A 9-week feeding trial was conducted to evaluate the optimum dietary level of PROTIDE (PRO), a single-cell protein obtained from the bacteria Corynebacterium ammoniagenes, as a substitute for fish meal in the diet of whiteleg shrimp Litopenaeus vannamei. Five diets were formulated that replaced fish meal at 0% (PRO0), 10% (PRO2), 20% (PRO4), 30% (PRO6) and 40% (PRO8). Fifty shrimp averaging 0.15 ± 0.02 g (mean ± SD) body weight were randomly distributed between 20 experimental tanks and fed one of the five experimental diets. At the end of the experiment, final weight, weight gain, specific growth rate and feed conversion ratio of shrimp fed PRO0 and PRO2 diets were significantly improved compared to those fed PRO6 and PRO8 diets (P < 0.05). The proximate composition of muscle and the whole body indicated an increase in crude protein content with an increase in dietary PRO level. These results suggest that, for whiteleg shrimp, the optimum dietary level of PRO when used as a replacement for fish meal should be greater than 10% (PRO2) but less than 20% (PRO4) without any additional dietary amino acid supplementation.

Recent research is increasingly shedding light on the important role that microbial metabolites such as γ-aminobutyric acid (GABA) play in the context of nutrition, cognition, immune function, and the modulation of the gut microbiome. Yet, very few trials were conducted to assess the effects of its supplementation on biomarkers of fish health. Therefore, an eight-week feeding trial was devised to evaluate GABA supplementation in juvenile olive flounder, (Paralichthys olivaceus). A total of 630 fish with an average weight of 4.90 ± 0.10 g (±SD) were randomly assigned to one of seven triplicate groups and fed a non-GABA supplemented diet (CON, with 92 mg/kg GABA content), a positive control with 4 g/kg oxytetracycline (OTC), and five other diets supplemented with 50, 100, 150, 200 and 250 mg/kg GABA (corresponding to a total GABA content of 154, 229, 282, 327 and 352 mg/kg, respectively). Growth, blood chemistry, nonspecific immunity, digestive enzyme activity and disease resistance were assessed. The results showed that 100 and 150 mg/kg GABA supplementation consistently yielded significant improvements (p < 0.05) in growth, intestinal amylase, serum lysozyme, and survival against infection with Streptococcus iniae. Based on polynomial analysis, the optimal supplementation level was determined to be 237 mg/kg. These results support GABA as an important functional feed additive in juvenile olive flounder.

An 8-week feeding trial was conducted to evaluate the effects of dietary γ-aminobutyric acid (GABA) on growth performance, immune response, and disease resistance for juvenile whiteleg shrimp, Litopenaeus vannamei. Five isonitrogenous diets were formulated by supplementing 0 (CON), 50 (GABA50), 100 (GABA100), and 300 (GABA300) mg of GABA and 4 g of oxytetracycline (OTC) per kilogram of diet. A total of 225 juvenile whiteleg shrimp with an initial weight of 2.97 ± 0.06 g were randomly distributed and reared in 15 aquaria as triplicates. After 8 weeks of the feeding trial, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio of shrimp fed GABA100 were significantly higher than those of shrimp fed CON, GABA50, and GABA300 diets ( P < 0.05 ). However, there were no significant differences among shrimp fed CON, GABA50, GABA300, and OTC diets ( P > 0.05 ). After nine days of challenge test with Vibrio alginolyticus, the average cumulative survival rate of shrimp fed GABA50, GABA100, and OTC was significantly higher than that of shrimp fed GABA300 and CON diets ( P < 0.05 ). These results may suggest that 100 mg dietary GABA supplementation (including endogenous GABA, 175.6 mg/kg diet) per kilogram of diet could be the optimum dietary level to replace antibiotics and improve growth performance and disease resistance in whiteleg shrimp L. vannamei.

This study examined the effects of feeding fermented tuna by-product (FTBP) on the growth, non-specific immune response, liver and intestinal morphology, and disease resistance of olive flounder Paralichthys olivaceus. Olive flounders (n = 20; 2 g) were randomly assigned into four dietary groups in triplicates. Fish were fed four test diets (50% crude protein; 10% crude lipid) for 10 weeks in which unprocessed tuna by-product (TBP) meal was replaced (on a protein basis) with 0% (FTBP0 as the control diet), 15% (FTBP15), 30% (FTBP30), and 60% (FTBP60) of FTBP protein. Results showed that growth performance, blood parameters, and proximate composition were not influenced by FTBP inclusion. Non-specific immune parameters such as superoxide dismutase activity in the FTBP30 and FTBP60 groups were significantly higher than in the FTBP15 and the control groups, whereas lysozyme and myeloperoxidase activities were not different. Liver histopathology revealed normal architecture in groups fed FTBP0 and FTBP15 diets although mild alterations were noted in the FTBP30- and FTBP60-fed groups. Intestinal villi height and muscular thickness were not significantly altered with FTBP inclusion. Moreover, higher cumulative survival rate was observed in the FTBP60-fed group than fish fed with the other diets following the 13-day challenge with E. tarda. Together, these results demonstrate that fermented tuna by-product meal could be included at 60% in olive flounder diets.

This study was performed to evaluate the effects of dietary probiotics on growth, non-specific immune responses and disease resistance in olive flounder, Paralichthys olivaceus. During 8 weeks, the fish were fed the five experimental diets such as a basal commercial diet (CON), oxytetracycline (OTC) and three basal diets containing Bacillus subtilis (BS), a commercial microbial product (CES) and a mixture of yeast and bacterium (PI), respectively. Fish fed all the probiotics diets and OTC showed a significantly higher growth than fish-fed CON (P < 0 center dot 05). Fish-fed PI had a significantly higher nitroblue tetrazolium activity, whereas fish-fed CES showed a higher lysozyme level (P < 0 center dot 05). A 7-day challenge test also showed that fish-fed PI had a cumulative survival rate equivalent to that of fish-fed OTC (P < 0 center dot 05). Moreover, the diet (PI) appeared to increase the diversity of microbial community in the fish. All these results suggest that the probiotics diet could function as a potential antibiotic replacer in the olive flounder. Significance and Impact of the Study This study is unique in revealing that a diet mixture of yeast, Groenewaldozyma salmanticensis and bacterium Gluconacetobacter liquefaciens can enhance growth, innate immunity and diversity of microbial community including dominant species in the olive flounder. All these indicate that the diet mixture could function as a potential antibiotic replacer in one of the most commercially important fisheries in South Korea.

An eight-week feeding trial was conducted to evaluate the effects of different dietary probiotic supplements in juvenile whiteleg shrimp, Litopenaeus vannamei. A basal control diet without probiotics (CON), and five other diets by supplementing Bacillus subtilis at 107 CFU/g diet (BS7), B. subtilis (BS8), Pediococcus pentosaceus (PP8), and Lactococcus lactis (LL8) at 108 CFU/g diet, and oxytetracycline (OTC) at 4 g/kg diet were used. Whiteleg shrimp with initial body weights of 1.41 ± 0.05 g (mean ± SD) were fed with these diets. Growth of shrimp fed BS8 and LL8 diets was significantly higher than those of shrimp fed the CON diet (p < 0.05). Superoxide dismutase activity in shrimp fed PP8 and LL8 diets was significantly higher than that of shrimp fed the CON diet (p < 0.05). Lysozyme activity of shrimp fed probiotics and OTC diets significantly improved compared to those on the CON diet (p < 0.05). The intestinal histology showed healthier guts for shrimp fed the probiotic diets (p < 0.05). Immune-related gene expression in shrimp fed BS8, PP8 and LL8 diets was recorded as significantly higher than that of shrimp fed CON and OTC diets (p < 0.05). Also, results of the challenge test for 7 days and the digestive enzyme activity of shrimp fed BS8, PP8, and LL8 were significantly improved compared to those on the CON diet (p < 0.05). Therefore, these results indicated that L. lactis at 108 CFU/g could be an ideal probiotic for whiteleg shrimp, and also B. subtilis WB60 and P. pentosaceus at 108 CFU/g could improve the growth, immunity, histology, gene expression, digestive enzyme activity, and disease resistance, while replacing antibiotics.

This study evaluated the effects of replacing fish oil (FO) with beef tallow (BT) in juvenile olive flounder, Paralichthys olivaceus (3.93 +/- 0.07 g), over 8 weeks. Seven diets, consisting of 0, 25, 50, 75, and 100% replacement of FO with BT and 63 and 75.9% replacement supplemented with docosahexaenoic acid (DHA) at 0.9 and 1.1% of 100 g diet, respectively, were distributed into 21 tanks in a semi-recirculation system with 15 fish per tank. The replacement of FO with BT at the given levels showed no significant changes (p > .05) in growth performance and whole-body proximate composition. Fish fed the diet of 75.9% replacement with 1.1% DHA supplementation showed the best performance in these measurements among the treatments. Plasma glutamic pyruvic transaminase, cholesterol, high- and low-density lipoproteins, and total protein were not significantly influenced by the replacement of FO with BT. The FO replacement generally resulted in a reduction of eicosapentaenoic acid, DHA, and n-3/n-6 polyunsaturated fatty acid ratio in the whole body, whereas the DHA supplementation recovered the level of DHA and the n-3/n-6 ratio to those observed in the group fed the 0% replacement diet. Taken together, BT along with DHA supplementation can potentially be a cost-effective alternative for FO in olive flounder culture.

An eight-week feeding trial was conducted to evaluate the contribution of biofloc on dietary lipid requirement in whiteleg shrimp Litopenaeus vannamei. Five diets with graded levels of dietary lipid (45, 60, 90, 120 and 150 g/kg) were fed to juvenile shrimp. Final weight, weight gain and specific growth rate of shrimp fed diets with 60, 90 and 120 g/kg lipid levels were significantly higher than those of shrimp fed diets with lipid levels 45 and 150 g/kg (p < .05). Feed efficiency and protein efficiency ratio of shrimp fed 60, 90 and 120 g/kg were higher than those fed 150 g/kg diet. Plasma total cholesterol and triglyceride levels were lower in shrimp fed 45 g/kg compared with those fed the 90 g/kg (p < .05). Also, lysozyme activity for 90 g/kg group was higher than the 15 g/kg group. Hepatopancreas lipase and amylase activities of shrimp fed 90 and 120 g/kg diets were significantly higher than those of shrimp fed 45 and 150 g/kg diets. Broken-line regression analysis for weight gain indicated that the dietary lipid requirement of whiteleg shrimp juveniles reared in a biofloc system was estimated to be higher than 56 g/kg but <60 g/kg.

An eight-week feeding trial was conducted to evaluate the effects of a basal control diet (CON), Bacillus subtilis at 107 (BS7) and at 108 CFU/g diet (BS8), Lactococcus lactis at 107 CFU/g (LL7) and at 108 CFU/g diet (LL8), and oxytetracycline (OTC) at 4 g/kg diet on Nile tilapia. Fish with initial body weight of 2.83 ± 0.05 g (mean ± SD) were fed two times a day. Weight gain, specific growth rate, feed efficiency, protein efficiency ratio and lysozyme activity of fish fed BS8, LL8 and LL7 diets were significantly higher than those of fish fed CON diet (p < 0.05). Superoxide dismutase and myeloperoxidase activity of fish fed BS8, LL8, BS7, LL7 and OTC diets were significantly higher than those of fish fed CON diet. Intestinal villi length and muscular layer thickness of fish fed BS8, LL8 and LL7 diets were significantly higher than those of fish fed CON and OTC diets. Also, heat shock protein 70 (HSP70), interleukin (IL-1β), interferon-gamma (IFN-γ) and tumour necrosis factor (TNF-α) gene expression of fish fed BS8 and LL8 diets were significantly higher than those of fish fed CON diet. After 13 days of challenge test, cumulative survival rate of fish fed BS8 and LL8 diets were significantly higher than those of fish fed CON, BS7 and OTC diets. Based on these results, B. subtilis and L. lactis at 108 (CFU/g) could replace antibiotics, and have beneficial effects on growth, immunity, histology, gene expression, and disease resistance in Nile tilapia.

A 12-week feeding trial was conducted to investigate the effects of two dietary probiotics; Bacillus subtilis KCTC 2217 or Bacillus licheniformis KCCM 11775 with two prebiotics; mannan oligosaccharide (MOS) or fructooligosaccharide (FOS) in Japanese eel. Fish averaging 12.8 +/- 0.47 g (mean +/- SD) were randomly distributed into five treatments with triplicate tanks. A basal control diet (CON) and four synbiotic diets supplementing B. subtilis + MOS (BSM), B. subtilis + FOS (BSF), B. licheniformis + MOS (BLM), and B. licheniformis + FOS (BLF). Weight gain and specific growth rate of fish fed all synbiotic diets were higher than those of fish fed CON. Immune-related gene expression of heat shock protein 70 and immunoglobulin M of fish fed BSF and BLM were significantly higher than those of fish fed CON. Fish fed BSF and BLM had significantly higher intestinal villi length than those of fish fed BLF and CON (p < .05). Disease resistance against Aeromonas hydrophila of fish fed all synbiotic diets were significantly higher than those of fish fed CON (p < .05). Therefore, these results indicated that dietary B. subtilis with FOS (BSF) and B. licheniformis with MOS (BLM) could have beneficial effects on intestinal morphology, and immune-related gene expression in Japanese eel.

High demand and low supply of fishmeal due to overexploitation of fisheries resources have resulted in a dramatic increase in the price of this ingredient. Olive flounder (Paralichthys olivaceus) commercial feed contains approximately 60% fishmeal and limited success has been achieved in identifying sustainable alternative protein sources for this species. An on-farm feeding trial was conducted to compare a basal diet containing 65% as the control (CONT) with two experimental diets replacing 10% of fishmeal by animal protein (AP10) or 20% of fishmeal by animal and plant protein (APP20). Sub-adult olive flounder averaging 327 ± 9.3 g (mean±SD) were fed one of the three diets in triplicate groups for 16 weeks. Weight gain, specific growth rate, feed efficiency, protein efficiency ratio, and survival were not significantly different among fish fed all the experimental diets (P > 0.05). Also, non-specific immune responses (superoxide dismutase and lysozyme activity), serum biochemical parameters, and intestinal villi length were not significantly different among fish fed all the experimental diets (P > 0.05). Therefore, based on growth performance, non-specific immune responses, serum biochemical parameters, and intestinal histology, dietary animal and plant protein mixtures could replace up to 20% of fishmeal in the diet of sub-adult olive flounder.

A 12-week feeding trial was conducted to evaluate the synergistic effects of dietary vitamin E, alpha-Tocopheryl acetate (alpha-TA) and arachidonic acid, 20:4n-6 (ARA) on non-specific immune responses and tissue concentrations in female Japanese eel broodstock, Anguilla japonica. Four experimental diets (in a 2 x 2 factorial design) were formulated to contain two different levels of alpha-TA and ARA. A basal commercial diet without supplementation was used as the control (E(0)ARA(0)) with three other diets being formulated by addition of 200 mg alpha-TA kg(-1) (E(200)ARA(0)), 5 mg ARA kg(-1) (E(0)ARA(5)), and 200 mg alpha-TA + 5 mg ARA kg(-1) (E(200)ARA(5)). Four triplicate groups of 10 fish averaging 279 +/- 9.0 g (mean +/- SD) were randomly assigned to twelve 150-L tanks with a constant flow rate of 4 L min(-1). At the end of the trial superoxide dismutase (SOD) activity of fish fed E(200)ARA(5) were significantly higher than those of fish fed E(0)ARA(0) and E(200)ARA(0) (P > .05). Myeloperoxidase (MPO) and Lysozyme activities showed a similar trend with SOD activity, though there were no significant differences among the activities of fish fed experimental diets (P < .05). Liver and ovary alpha-TA concentrations of fish fed 200 mg alpha-TA kg(-1) diets (E(200)ARA(0) and E(200)ARA(5)) were significantly higher than those of fish fed non-alpha-TA supplemented diets (E(0)ARA(0) and E(0)ARA(5)). Liver ARA concentrations of fish fed 200 mg alpha-TA kg(-1) diets (E(0)ARA(5) and E(200)ARA(5)) were significantly higher than those of fish fed non-ARA supplemented diets (E(0)ARA(0) and E(200)ARA(0)). These results indicate that the dietary supplementation of alpha-TA and ARA has synergistic effects on nonspecific immune responses such as SOD activity. Furthermore, significantly higher tissue concentrations of alpha-TA, with regard to ovarian tissue, and both alpha-TA and ARA in liver tissue affirm a linear relationship with the level dietary supplementation in female Japanese eel broodstock.

In an eight-week feeding trial, encapsulated sodium butyrate (ESB), gamma-aminobutyric acid (GAB), selenium-yeast (SeY), yeast extract nucleotides (YEN), yucca meal (YUM), song-gang stone (SGS) and protease (PRT) were evaluated as functional feed additives in a low fishmeal (FM) diet for olive flounder Paralichthys olivaceus. Eight experimental diets were fed to 5.26 ± 0.17 g (mean ± SD) juvenile olive flounder in triplicates. A low-FM basal diet without feed additive was considered as control (CON); seven other diets were prepared by adding 4 g ESB, 158 mg GAB, 2 g SeY, 4 g YEN, 1.5 g YUM, 4 g SGS, and 175 mg PRT per kg of basal diet. Weight gain, specific growth rate, feed efficiency, and protein efficiency ratio of fish fed diets YEN, GAB, and SGS were significantly higher than those of fish fed CON diet (P < .05). Superoxide dismutase activity of fish fed YEN and myeloperoxidase (MPO) and nitroblue tetrazolium (NBT) of fish fed YEN, GAB, SGS, ESB, and YUM were significantly higher than those of fish fed CON diet. Whereas, there were no significant differences in non-specific immune responses among fish fed YEN, GAB, SGS, ESB, and YUM and diets (P > .05). Heat shock protein 70 gene expression of fish fed YEN and SeY was significantly higher than those of fish fed the CON diet. Intestinal villi length of fish fed YEN, GAB, SGS, and ESB was significantly higher than those of fish fed CON. Also, intestinal trypsin activity of fish fed YEN, GAB, SGS, ESB, and PRT was significantly higher than those of fish fed CON diet (P < .05). After seven days of challenge test, fish fed diets YEN, GAB, SGS, PRT, and YUM had higher cumulative survival than those of fish fed CON diet. In conclusion, YEN, GAB, and SGS could have beneficial effects on growth and feed utilization performance, MPO and NBT activity, intestinal villi length, intestinal trypsin activity, and cumulative survival of olive flounder fed low-FM diets.

Olive flounder (Paralichthys olivaceus) also referred to as bastard halibut is a marine carnivorous species with great commercial value. The production of olive flounder has been dominated by aquaculture with 43 thousand tons of production in 2017 compared to fisheries with only 10 thousand tons in the same year. But despite the high market demand for this species, aquaculture production has not increased accordingly within the last decade. The development of olive flounder aquaculture has been facing several drawbacks such as improper feed formulations, dependence on unreliable ingredients (e.g. fish meal and fish oil), disease outbreaks, and excessive use of harmful antibiotics. All these factors are major impediments in the sustainable development of olive flounder aquaculture. A great body of research has been conducted to understand the nutrient requirements of olive flounder while finding alternative protein sources in the diet. Also, several feed additives have been successfully tested as immunostimulants in olive flounder. All these findings are thoroughly discussed in this review, therefore, the information can be utilized by the industry and academic societies.

Six different types of solid state fermented plant proteins and soy protein concentrate were evaluated as fish meal replacers in whiteleg shrimp, Litopaeneus vannamei. In the first experiment, eight experimental diets consisted of a control diet without fish meal replacement (CON), and seven other diets replacing 30 % of fish meal with fermented soybean meal with Bacillus subtilis (FSMB), sterilized FSMB (FSMBS), fermented soybean meal and corn gluten meal with B. subtilis (FSCB), sterilized FSCB (FSCBS), fermented soy protein concentrate with B. subtilis (FSPB), fermented soybean meal with lactic acid bacteria (FSML), and soy protein concentrate (SPC). At the end of eight weeks, weight gain, specific growth rate and serum lysozyme activity of shrimp fed FSMB and FSCB diets were significantly higher than those of shrimp fed CON and FSML diets (P < 0.05). Feed efficiency and protein efficacy ratio of shrimp fed diets FSCB and FSCBS were significantly higher than those of shrimp fed the FSPB diet. Total intestinal B. subtilis count of shrimp fed FSMB, FSCB and FSPB diets were significantly higher than those of shrimp fed the other diets. After eight days of challenge test against Vibrio parahaemolyticus, average cumulative survival rate of shrimp fed diet FSCB was significantly higher than those of shrimp fed CON, SPC, FSMBS, FSCBS and FSML diets. In the second experiment, CON, FSMB, FSCB and FSPB diets, with (O) and without (X) bacterial water treatments were used for four weeks. Total ammonia nitrogen and NO2-N showed significantly lower values for FSCB(O) and FSPB(O) tanks compared to the CON(X) tank (P < 0.05). Total water B. subtilis counts, after 2 and 4 weeks, were significantly lower for both CON(O) and CON(X) tanks compared to all other tanks (P < 0.05). These results indicate that fish meal replacement with FSCB can improve growth, feed utilization, immune response and disease resistance in whiteleg shrimp while improving the water quality indices when administered with bacterial water treatment.

BACKGROUND Bioprocessing of plant feedstuff can be a novel approach for reducing the overwhelming dependence on fish meal in aquaculture. The objective of this study was to evaluate the performance of Pacific white shrimp Litopenaeus vannamei fed solid-state fermented protein concentrates in order to replace fish meal in the diet. RESULTS In the first trial, a group of 15 shrimp (average 3.88 g) were randomly distributed into aquaria in triplicate according to the experimental diets. Ten isonitrogenous (400 g kg(-1) CP) and isolipidic (90 g kg(-1) CL) diets were formulated to contain high-protein fish meal (HFM) and low-protein fish meal (LFM), and four types of bioprocessed protein concentrates (BPCs) as a replacement of fish meal (BPC-A, -B, -C and -D) each at 30% and 50% FM replacement levels. BPC-A was a solid-state fermented mixture of soybean and corn gluten meals; BPC-B was pre-treated acid-hydrolyzed BPC-A; BPC-C and BPC-D were BPC-A + 2% shrimp soluble extract (SSE) and BPC-B + 2% SSE, respectively. After 8 weeks, shrimp fed the HFM, BPC-B, BPC-C and BPC-D diets showed significantly higher growth performance at 30% FM replacement than those of shrimp fed the BPC diets at 50% FM replacement. Interestingly, shrimp fed the BPC-D diet could replace up to 50% FM replacement. In the second trial, the results show that apparent digestibility coefficients of feeds and apparent digestibility coefficients of ingredients for crude protein were significantly higher in fish fed the BPC-B, BPC-C and BPC-D diets. CONCLUSIONS The results demonstrated successful partial replacement of high-protein fish meal using high-quality fermented protein concentrates from plant sources. (c) 2019 Society of Chemical Industry

An eight-week study was conducted to determine the optimum dietary choline level in juvenile olive flounder, Paralichthys olivaceus. Seven diets were prepared to contain 0, 250, 500, 750, 1,000, 2,000 and 3,000 mg/kg diet. Juveniles (5.9 +/- 0.03 g; 5.5 +/- 0.4 cm; mean +/- SD) were randomly distributed into 21 tanks (25 fish/tank) and fed one of the diets in triplicates. Survival rate of fish fed the diet containing the lowest choline level was significantly lower than those of fish fed the other diets (p < 0.05). Final body weight, weight gain, specific growth rate, feed efficiency and protein efficiency ratio significantly increased with increasing choline levels up to 1,000 mg/kg diet. Whole-body protein and lipid contents increased in accordance with choline levels up to 750 mg/kg diet, beyond which they plateaued. Liver and muscle lipid contents elevated with increasing choline levels up to 2,000 mg/kg diet. Plasma cholesterol esters, triglycerides, cholesterol and total lipids were significantly influenced by the graded choline levels; however, responses of those indices were not identical. Broken-line analyses of weight gain and liver choline concentrations responding to the graded choline levels revealed that choline requirements of the juvenile flounder could be between 847 and 1,047 mg/kg diet.

This study was conducted to evaluate the effects of replacing dietary fish oil (FO) with poultry oil (PO) in a diet for olive flounder, Paralichthys olivaceus. In the experiment, triplicate groups of 15 juvenile olive flounder averaging 3.93±0.07g (mean±SD) were fed one of the seven experimental diets. Seven diets were formulated to replace FO with PO at 0% (PO₀), 25% (POSUB25/SUB), 50% (POSUB50/SUB), 75% (POSUB75/SUB), and 100% (POSUB100/SUB). Additionally, two treatments were replaced FO with PO at 68.6% and docosahexaenoicacid (DHA) at 14.4% (BTSUB68.6/SUBDSUB14.4/SUB), and PO at 82.8% and DHA 17.2% (BTSUB82.8/SUBDSUB17.2/SUB) of diet, respectively. At the end of 8-week feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed PO 50% diet were significantly lower than those of fish fed PO 75% and PO 100% diets (P0.05). However, WG and SGR of fish fed control diet were not significantly different from those of fish fed the other diets. There were no significant differences in feed efficiency and protein efficiency ratio of fish fed the experimental diets. Survival rate (%) of fish fed the all diets were not significantly different. Replacing FO with PO had no adverse effects on measured indices of serological parameters and whole body composition (P0.05) after the 8-weeks feeding trial. Reducing FO up to 75% significantly decreased whole-body EPA, DHA and total n-3 fatty acids (P0.05) relative to control group; while, whole-body DHA had no significant differences between control and DHA supplemented group (P0.05).BR Based on the results of growth performance, we concluded that PO can be potentially replaced with FO up to 100% in the diet containing 53.9% of fish meal for juvenile olive flounder.

The present study was conducted to evaluate the effects of different dietary gamma-aminobutyric acid (GABA) levels in Nile tilapia, Orechromis niloticus. Six groups of fish averaging 3.03 +/- 0.07 g (mean +/- SD) were randomly distributed in 18 rectangular tanks in triplicates. A basal diet without GABA supplementation was used as a control (CON), and the other five diets were prepared by adding 75 mg GABA (GABA(144)), 75 mg GABA +50 mg heat-killed Lactobacillus paracasei (GABA(189)L), 150 mg GABA (GABA(197)), 150 mg GABA +50 mg heat-killed Lactobacillus paracasei (GABA(242)L), and 600 mg GABA (GABA(507)) per kg of diet. Actual GABA compositions for CON, GABA(144), GABA(189)L, GABA(197), GABA(242)L and GABA(507) diets were 96, 144, 189, 197, 242 and 507 mg kg(-1), respectively. After 8 weeks of experiment, weight gain, specific growth rate, feed efficiency and protein efficiency ratio of fish fed GABA(189)L were significantly higher than those of fish fed CON and GABA(5.7) diets (P < .05). Serum glutamic oxaloacetic transaminase level of fish fed GABA(144) and GABA(189)L was significantly lower than those of fish fed diets GABA(197) and GABA(507) (P < .05). Serum total protein of fish fed GABA(189)L was significantly higher than those of fish fed CON, GABA(144), GABA(197) and GABA(242)L. Also, superoxide dismutase activity of fish fed the CON diet was significantly lower than those of fish fed all the other diets. Broken line analysis for weight gain showed the optimum dietary GABA level could be 158 mg kg(-1) diet. In the current study, it could be concluded that addition of 75 mg kg(-1) of GABA with dietary heat-killed Lactobacillus paracasei (diet GABA189L) could increase growth and feed utilization performance, serum total protein and superoxide dismutase activity of juvenile Nile tilapia.