimulants to enhance feed intake were determined and found that glutamic acid level of 0.5% and fish meat hydrolysate (FMH) were effective. In experiment 2, fish were fed with soy protein concentrate (SPC)‐based diet with synthetic feeding stimulants (Basal diet), the Basal diet with FMH (FMH diet), the FMH diet with glutamic acid (FMHG diet) and with fish meal diet (FM diet) as a control until satiation for 8 weeks. Feed intake of FMHG‐fed fish was significantly higher than others (p < 0.05). Specific growth rate and the feed conversion ratio of FMHG were comparable to those of FM‐fed fish (p > 0.05). Relative visceral fat ratio and crude lipid content of any SPC‐based diet‐fed fish tended to be lower than those of FM diet‐fed fish. There were no significant differences in trypsin and lipase activities hepatopancreas among treatments. SPC can be utilized as a sole protein source in a diet for red sea bream. The lower growth performance in SPC‐based diet‐ fed fish was not due to poor digestive enzyme secretion but could be associated with lipid utilization disorder.     

Utilization of combined extruded soybean and corn gluten meals as feed ingredients for juvenile rainbow trout,Oncorhynchus mykiss diet

In this study, feeding experiment and subsequent digestibility trial were performed to investigate the utilization of extruded soybean meal (SBM) and corn gluten meal (CGM) as feed ingredients for juvenile rainbow trout. Plant ingredients have undergone extrusion at low temperature (100°C, LT) or high temperature (150°C, HT) for 30 s. Four isonitrogenous (44%, crude protein) and isolipidic (14%, crude lipid) diets were formulated. Control diet is fishmeal based while a combined (1:1) non‐extruded SBM and CGM for NE diet, LT SBM and LT CGM for LT diet and HT SBM and HT CGM for HT diet. Two hundred forty rainbow trout juveniles (7.8 g average body weight) were randomly divided into 12 rectangular 60 L glass aquaria and offered four different diets in triplicate. Fish were fed at satiation twice a day, six days a week for 12 weeks. Phosphorus in phytic acid level of extruded ingredients decreased through extrusion cooking. Final weight, weight gain, SGR and PER of fish fed HT diet were significantly (p < .05) higher than those fed with NE diet. Apparent digestibility coefficient for protein of LT and HT diets is significantly higher than of NE diet. The results of this study demonstrated that HT extruded SBM and CGM are suitable feed ingredients for rainbow trout diet without compromising fish growth, feed utilization and fish body composition.     

Effects of fish meal replacement by low‐gossypol cottonseed meal on growth performance,digestive enzyme activity,intestine histology and inflammatory gene expression of silver sillago (Sillago sihama Forsskál) (1775)

A 56‐day feeding trial was conducted to evaluate the effects on the growth performance, digestive enzyme activity, inflammatory genes expression and intestine histology of silver sillago, Sillago sihama (Forsskål 1775), by replacing fish meal (FM) with low‐gossypol cottonseed meal (LCSM). Five isonitrogenous and isolipidic diets were formulated, including R0 group (control, containing 550.0 g/kg FM), R16 group (88.5 g/kg LCSM and 461.5 g/kg FM), R32 group (177.0 g/kg LCSM and 373.0 g/kg FM), R48 group (265.5 g/kg LCSM and 284.5 g/kg FM) and R64 group (354.0 g/kg LCSM and 196.0 g/kg FM). Fish fed R0 and R16 groups had a significantly higher weight gain rate (WGR) and specific growth rate (SGR) than R48 and R64 groups (p < .05). In contrast to whole‐body crude protein, whole‐body moisture increased with the FM level of substitution (p < .05). With the increased amount of LCSM in the diet, the activity of intestinal amylase (AMS) increased significantly (p < .05), and intestinal trypsin (TRP) decreased (p < .05). Dietary LCSM substitution upregulated the expression of intestinal tumour necrosis factor‐α (TNF‐α), the nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB), and interleukin one beta (IL‐1β), but downregulated tight junction proteins ZO‐1(ZO‐1), transforming growth factor beta‐3 (TGF‐β3) and interleukin 10 (IL‐10) expression. Histological analysis revealed progressive morphological damage to the mid‐intestine with higher levels of FM replacement. These results showed that 88.5 g/kg (16%) of FM replaced by LCSM with amino acids (methionine and lysine) supplementation did not significantly reduce growth compared with FM‐based control.     

Effect of tributyrin supplementation in high‐soya bean meal diet on growth performance,body composition,intestine morphology and microbiota of juvenile yellow drum (Nibea albiflora)

Six equal‐protein and equal‐lipid diets were formulated: the fish meal (FM) diet, the soya bean meal (SBM) diet with 40% of FM protein replaced by SBM protein and tributyrin (TB) diets with 0.05% (TB0.05), 0.10% (TB0.1), 0.20% (TB0.2) and 0.40% (TB0.4) tributyrin supplemented in the SBM‐based diet. Each kind of diet was randomly fed to triplicate tanks with 20 fish per tank. Fish were fed apparent satiation twice daily for 56 days. No significant difference in weight gain rate (WGR) and feed efficiency rate (FER) was observed between fish fed the FM, TB0.1 and TB0.2 diets (p > .05). Muscle histidine and arginine proportion of fish fed TB0.1 diet was significantly higher than that of fish fed the SBM diet (p < .05). Intestine morphology results indicated that the supplementation of 0.1% tributyrin significantly improved the mucosal fold height, microvilli length and microvilli density when compared with those of fish fed the SBM diet (p < .05). The supplementation of dietary tributyrin suppressed the pro‐inflammatory gene expression, which may be due to the improvement of physical barrier and modification of microbial communities, such as Acinetobacter, Rhodocyclaceae, Brevundimonas, Sphingopyxis, Hydrogenophaga, Methyloversatilis and Devosia. In conclusion, dietary 0.1% tributyrin supplementation in high‐soya bean meal diet improved growth performance, flesh quality and intestinal morphology structure integrity of yellow drum.     

Partial replacement of fishmeal with Clostridium autoethanogenum single‐cell protein in the diet for juvenile black sea bream (Acanthopagrus schlegelii)

Clostridium autoethanogenum protein (CAP) is a single‐cell protein derived from ethanol production and may have potential to become a substitute for fishmeal in aquafeeds. A 70‐day feeding trial was conducted with black sea bream (Acanthopagrus schlegelii) (mean initial weight 6.03 ± 0.09 g) to evaluate partial replacement of fishmeal with CAP in diets. Seven isonitrogenous and isoenergetic diets were formulated with graded levels of CAP (0, 4.85, 9.70, 14.55, 19.40, 38.80 and 58.20%) to replace fishmeal. The inclusion of CAP at all dietary levels tested did not significantly affect the growth performance (p > .05). Fish fed the CAP58.20% diet showed a significantly lower feeding rate, with significantly higher protein efficiency ratio and feed efficiency ratio compared with fish fed the other diets (p < .05). No statistical differences were found in dorsal muscle and whole‐body compositions. Total superoxide dismutase in serum of fish fed CAP58.20% diet was significantly lower compared with that of the control. Malondialdehyde, catalase, total antioxidant capacity and digestive enzyme activities revealed no significant differences among dietary treatments. Phosphorus retention efficiency significantly increased, and phosphorus discharge showed a downward trend with increasing CAP inclusion levels. In conclusion, the results indicated that CAP is a safe and effective alternative protein source, which can replace fishmeal in the diet of black sea bream up to 58.20%, without adverse effects on growth performance, antioxidation and digestive enzyme activity. This study has shown the potential of converting industrial waste into a high protein feed ingredient for aquafeeds.     

Dietary supplementation of lysine and/or methionine on performance, nitrogen retention and excretion in pacu Piaractus mesopotamicus reared in cages

A study was conducted to evaluate the effect of dietary supplementation of lysine and/or methionine on growth performance, nitrogen retention and excretion in pacu juveniles reared in cages. Five diets were prepared; four diets based on plant ingredients containing 23% digestible protein (DP), basal: Lys- and Met-deficient, 23L: basal supplemented with lysine only, 23M: basal supplemented with methionine only, and 23LM: basal supplemented with both amino acids and a protein-bound AAs diet based on fish and soybean meal, containing 30% DP. Survival, specific growth rate, protein efficiency rate and feeding cost were not influenced by the dietary treatments (P > 0.05). Fish fed basal diet showed the lowest mean of N retention. Fish fed 30DP diet showed the best results of weight gain (WG) and apparent food conversion rate (FCR) among the dietary treatments. On the other hand, WG in the 23LM group and FCR in the 23LM and 23M groups were not significantly different from the group fed 30DP diet, and showed the highest mean of N retention. There was higher N excretion (P < 0.05) when the fish were fed 30DP and 23L diets than the other dietary treatments. Fish fed plant protein-based diets containing 23% DP supplemented with both amino acids or methionine alone showed satisfactory growth and N retention results when compared with fish fed 30DP diet, with the advantage of lower N emissions into water. The results also evidence the pacu's great potential to be reared in cages.     

Using stable isotope analysis to assess the relationship among dietary protein sources,growth, nutrient turnover and incorporation in Nile tilapia (Oreochromis niloticus)

Nile tilapia (1.20 g) were fed for 56 days in five treatments (FM100 containing only fish meal [FM] as a protein source; soybean meal (SBM) replace 25%, 50%, 75% and 100% of FM protein in the diets of FM75, FM50, FM25 and FM0, respectively) to assess the effects of dietary protein sources on growth, turnover half‐life of nitrogen and carbon stable isotopes (δ¹³C and δ¹⁵N) in muscle, isotope discrimination factors (Δ¹⁵N and Δ¹³C), and the relative contribution of protein sources to muscle growth. Results showed that the final body weight, weight gain and specific growth rate of fish fed diet FM25 were significantly higher than other treatments (p < .05). By day 35, fish under all treatments reached isotopic equilibrium, and the equilibrium values consistently increase as a function of stable isotope values in diets. Growth accounted for most isotopic changes in muscle and resulted in significantly shorter half‐lives of nitrogen and carbon in FM25 (p < .05). The Δ¹⁵N of FM25 and Δ¹³C of FM0 were significantly lower than other treatments (p < .05). The proportional contributions of SBM protein were significantly higher than their respective levels in FM75 and FM25 (p < .05), indicating a preferential incorporation of nitrogen from the SBM in muscle tissue.     

Effects of feeding a fish meal‐free soy protein concentrate‐based diet on the growth performance and nutrient utilization of red sea bream (Pagrus major)

Two groups of red sea bream (average body weight 85 g) were fed to satiation fish meal (FM) or FM‐free soy protein concentrate (SPC)‐based diet (FM‐sat and SPC groups respectively). A third group (FM‐pair) was fed the same amount of FM as of SPC fed to SPC‐sat group for 6 weeks. Growth rate of SPC group was significantly slower than of FM‐sat and FM‐pair groups (p < 0.05). Feed conversion ratios of FM‐sat and FM‐pair groups were similar and were better than that of SPC group (p < 0.05). Visceral fat somatic index of SPC group was significantly lower than of the other groups (p < 0.05), while that of the latter two groups were similar. Plasma triglyceride of FM‐sat and FM‐pair groups was similar and lower than the level of SPC group (p < 0.05). Trypsin activity in hepatopancreas of SPC group was significantly lower than that of other groups (p < 0.05). We suggest a low growth of SPC group was not simply related to low‐feed intake. Feeding of a FM‐free SPC‐based diet may reduce lipid accumulation and consequently lead to low‐growth performance, in red sea bream.     

Utilization of corn gluten meal as a protein source in the diet of white shrimp Litopenaeus vannamei

A 57‐day feeding trial was designed to assess the potential of corn gluten meal (CGM) as a plant protein source in practical feeds for white shrimp Litopenaeus vannamei. Five experimental diets providing 350 g kg^?1 protein and 110 g kg^?1 lipid were prepared, where 0%, 25%, 50%, 75% and 100% of fishmeal (FM) protein was substituted by protein from CGM. The results showed that partial or complete replacement of FM with CGM did not affect survival. The growth of the shrimp declined as the levels of CGM increased, diets containing CGM showing a significantly lower final weight (3.2–5.9 g) and specific growth rates (1.7–2.7% per day) compared to those fed on the diet with 0 CGM (7.1 g and 3.0% per day). Feed conversion ratio was also significantly affected by CGM level. The inclusion of CGM resulted in a statistical decrease in the apparent digestibility (AD) of dry matter from 77.9% to 66.0% and in AD of protein from 80.5% to 52.0%, of feed. The AD of amino acids, with the exception of lysine, declined with the dietary incorporation of CGM. In summary, reduced palatability, low protein digestibility and a deficiency of lysine and methionine seem to be the major reasons behind a depressed growth in shrimp fed on CGM protein‐based diets.     

Growth performance and feed utilization of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) and tilapia galilae Sarotherodon galilaeus (Linnaeus, 1758) fingerlings fed plant protein-based diets

This study was designed to determine the effect of complete substitution of fish meal (FM) by three plant protein sources including extruded soybean meal (SBM), extruded full‐fat soybean (FFSB) and corn gluten meal (CGM) on growth and feed utilization of Nile tilapia Oreochromis niloticus and tilapia galilae Sarothrodon galilaeus. Four isonitrogenous of crude protein (ca. 28.0%) and isocaloric (ca. 19 MJ kg⁻¹) experimental diets were formulated. The control diet (diet 1) was prepared with FM as the main protein sources. Diets 2–4, each FM control diet, were completely substituted with SBM (diet 2), FFSB (diet 3) and CGM (diet 4). l ‐lysine and dl ‐methionine were added to plant protein diets to cover the nutritional requirements of tilapia. Each treatment was allocated to three net pens and fed for 17 weeks. Nile tilapia fed the control diet showed significantly higher (P≤0.05) values for final body weight (FBW), feed intake (FI), weight gain (WG) and specific growth rate (SGR), whereas fish fed the diet with CGM achieved the lowest values. Tilapia galilae fed SBM diet recorded the highest (P≤0.05) values for growth performance. Better feed conversion ratio (FCR) for both Oreochromis niloticus and Sarothrodon galilaeus was observed when fish were fed SBM diet, whereas the worse FCR was recorded for FFSB diet. Feed utilization parameters including protein productive value (PPV), fat retention (FR) and energy retention (ER) showed significant differences (P≤0.05) for both the species fed different dietary protein sources. The present results suggest that, for Nile tilapia, both SBM and FFSB supplemented with dl ‐methionine and l ‐lysine can completely replace dietary FM. Meanwhile, S. galilaeus fed SBM diet exhibited comparable growth and feed utilization with those fish fed a fish‐meal‐based diet.     

Complete replacement of fish meal by plant protein ingredients with dietary essential amino acids supplementation for juvenile blunt snout bream (Megalobrama amblycephala)

Six extruded diets were formulated with a graded level of fish meal (FM); diet 1 and diet 2 were formulated with 80 g/kg FM; diet 3 and diet 4 were formulated with 40 g/kg FM; and diet 5 and diet 6 were devoid of FM. Hence, diet 2, diet 4 and diet 6 were supplemented with essential amino acids (EAAs). The diets were fed throughout an eight‐week feeding trial. The results revealed that specific growth rate (SGR), feed conversion ratio (FCR), body weight gain (BWG) and protein efficiency ratio (PER) were influenced by FM reduction and improved by the addition of EAA (p < 0.05). A survival rate (SR), whole body content of protein, lipid, moisture and ash, and plasma total protein (TP), albumin (ALB), triglyceride (TG) and urea (UN) did not influence by dietary treatments (p > 0.05). Additionally, target of rapamycin (TOR) pathway did not influence by dietary treatments (p > 0.05). Expression levels of hepatic peptide transporter 1 (Pept1) and peptide transporter 2 (Pept2) decreased against FM reduction and improved significantly in the groups fed diet 4 and diet 6. In summary, the findings revealed that diet containing plant proteins mixture supplemented with EAA could totally replace FM in the practical diet of blunt snout bream.     

Effects of dietary sodium butyrate on growth,diet conversion,body chemical compositions and distal intestinal health in yellow drum (Nibea albiflora,Richardson)

The present study was conducted to investigate the effects of sodium butyrate (SB) on the physical barrier function, pro‐inflammatory response and possible underlying mechanisms in the distal intestine (DI) of yellow drum when fed a high‐SBM diet. Three iso‐proteic and iso‐lipidic diets were formulated with fish meal (FM, the control), 45% fish meal protein replaced by SBM (SBM) and 45% fish meal protein replaced by SBM but supplemented with 0.15% SB (SBM + SB). Fish were fed twice daily for 10 weeks. Results indicated that SB supplementation significantly increased the specific growth rate (SGR) and feed efficiency ratio (FER) and methionine content of muscle when compared with those of fish fed the SBM diet (p < .05). The morphologic histology results showed that SB dramatically improved the physical barrier structure, characterized as increases of fold height (FH) and muscular thickness (MT) (p < .05). RT‐qPCR data were accordant with morphologic histology results, in which claudin 3, claudin 4 and occludin were increased while claudin 7 and myosin light chain kinase (MLCK) mRNA expression levels were decreased (p < .05). Sodium butyrate also exerted anti‐inflammatory function, which may be attributed to the suppression of nucleus p65 protein expression. Results suggest SB can be incorporated in high‐SBM diets to ameliorate the negative consequences of alternative dietary ingredients on yellow drum physiology.     

Effect of dietary replacement of fish meal by soybean protein concentrate on growth performance and phosphorus discharging of juvenile black sea bream,Acanthopagrus schlegelii

The 8‐week experiment was conducted to evaluate the effects of partial replacement of fish meal (FM) with soybean protein concentrate (SPC) on juvenile black sea bream, Acanthopagrus schlegelii (10.70 ± 0.04 g). Diets were formulated to replace FM protein by SPC at 0, 8, 16, 24, 32 or 40% (designated as T1, T2, T3, T4, T5 and T6, respectively). Diets except T1 were supplemented with phytase at 2000 phytase activity U kg^?1. The results showed that survival rate, growth performance and feed utilization were not significantly affected by increasing dietary SPC. Fish fed diet T3 had higher feed intake compared to those fed T1, T2 and T5 diets. Whole body compositions of black sea bream were significantly influenced by SPC replacing FM except for protein, ash and phosphorus content. Condition factor of fish was significantly lower in T2 than that of fish in T3 group. Apparent digestibility coefficients (ADCs) of dry matter was higher in fish fed T6 diet than those of fish fed T1 and T2 diets, ADCs of phosphorus increased with dietary SPC level up to T3 and then decreased. The results obtained in this study indicate that FM protein could be effectively replaced by SPC protein with phytase in diet of black sea bream.     

Effects of replacing fish meal with soya protein concentrate on growth,feed efficiency and digestibility in diets for snakehead,Channa striata

Soya bean meal‐based formulated feeds have recently become available for snakehead culture in Vietnam. This study was conducted to determine the appropriate replacement of fish meal (FM) protein by another soya product, soya protein concentrate (SPC), in snakehead (Channa striata) diets. Five iso‐nitrogenous (45% crude protein) and iso‐caloric (19 KJ g^?1) practical diets were formulated to replace 0% (control), 40%, 60%, 80% and 100% of protein FM by protein SPC (100% FM, 40% SPC, 60% SPC, 80% SPC and 100% SPC respectively). A digestibility experiment was also conducted with the same formulated diets with addition of 1% chromic oxide. Fish fed 100% FM and 40% SPC diets had significantly better growth and survival compared with other treatments. Feed intake, feed conversion ratio, protein efficiency ratio and net protein utilization, trypsin and chymotrypsin activities of experimental fish fed 100% FM and 40% SPC diets were significantly higher than those fed other diets. The apparent digestibility coefficient (ADC) of the diet and diet components, ADC_diet, ADC_protein and ADC_lipid, of fish fed diet 40% SPC and 100% FM treatment were significantly higher than those of other treatments. The cost/kg fish produced in diets 100% FM and 40% SPC was much lower compared with other treatments. Dietary inclusion levels of SPC in diet above 40% significantly affected fish survival, growth, digestibility and trypsin and chymotrypsin activities, although fish chemical composition was not greatly affected.