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We evaluated the effects of diets incorporating the red algae Pyropia yezoensis, prepared by several different extraction methods, on the growth of juvenile Japanese flounder Paralichthys olivaceus. We assessed growth performance, as well as the levels of amino acids, fatty acids, insulin-like growth factor I (IGF-I) and interleukins (ILs). Four experimental diets were developed based on different methods of processing P. yezoensis. A commercial feed, laver powder (P), high-pressure heat extraction of laver (HPHE) and acid hydrolysis extraction of laver were used as the experimental diets. Three experimental replicates were established for each diet (40 fish/group, body weight 123.7 ± 1.1 g), and the fish were fed for 6 weeks. We found no significant differences in weight gain, specific growth rate or feeding efficiency among the groups ( P > 0.05); however, the fish fed HPHE had the greatest growth performance. Fish fed the laver extracts exhibited the highest protein efficiency ratio compared with the control and P groups. The experimental groups fed P. yezoensis extracts had significantly higher levels of IGF-I ( P < 0.05) than those of the control group. High levels of IL-2 were found in the P and HPHE groups, IL-12 in the HPHE group, and IL-6 in all experimental groups. Therefore, these results suggest that a P. yezoensis extract improved the growth performance and immunity of Japanese flounder. In particular, the high-pressure heating process was a useful extraction method for preparing a P. yezoensis extract, which had beneficial effects as a dietary supplement in Japanese flounder. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the effects of dietary protein levels on growth, biometrics, hematology and body composition in juvenile parrot fish Oplegnathus fasciatus. Fish averaging 7.1 ± 0.06 g (mean ± SD) was randomly distributed into 15 net cages (each size: 60 × 40 × 90 cm, W × L × H) as groups of 20 fish. Five isocaloric diets (16.7 kJ/g energy) were formulated to contain crude protein levels (CP) as 35 (CP), 40 (CP), 45 (CP), 50 (CP) and 60 % (CP) in the diets. Fish were fed one of the experimental diets at apparent satiation twice a day in triplicate groups. At the end of 8-week feeding trial, weight gain (WG) of fish fed with CP and CP diets were significantly higher than those of fish fed with CP, CP and CP diets. Fish fed with CP, CP and CP diets had higher feed efficiency (FE) and specific growth rate (SGR) than those of fish fed with CP and CP diets. Protein retention efficiency (PRE) decreased with increase of dietary protein levels among fish fed with the experimental diets. Whole-body crude protein and lipid contents increased with the dietary protein level up to CP diet. In conclusion, analysis of variance (ANOVA) revealed that the optimum dietary protein level could be 50 % for maximum growth of juvenile parrot fish, while the broken-line analysis of WG suggested that the level could be 48.5 %, in a diet containing 16.7 kJ/g energy. [ABSTRACT FROM AUTHOR]

Abstract: This study was aimed to examine the effect of dietary glycoprotein extracted from the sea mustard Hizikia fusiformis (Phaeophyceae: Sargassaceae) as a dietary supplement on growth performance in association with somatotropin level, proximate compositions, and immunity in juvenile olive flounder Paralichthys olivaceus. Water–ethanol extracted glycoprotein from H. fusiformis was supplemented to three fishmeal-based diets at the concentration of 0, 5, and 10gkg−1 diet (designated as H0, H5, and H10, respectively). After a 12week-long feeding trial, growth performance and biochemical responses were analyzed including proximate composition, and whole body amino acids and fatty acids. We also measured plasma insulin like growth factor (IGF), IGF-binding protein (IGFBP) and interleukin (IL). The fish fed H5 showed the greatest weight gain among the dietary treatments. In parallel with the growth, the fish fed the diets containing H. fusiformis glycoprotein showed an increased plasma IGF-I activity and increased expression of 43-kDa IGFBP-3 compared to that in the control, whereas an opposite trend was observed for 34-kDa IGFBP-1. Although no differences were found in the level of whole body linoleic acid (C18:2n−6) and linolenic acid (C18:3n−3) among treatments, increases in arachidonic acid (ARA, C20:4n−6), eicosapentaenoic acid (EPA, C20:5n−3) and docosahexaenoic acid (DHA, C22:6n−3) were observed in fish fed H5 compared to control. IL-2 and -6 levels increased significantly in fish fed H10 compared to those in the control indicating increased immunity. These results suggest that supplementation of H. fusiformis glycoprotein in fish diet may be beneficial for fish growth and immunity in juvenile olive flounder. [Copyright &y& Elsevier]

This experiment was conducted to compare l-ascorbyl-2-monophosphate-Ca (AMP-Ca) with l-ascorbyl-2-monophosphate-Na/Ca (AMP-Na/Ca) for supplying the dietary vitamin C for juvenile Korean rockfish (Sebastes schlegeli). Fish were fed 1 of 11 semi-purified diets containing equivalent of 0, 50, 100, 200, 400, and 800 mg ascorbic acid (AA)/kg diet in the form of AMP-Ca or AMP-Na/Ca for 12 weeks. After 12 weeks of the feeding trial, weight gain (WG), feed efficiency (FE) of fish fed with the control diet (vitamin C-deficient diet) were significantly lower than those of fish fed with the vitamin C-supplemented diets in either form (P<0.05). WG of fish fed with AMP-Na/Ca 400, AMP-Na/Ca 800, AMP-Ca 400 and AMP-Ca 800 diets were significantly higher than those of fish fed with the control diet, AMP-Na/Ca 50, AMP-Ca 50 and AMP-Ca 100 diets (P<0.05). In general, there was no significant difference between AMP-Ca diets and AMP-Na/Ca diets at the same supplementation levels. By the end of the 9th week, fish fed with the control diet began to show the initial vitamin C deficiency signs such as anorexia, erratic swimming behavior, darkening in skin color and reduced growth.The ascorbic acid concentrations in fish muscle and liver increased with the increase of the vitamin C supplementation levels in fish diets regardless of which kind of vitamin C source used. There were no significant differences in ascorbic acid concentrations in liver and muscle of fish between the two vitamin C sources at the same supplementation level.These results indicate that AMP-Ca is a bioavailable form of vitamin C source for Korean rockfish and it has the antiscorbutic activity equal to AMP-Na/Ca.Broken-line analysis of weight gain indicated that the dietary vitamin C requirement of Korean rockfish was 106 mg AA/kg diet based on the pooled WG of fish fed with the AMP-Na/Ca and AMP-Ca diets. However, based on the different forms of ascorbic acid, the vitamin C requirements were 101 and 112 mg AA/kg diet with the forms of AMP-Na/Ca and AMP-Ca, respectively. [Copyright &y& Elsevier]

An 11-week feeding trial was conducted to study the effects of the different levels of dietary vitamin C on growth, tissue ascorbic acid concentrations and histopathological changes in parrot fish. Casein and gelatin-based diets were formulated to contain 0, 60, 120, 240, 480 and 2000 mg l-ascorbic acid (AA) per kg diets on AA equivalent basis in the form of l-ascorbyl-2-monophosphate (AMP), 60 and 240 mg AA per kg diet as l-ascorbic acid. However, the analyzed AA levels were 0, 50, 100, 205, 426 and 1869 mg AA per kg diet in AMP supplemented diets; 36 and 149 mg AA per kg diet in l-ascorbic acid supplemented diets. Thus, the diets were designated as AA-free, AMP50, AMP100, AMP205, AMP426, AMP1869, AA36 and AA149. Fish averaging 3.9±0.06 g (mean±S.D.) randomly were fed the experimental diets in triplicate groups for 11 weeks. Weight gain (WG) of fish fed AMP50 and AA36 diets were significantly lower than those of the other groups, and fish fed AMP1869 diet showed a higher WG than did fish fed AMP50, AMP100, AMP205, AA36 and AA149 diets (P<0.05). However, there was no significant difference in WG between fish fed diets AMP426 and AMP1869, and among fish fed AMP100, AMP205, AMP426 and AA149 diets. Fish fed the AA-free diet began to show deficiency signs, such as retarded growth, darkening, anorexia and high mortality, after 3 weeks of feeding trial. After 6 weeks of the feeding trial, liver from fish fed the AA-free diet showed severe atrophy. By the end of the seventh week, all fish fed the AA-free diet were dead. Liver AA concentration from fish fed AMP50 diet was significantly lower than that from fish fed AMP205, AMP426, AMP1869 and AA149 diets, and fish fed AMP50, AMP100, AA36 diets showed a significant lower AA concentration in liver than did fish fed AMP205, AMP426 and AMP1869 diets.Broken line analysis of weight gain indicated that the dietary vitamin C requirement of parrot fish is 118±12 mg AA per kg diet in the form of l-ascorbyl-2-monophosphate for maximum growth. [Copyright &y& Elsevier]

Simple Summary: This study investigated the effects of three artificial diets used in aquaculture, two for rainbow trout and one for Atlantic salmon, on the growth rate, organ responses, gene expression and immune responses of parr juvenile Atlantic salmon. The diets differed with respect to their carbohydrate, protein and lipid levels, with the lipid levels being the main focus of this study. We found no significant differences in the growth, feed efficiency, immunity, histology or gene expression of Atlantic salmon parr between the rainbow trout and salmon feed groups. Therefore, rainbow trout feed, which has a relatively low lipid content, could be used as a rearing feed for juvenile parr-stage Atlantic salmon, bringing potential economic benefits. Lipids in fish diets provide energy and play important roles in immunity and metabolism. Atlantic salmon, a species that migrates from freshwater to seawater, requires high energy, especially during smoltification. Juvenile teleosts have low lipid requirements, and a high dietary lipid content is known to have negative effects on their growth and digestion. Therefore, this study evaluated the effect of two commercial rainbow trout feeds (low-lipid, 13.41% and 14.6%) on the growth and immune responses of early parr-stage Atlantic salmon compared to commercial salmon feed (high-lipid, 29.52%). Atlantic salmon parr (weight: 14.56 ± 2.1 g; length: 11.23 ± 0.44 cm) were randomly divided into three groups and fed either one of two commercial rainbow trout feeds (RTF1 and RTF2) or the commercial salmon feed (ASF) for 12 weeks. At the end of the feeding trial, growth, haematology, histology and gene expression analyses were performed. There were no significant differences in weight gain rates or feed efficiency between the groups (p > 0.05). Superoxidate dismutase, glutathione peroxidase, lysozyme and immunoglobulin M activities were not different among the experimental groups (p > 0.05). A histological examination of the liver and intestinal tissues showed no pathological symptoms of inflammatory response or lipid accumulation in any of the groups. In an intestinal transcriptome analysis using RNA-seq, the expression levels of several genes linked to lipids, immune-related proteins, cytokines and chemokines did not differ significantly between the groups (p > 0.05). Commercial rainbow trout feed with low lipid content has no clear negative impact on the development of Atlantic salmon during the early parr stage (14.5 to 39.6 g). This study provides basic information for the development of economical feed for early parr-stage Atlantic salmon. [ABSTRACT FROM AUTHOR]

The experiment was conducted to evaluate alternative protein ingredients in a low-fish meal (FM) diet for red seabream (Pagrus major). Twelve experimental diets were formulated. Control diet (CON) was designed to contain 60% FM. Other experimental diets were formulated by replacing 50% of FM from the CON with soy protein concentrate (SPC), corn gluten (CG), meat meal (MM), and/or chicken byproduct meal (CBM). Four diets were designed including one of SPC, CG, MM, or CBM as FM replacer and designated as SPC, CG, MM, and CBM. Six other diets were formulated by adding two ingredients as SPC and CG, SPC and MM, SPC and CBM, CG and MM, CG and CBM, or MM and CBM, and designated as SCG, SMM, SCM, CMM, CCM, and MCM, respectively. The 12th diet (MIX) was formulated by including SPC, CGM, MM, and CBM. Triplicate fish groups (50.2 ± 0.1 g) were hand-fed for 12 weeks. Weight gain (WG) of fish was significantly improved by MM and MCM diets compared to CG, SCG, CMM, and CCM diets. WG of CON, SPC, CM, SMM, SCM, and MIX groups were comparable with MM and MCM groups. The lowest WG was observed in CG and CMM groups. Feed efficiency (FE) was significantly higher in MM group compared to SPC, CG, SGC, and CMC groups. FE of MCM group was significantly higher than CG and SCG groups. Fillet linolenic acid (C18:2n–6) level in CG group was significantly higher than CON, MM, CM, SCM, CCM, and MCM groups. Serum lysozyme activity was significantly higher in MCM and MIX groups. Therefore, a high level of dietary CG reduces the growth performance and feed utilization of red seabream. A mixture of MM and CBM seems to be more efficient in replacing FM from red seabream diet. [ABSTRACT FROM AUTHOR]

Poly-γ-glutamic acid (γ-PGA) is an unusual anionic homopolyamide that is biodegradable, edible, and nontoxic. It has a wide variety of industrial applications depending on its combined cations, and molecular weight. In this study, extracellular viscous γ-PGA produced by halotolerant Bacillus sp. SJ-10 isolated from a traditional Korean salted-fermented seafood was purified and characterized. The physicochemical analysis indicated that the γ-PGA produced by Bacillus sp. SJ-10 consists primarily of d -glutamic acid residues combined with sodium cations. When batch fermentation was performed with 8% NaCl for 3 d, Bacillus sp. SJ-10 produced approximately 24.7 g/L γ-PGA with a molecular weight of approximately 400 kilodaltons (kDa). Under fermentation conditions with 6% NaCl, the maximum yield was 26.2 g/L regardless of the molecular weight. The γ-PGA sodium salt with a molecular weight of 400 kDa exhibited antioxidant activity by scavenging 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radicals and reducing molybdenum, with maximal scavenging activity at 0.5 mg/mL and reducing activity at 1 mg/mL (20 μg ascorbic acid-equivalent), respectively. These results suggest the potential use of γ-PGA in the food, cosmetic, and biomedical industries for its antioxidant qualities. Our results also provide an economical method for controlling the molecular weight of the γ-PGA produced. [ABSTRACT FROM AUTHOR]

Simple Summary: The marbled flounder (Pseudopleuronectes yokohamae) is a fish species with high commercial value in Korea and has been gaining attention as a new aquaculture target. To clarify the digestive physiology and feeding habits of the marbled flounder, this study conducted morphological, histological, and histochemical analyses of its digestive tract. In conclusion, the feeding habits of marbled flounder are close to those of carnivorous fish. In addition, we found that the marbled flounder has a stomach with a structure suitable for eating small amounts of hard food, and that most of its digestion takes place in the anterior intestine portion. Our study presents the histological and histochemical characteristics of the digestive tract of the marbled flounder, providing basic knowledge for both physiological and nutritional studies. This study investigated the morphological, histological, and histochemical characteristics of the digestive tract of the marbled flounder (Pseudopleuronectes yokohamae). The relative length of the gut of the marbled flounder digestive tract was 1.54 ± 0.10 (n = 20), and it had a simple stomach and 6–9 pyloric caeca. The mucosal folds of the marbled flounder digestive tract exhibited a general branched morphology. The thickness and mucosal fold length of the intestinal muscularis externa showed similar aspects in all areas. The thickness of the intestinal muscularis externa was the thickest in the posterior intestine portion, and the length of mucosal folds was the longest in the anterior intestine portion. It was indicated that food digested by gastric acid in the stomach moves to the anterior portion (including pyloric caeca) and mid portion of the intestine, ensuring effective stimulation of cholecystokinin (CCK)-producing cells. In addition, the distribution pattern of CCK-producing cells in the intestine was very similar to that of mucus-secreting goblet cells. The CCK-producing cells and goblet cells in the marbled flounder were well-adapted to promote optimal control of the digestive process. Based on the morphological and histochemical studies, it was concluded that the marbled flounder displays a digestive tract comparable to that of fish species with carnivorous habits. [ABSTRACT FROM AUTHOR]

Butylated hydroxytoluene (BHT) is a commonly used antioxidant added to animal/fish feed to limit lipid autoxidation and peroxidation. Although there have been reviews and reports of BHT toxicity in animals, limited information is available with respect to the toxic effects and accumulation of BHT due to oral exposure in aquaculture species. Therefore, 120 days of feeding trial was conducted to evaluate the effects of dietary BHT on the marine fish olive flounder Paralichthys olivaceus. Graded levels of BHT were added to the basal diet in increments of 0, 10, 20, 40, 80, and 160 mg BHT/kg, corresponding to 0 (BHT0), 11 (BHT11), 19 (BHT19), 35 (BHT35), 85 (BHT85), and 121 (BHT121) mg BHT/kg diets, respectively. Fish with an average weight of 77.5 ± 0.3 g (mean ± SD) were fed one of the six experimental diets in triplicate groups. Growth performance, feed utilization, and survival rate were not significantly affected by the dietary BHT levels among all experimental groups, whereas BHT concentration in the muscle tissue was found to increase in a dose-dependent manner up to 60 days of the experimental period. Thereafter, BHT accumulation in muscle tissue showed a declining trend among all treatment groups. Furthermore, the whole-body proximate composition, nonspecific immune responses, and hematological parameters (except triglycerides) were not significantly influenced by the dietary levels of BHT. Blood triglyceride content was significantly higher in fish fed the BHT-free diet compared to all other treatment groups. Thus, this study demonstrates that dietary BHT (up to 121 mg/kg) is a safe and effective antioxidant without exhibiting any adverse effects on the growth performance, body composition, and immune responses in the marine fish olive flounder, P. olivaceus. [ABSTRACT FROM AUTHOR]

Presents a correction for the article 'Long-term evaluation of extruded diets compared with raw fish moist diet for growing Korean rockfish, Sebastes Schlegeli (Hilgendorg)' by Kang-Woong Kim, Xiajie Wang, Se-Min Choi, Sungchul C. Bai, Youn-Hee Choi and Seong-Hee Choi which was published in volume 33, number 12 of the journal 'Aquaculture Research.' misspelling of authors' names.

Simple Summary: The global price of fish oil continued to increase due to a consistent downward production trend. Therefore, research on the replacement of fish oil is growing and the search for sustainable alternative sources in aquaculture. The present study was conducted to evaluate dietary microalgae, Schizochytrium sp. (SC) as fish oil replacer in rainbow trout, Oncorhynchus mykiss. Our results suggested that dietary SC is well-digested and could replace up to 80% of fish oil in the diet of rainbow trout without negative effects on growth and immune responses. The price of fish oil has reached a historical peak due to a consistent downward production trend, and therefore, the search for sustainable alternative sources has received great attention. This research was conducted to evaluate dietary micro-algae, Schizochytrium sp. (SC) as fish oil (FO) replacer in rainbow trout, Oncorhynchus mykiss. In the first trial, apparent digestibility coefficient (ADC) was 92.4% for dry matter, 91.4% for crude protein, and 94.2% for crude lipid in rainbow trout. In the second trial, six diets were formulated to replace FO at 0% (CON), 20% (T20), 40% (T40), 60% (T60), 80% (T80), and 100% (T100) with SC in the rainbow trout (3.0 ± 0.4 g, mean ± SD) diet. After eight weeks' feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of fish fed the T20 diet were significantly higher than those of fish fed other diets (p < 0.05). However, there were no significant differences in these parameters among those of fish fed CON, T40, T60, and T80 diets. Lysozyme activity of fish fed the T20 diet was significantly higher than those of fish fed other experimental diets (p < 0.05). After 10 days of disease challenge testing with pathogenic bacteria (Lactococcus garvieae 1 × 108 CFU/mL), the cumulative survival rate of fish fed the T20 diet was significantly higher than those of fish fed the CON, T80, and T100 diets. Therefore, these results suggest dietary microalgae SC is well-digested and could replace up to 80% of fish oil in the diet of rainbow trout without negative effects on growth and immune responses. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize the bacteria isolated from rockfish intestines and to investigate the effects of feed supplementation in rockfish aquaculture. Bacillus sp. KRF-7 isolated from the intestine of rockfish (Sebastes schlegelii) was demonstrated to be safe based on in vitro tests confirming the absence of hemolysis, cytotoxicity, and genes with toxigenic potential. In a feeding trial, providing a supplemental diet of 1 × 108 CFU g−1 Bacillus sp. KRF-7 was observed to positively alter the weight gain, specific growth rate, feed conversion ratio, and protein efficiency ratio of juvenile rockfish. KRF-7 supplementation showed positive regulation of nonspecific immune parameters, such as superoxide dismutase, lysozyme activity, and myeloperoxidase activity. This analysis also revealed a change in the composition of the intestinal microbiota at the phylum level from Proteobacteria to Firmicutes. In both the kidney and spleen, the expression levels of IL-10, NF-κB, and B cell activating factors in the KRF-7-supplemented group were significantly increased compared to those in the control group. Therefore, this study verified the safety of KRF-7 isolated from the intestine of rockfish and suggests that dietary supplementation with KRF-7 enhances the growth performance of rockfish and has beneficial effects on the regulation of the intestinal microbiota and immune response. • The probiotic properties of Bacillus sp. KRF-7 were investigated. • Dietary supplementation of KRF-7 upregulated the growth performance of rockfish. • Supplementation with KRF-7 modulated gut microbial community of rockfish. [ABSTRACT FROM AUTHOR]

Abstract: This study was conducted to investigate the influence of dietary lipid level and supplemental soy lecithin on growth, feed utilization and body composition of juvenile flounder reared at two suboptimal water temperatures, 12 and 17 °C. Three isonitrogenous (CP 50%) diets containing 1% squid liver oil (S7), 7% squid liver oil (S14), and a mixture of 2% soy lecithin and 5% squid liver oil (SL14) were formulated to obtain 7% and 14% of crude lipid. Triplicate groups of fish (6.3±0.2 g) were fed to apparent satiation twice a day for 60 days. Weight gain, daily feed intake, feed efficiency and protein efficiency ratio were significantly higher for fish reared at 17 °C than at 12 °C. Daily feed intake was significantly decreased with the increase of dietary lipid level at the same water temperature, but weight gain was not affected by dietary lipid composition. At 12 °C, feed efficiency and protein efficiency ratio were significantly higher for fish fed the S14 and SL14 diets than those of fish fed the S7 diet, while at 17 °C feed efficiency and protein efficiency ratio of fish fed the S14 diet, which were not significantly different from those of fish fed the SL14 diet, were significantly higher than those of fish fed the S7 diet. There were no significant effects of dietary lipid composition or temperature range on the whole body contents of moisture, crude protein, lipid or ash. Dietary lipid composition and temperature affected the fatty acid content of the polar lipid from the liver; and the n-3HUFA contents such as 20:5n-3 and 20:6n-3 were higher at 12 °C than at 17 °C. The results of this study indicate that an increase of dietary lipid level from 7% to 14% has beneficial effects on feed utilization of flounder when reared in suboptimal water temperatures. The increase of water temperature from 12 to 17 °C improved growth and feed utilization, but 2% soy lecithin had no substantial effect on growth and feed efficiency of juvenile flounder. [Copyright &y& Elsevier]

A long‐term feeding trials were conducted to evaluate the effect substituting dietary fishmeal with a mixture of plant and animal protein sources on growth, body composition and economic efficiency of young Korean rockfish (Sebastes schlegeli). A fishmeal‐based diet was designated the control (Con). Three among the other six diets, respectively, had 30%, 40% and 50% of its fishmeal replaced by a mixture of plant and animal protein sources (designated as FS30, FS40 and FS50 respectively), while the remaining three diets were FS30, FS40 and FS50 diets supplemented with L‐lysine and L‐methionine (FS30AA, FS40AA and FS50AA respectively). Three replicated groups of fish (initial body weight, 86 ± 1.9 g) were fed one of the seven diets for 30 weeks. By the end of the feeding trials, the survival rate of all experimental groups was over 92%. The final mean weight, weight gain, feed efficiency, protein efficiency ratio and condition factor of fish were not significantly affected by dietary treatments. Incidence cost of FS50 diet was significantly lower than Con diet. FS50 and FS40AA diets exhibited significantly higher profit index than the Con diet. FS40AA and FS50 diets were the best economically, followed by FS40, FS50AA, FS30, FS30AA and Con diets. These results suggest that the dietary fishmeal could be substituted with a mixture of plant and animal protein up to 50% in the diet without a reduction in growth and feed utilization of young Korean rockfish. Taking account of economic efficiency, the FS50 diet is recommendable for young Korean rockfish farming. [ABSTRACT FROM AUTHOR]

The present study examined the dietary substitution effect of chicken by‐product meal (CBM) for fish meal (FM) on growth, feed utilization, body composition, haematology and non‐specific immune responses of olive flounder, Paralichthys olivaceus. Six isonitrogenic and isolipidic experimental diets were prepared. The control (Con) diet contained 650 g/kg FM. One hundred, 200, 300, 400 and 500 g/kg FM were replaced with CBM, referred to as the CBM10, CBM20, CBM30, CBM40 and CBM50 diets, respectively. A total of 400 juvenile fish averaging 14.7 g was distributed into 20 tanks (20 fish/tank) and fed triplicate groups of each diet, except for quadruplicate groups for the Con and CBM30 diets twice daily to satiation for 8 weeks. Arginine, phenylalanine and threonine content of the experimental diets increased with dietary increased substitution of FM with CBM. The experimental diets did not affect survival, weight gain, specific growth rate, feed consumption and feed utilization of fish. The chemical composition, whole body amino acid profiles, haematological variables and non‐specific immune responses of fish were not changed by the experimental diets. These findings suggest that FM up to 500 g/kg can be substituted with CBM without retardation in growth, feed utilization, haematology and non‐specific immune responses of olive flounder. [ABSTRACT FROM AUTHOR]

The attractiveness of crude feed ingredients to olive flounder and effects of including feed ingredients showing strong feeding attractiveness in extruded pellet (EP) on performance of fish were determined. Four types of experimental EP were prepared to evaluate the effects of feed ingredient manipulation on performance of fish. Five per cent anchovy meal component of the control diet was substituted with an equal amount of jack mackerel meal, sardine meal and hydrolysed fish meal to create the JM, SM and HFM diets respectively. The diets were prepared in commercial form as EP. Jack mackerel meal produced the strongest feeding attractant responses of olive flounder, followed by sardine meal and hydrolysed fish meal. The greatest weight gain, feed consumption and condition factor (CF) were observed in fish fed the JM diet, followed by fish fed the SM, HFM and control diets, in that order in the 8‐week feeding trial. The dietary manipulation of feed ingredients performed in this study showed that the inclusion of ingredients with strong feeding attractiveness improved feed consumption and eventually accelerated the growth performance and CF of the fish. [ABSTRACT FROM AUTHOR]

A 12-week feeding trial was conducted to evaluate the effects of multi-strain probiotics (MSP) in a low fish meal (FM) diet on overall performance, gut microbiota, selected non-specific immune responses and antioxidant enzyme activities of olive flounder (Paralichthys olivaceus) juveniles. A total of 225 healthy olive flounders (initial mean body weight, 13.5 ± 0.01 g) were randomly separated into 3 groups of 75 fish, each group having three replicates of 25 fish; first group was fed with a FM-based control diet (Con), 2nd group was fed with a low-FM diet containing a blend of plant and animal protein meals replacing 30% of the FM protein (FM30), and 3rd group was fed with the FM30 diet supplemented with 108–109 CFU kg−1 of the MSP (Pro). With the exception of lipid retention, which was significantly lower in fish fed the FM30 diet compared to the other two treatments, no other statistically significant differences were recorded with respect to any of the other growth and nutrient utilization parameters. Myeloperoxidase and lysozyme activities of fish fed the Pro diet were much higher and significantly different than those of fish fed the FM30 diet. Glutathione peroxidase activity was significantly higher in Pro- than in Con-fed fish, which, in turn, was significantly higher than FM30-fed fish. Expression of immune-related genes including IL-1β, IL-6, and TNF-α was markedly upregulated in livers of the fish fed Pro diet compared to those fed the Con and FM30 diets. Furthermore, supplementation of MSP in FM30 diet enriched the Lactobacillus abundance in the fish gut as well as predictive gene functions in relation to lipid and carbohydrate metabolisms. These data suggested that the MSP could reduce the potential adverse effects of the low-FM diet and might be used as a healthy immunostimulant for olive flounder. • Low fishmeal diet (FM30) significantly affected the lipid retention of olive flounder. • The multi-strain probiotics (MSP) improved the activities of myeloperoxidase, lysozyme, and glutathione peroxidase. • The MSP supplement markedly upregulated the immune-related gene expression of IL-1β, IL-6, and TNF-α in the liver. • The MSP supplement enriched the predictive gene functions in relation to lipid and carbohydrate metabolisms. • The MSP could be used as a healthy immunostimulant for olive flounder. [ABSTRACT FROM AUTHOR]

Prebiotics, probiotics, and synbiotics are considered natural functional food ingredients and an alternative feeding strategy for immunomodulation and antibiotic eradication. Olive flounder (Paralichthys olivaceus) is commercially cultured in China, Japan, and Korea. Antibiotics used in flounder aquaculture produce antibiotic-resistant pathogens and residual effects on human. Prebiotics are non-digestible oligosaccharides, fermented by intestinal microbiota to produce short-chain fatty acids that bind G protein receptors. Probiotics are usually incorporated into the diet at a certain concentration to alter the intestinal microbial population through colonization or implantation. Synbiotics are combinations of prebiotics and probiotics that produce synergistically better benefits than separately. Previous studies on olive flounder have revealed that various types of immunostimulants, prebiotics, probiotics, synbiotics, and potentially immunoreactive feed additives can increase growth and feed utilization; cellular and humoral immunity; immune gene expression; blood/serum biochemistry; and infectious-disease resistance. Additive concentrations, their activity, and viability after feed storage and in the intestine, and interactions with the intestinal microbial community are major limiting factors. This review summarizes and discusses changes in growth and feed utilization, innate immunity, biochemical parameters, gene transcription, and disease protection in olive flounder after diet supplementation with various types of additives. It also indicates areas needing greater attention for future research. [ABSTRACT FROM AUTHOR]

Abstract Investigations were carried out to evaluate and quantify the effects of dietary supplementation with heat-killed (HK) Bacillus sp. SJ-10 (BSJ-10) probiotic (1 × 108 CFU g−1) on the growth and immunity of olive flounder (Paralichthys olivaceus). Flounder (averagely 9.64 g) were divided into two groups, and fed control and HK BSJ-10 (HKBSJ-10)-inoculated diets for 8 weeks. Investigations were carried out on growth and feed utilizations, innate immunity, serum biochemical parameters, microvilli length, and pro- and anti-inflammatory cytokine gene (tumor necrosis factor [TNF]-α, interleukin [IL]-1β, IL-6, and IL-10) transcriptions. Compared to control, HKBSJ-10 diet significantly (P < 0.05) enhanced weight gain and protein efficiency ratio, 1.17 and 1.11 folds respectively. Humoral innate immune parameters, lysozyme and superoxide dismutase in treatment group were also elevated by 1.34 and 1.16 folds. Similarly, an increased (P < 0.05) relative expressions of TNF-α, IL-1β, IL-6 were recorded in liver (2.71, 3.38, and 4.12 folds respectively), and gill (2.08, 1.98, and 1.81 folds respectively) than that of controls. Moreover, after challenge with Streptococcus iniae (1 × 108 CFU mL−1), the HKBSJ-10-fed group exhibited significantly higher protection (P < 0.05) against streptococcosis compared to controls, validating the observed changes in immune parameters and induction on the cytokine-encoding genes. Therefore, HKBSJ-10 increases growth, modulates innate immune parameters, and protects olive flounders against streptococcosis. Highlights • Heat killed Bacillus sp. SJ-10 (HKBSJ-10) positively improved growth and feed utilization in olive flounder. • HKBSJ-10 enhanced humoral innate immunity and pro-inflammatory cytokine transcriptions. • Administration of HKBSJ-10 could increase resistance against streptococcosis. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate Bacillus sp. SJ-10, isolated from traditional Korean seafood, as a probiotic. Strain SJ-10 was demonstrated to be safe, on the basis of in vitro tests confirming the absence of cytotoxicity, hemolysis, and genes with toxigenic potential, and was susceptible to antibiotics. It met the probiotic prerequisites of a spore count that remained almost constant, acid and bile tolerance under simulated gastrointestinal conditions, and significant adhesion to Caco-2 cells. Moreover, SJ-10 demonstrated beneficial properties as a probiotic: broad-spectrum antimicrobial activity, hydroxyl radical, antioxidant activity, production of functional enzymes such as β-galactosidase and phytase, and selective growth via β-glucan fermentation. The fish-feeding trial demonstrated that olive flounder fed diets containing SJ-10 alone or in combination with β-glucan exhibited significantly higher growth performance and pathogenic disease resistance compared with those fed diets containing β-glucan alone, indicating that SJ-10 diets exerted a beneficial effect as an antibiotic replacer in terms of growth performance and disease resistance in olive flounder. [ABSTRACT FROM AUTHOR]

Abstract Bacillus sp. SJ-10 (BSJ-10) was identified from traditional Korean fermented fish, the previously recognized prebiotic β-glucooligosaccharides (BGO), and their combination as a synbiotic were prepared to evaluate their individual and synergistic effects in olive flounder (Paralichthys olivaceus). Four diets (one control and three treatments) were formulated containing neither BSJ-10 nor BGO (control), 1 × 108 CFU g −1 BSJ-10 (BSJ-10), 0.1% BGO (BGO), and 1 × 108 CFU g−1 BSJ-10 + 0.1% BGO (BSJ-10 + BGO). Triplicates of 15 fish (weight 10 ± 0.25 g) were randomly allocated to the four diet groups and fed one of the diets for 8 weeks. At the end of the experiment, fish weight gain (WG), specific growth rate (SGR), feed conversion ratio, and protein efficiency ratio in BSJ-10, BGO and BSJ-10 + BGO diets were positively modulated (P < 0.05) compared with control. Specially, WG and SGR were significantly (P < 0.05) higher in BSJ-10 + BGO than that of BSJ-10 and BGO (individual component). The innate immune parameters such as respiratory burst, superoxide dismutase, and lysozyme activity (LSZ) of fish fed BSJ-10 and BSJ-10 + BGO (both groups) were significantly (P < 0.05) higher than the control. Moreover, myeloperoxidase activity (MPO) and LSZ of fish fed BSJ-10 + BGO were significantly higher compared with individual component. Compared with control, intestinal BSJ-10 content, expression of interleukin (IL)-1β in liver and kidney, and tumor necrosis factor (TNF)-α in liver were higher in both groups, but microvillus length was increased (P < 0.05) only in BSJ-10 + BGO. During in vivo challenge experiment with Streptococcus iniae (1 × 108 CFU ml−1), survival rate of fish was significantly higher in all treatment groups versus control. Moreover, in BSJ-10 + BGO, protection against S. iniae infection and transcription of TNF-α and IL-6 in gill were significantly (P < 0.05) higher than the individual component. Collectively, an improved WG, SGR, MPO, LSZ, transcription of IL-6 and TNF-α, and cumulative survival rate against streptococcosis clearly demonstrates a synergistic outcome of diet BSJ-10 + BGO as synbiotic in olive flounder. Highlights • Bacillus sp. SJ-10 (BSJ-10) is identified as a potential probiotic in olive flounder. • BSJ-10+β-glucooligosaccharides produce synergistic effects on growth and innate immunity. • Transcription levels of pro-inflammatory cytokines are upregulated by dietary synbiotic. • Dietary synbiotic is able to increase microvillus length in the intestine. [ABSTRACT FROM AUTHOR]

(1,3)(1,4)-β- d -glucan has been determined to have various beneficial effects due to its unique structure. β-glucooligosaccharides (β-GOS), which are hydrolysates of barley (1,3)(1,4)-β- d -glucan, provide a useful prebiotic material for selective growth of probiotic bacteria. In this study, recombinant β-1,3-1,4-glucanase (Bg1314) from Bacillus sp. SJ-10 (KCCM 90078) was immobilized on porous silica using glutaraldehyde as a crosslinking reagent to achieve efficient production of β-GOS. We investigated the effects of factors such as the amounts of enzyme and glutaraldehyde, reaction temperature, and pH on catalytic activity. Enzyme activity decreased sharply at high concentrations of glutaraldehyde, likely due to the reaction of glutaraldehyde with lysine residues at the catalytic site of Bg1314, because lysine-substituted Bg1314 retained its activity under the same conditions. Immobilized Bg1314 protein (ImBg1314) was stable over a wide range of pH and could be stored long term at 4 °C. The optimal conditions of ImBg1314 were similar to those of Bg1314. However, the optimal temperature of ImBg1314 differed from that of Bg1314. The products were β-GOS composed of 3- O -β-cellobiosyl- d -glucose and 3- O -β-cellotriosyl- d -glucose. After ImBg1314 was reused for 10 cycles, it retained 42% of its initial catalytic activity. This study showed that the Imbg1314 applied economical production of β-GOS. [ABSTRACT FROM AUTHOR]

Abstract: β‐Glucooligosaccharides (BGO), produced from barley β‐glucan, were used as a feed supplement (0.1%) for juvenile olive flounder (Paralichthys olivaceus) to identify and quantify its oral administration effects on innate immunomodulation and infectious disease protection. Juvenile flounders (14 ± 0.5 g) were divided into two groups fed either 0.1% BGO (treatment) or a standard diet (control) for 8 weeks. At the end of the experiment, investigation of the effects was carried out through systemic studies on growth performance, serum and mucus biochemical parameters, innate immunity, microvillus length, and relative pro‐inflammatory cytokine gene expression. The results demonstrated that the BGO diet produced slightly higher levels of growth performance, serum protein, microvillus length and pro‐inflammatory cytokine gene (tumour necrosis factor‐α, interleukin [IL]‐1β, and IL‐6) expression without any significant differences (p > .05). All innate immunity parameters were up‐regulated by BGO administration and, among these, respiratory burst, lysozyme and superoxide dismutase (SOD) were significantly different (p < .05). Fish in the both groups were challenged with Streptococcus iniae (1.35 × 108 CFU/ml), and BGO group was focused to confirm the promotion of innate immunity parameters. The results showed a significantly (p < .05) lower death rate compared with that of the control. Therefore, BGO could be used as a new prebiotic in future olive flounder aquaculture as well as to control streptococcosis. [ABSTRACT FROM AUTHOR]

Extrusion technology is known to enhance feed quality by controlling feed processing conditions. Although extrusion technology has been extensively used to improve livestock feed quality, research on its effects on quality in fish is lacking. Furthermore, studies on feed processing, the physical properties of feed produced using extruders, and the effects of extrusion on formulated feed quality remain scarce. Therefore, in this study, we investigated the effects of extrusion pressure and raw material particle size on the growth performance and digestive physiology of rockfish (Sebastes schlegeli). Experimental diets were prepared under different extrusion pressures by manipulating the screw speed [low pressure (LP), 1080 rpm/min; high pressure (HP), 620 rpm/min] and mean raw material particle sizes [small size (SS), 199.1 μm3; large size (LS), 1026.8 μm3] in a two-level factorial design. Four experimental diets (SS/LP, SS/HP, LS/LP, and LS/HP) were randomly assigned to 12 tanks (3 replicates), which were each stocked with 30 fish (initial mean body weight, 82.7 ± 0.2 g). After a 16-week feeding trial, observations showed that SS and LP enhanced fish weight gain and plasma growth-related hormone activity. In addition, SS and LP increased intestinal digestive activity in fish, positively affecting growth. These results indicate that manipulating physical pellet qualities by adjusting the feed ingredient extrusion pressure and raw material particle size can improve the growth performance and digestive physiology of rockfish, which should be considered in feed manufacturing. • Extrusion pressure and particle size improved rockfish growth rate and growth hormone activity. • Higher water absorption ability of feed was associated with better fish growth. • SS and LP enhanced fish weight gain and plasma growth-related hormone activity. • SS and LP increased the digestive activity of the intestines. [ABSTRACT FROM AUTHOR]

The aim of this study was to improve the stability of β-1,3-1,4-glucanase by substituting hydrophobic residue for specific amino acid. The results indicated that the catalytic efficiency, thermostability and halostability were enhanced simultaneously by replacement of Lys48 with Ala (K48A) or Leu (K48L). Comparison of kinetic parameters revealed that catalytic efficiency of mutants is enhanced as a result of the increase in substrate affinity. A great improvement in thermostability and halostability was observed. The half-lives of mutants significantly increased (up to ∼7-fold) at 60–70 °C. Moreover, relative enzymatic activities of mutants were observed more than 80% even in the presence of 30% NaCl, and half-lives were increased to 3-fold that of wild-type. Based on above results, when applied to ionic liquid, mutants were more active and stable compared to wild-type. These were the results from improvement of protein functions by the substitution of hydrophobic single residue in adjacent with forming carbohydrate binding cavity. Therefore, this report could be helpful for improvement of the enzyme property and for biotechnological application as well. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to evaluate the effects of dietary probiotics on growth performance and non-specific immune responses in starry flounder, Platichthys stellatus . Fish averaging 46.5 ± 0.65 g (mean ± SD) were fed one of the six experimental diets; one control (Cont), and five other diets were prepared by supplementing single-probiotics 1 ( Bacillus subtilis ; SP 1 , 2 × 10 9 CFU kg −1 diet), single-probiotics 2 ( Bacillus licheniformis ; SP 2 , 2 × 10 9 CFU kg −1 diet), multi-probiotics 1 ( Bacillus subtilis + Bacillus licheniformis ; MP 1 , 2 × 10 9 CFU kg −1 diet), multi-probiotics 2 (commercial probiotics; Bacillus subtills + Bacillus licheniformis + Paenibacillus polymyxa + Aspergillus oryzae + Saccharomyces cerevisiae ; MP 2 , 2 × 10 9 CFU kg −1 diet) and oxytetracycline (OTC) at 5 g OTC kg −1 diet. At the end of 8 weeks feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed SP 1 , MP 1 and MP 2 diets were significantly higher than those of fish fed control diet (P < 0.05). Superoxide dismutase (SOD) activity of fish fed MP 2 diet was significantly higher than those of fish fed OTC diet (P < 0.05). Nitro blue tetrazolium (NBT) activity and lysozyme activity of fish fed SP 1 , MP 1 and MP 2 diets were significantly higher than those of fish fed OTC diet (P < 0.05). However, there was no significant difference among fish fed SP 1 , SP 2 , MP 1 and MP 2 diets. During the Edwardsiella tarda challenge test, the first mortality occurred on day 2. After the 14 days challenge test, cumulative survival rate of fish fed MP 1 and MP 2 diets were significantly higher than those of fish fed control diet (P < 0.05). However, there was no significant difference among fish fed SP 1 , SP 2 , MP 1 , MP 2 and OTC diets in survival rate at the termination of the challenge test. Although there was little advantage in immunological parameters with fish fed MP diets, single and multi-probiotics were equally effective statistically. These results demonstrated that single or multi-probiotics had equal beneficial effect as an antibiotic replacer in terms of growth performance, non-specific immune responses and disease resistance in starry flounder. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the effects of different taurine levels on the conjugated bile acid composition and growth of juvenile rockfish. Five taurine level diets were made by the supplementation of taurine (0%, 0.5%, 1.0%, 1.5% and 2.0%) to a basal diet. Fish meal washed with 70% ethanol to exclude taurine was used for the sole protein source. Feeding experiments were accomplished at 15°C using juvenile fish (initial BW: 13.5 g). Fish were fed the experimental diets for 4 months. At the end of experiments, fish were weighed and stored at −80°C for analysis of free amino acids and conjugated bile acids contents. The growth performance and feed efficiency of Korean rockfish were improved by taurine supplementation in the experimental diets. The taurine contents of the whole body increased with the increase in the taurine supplementation. The primary conjugated bile acids in gall bladder were taurocholic acid (83.5-165.6 mg mL−1) and taurochenodeoxycholic acid (6.3-20.0 mg mL−1). Total bile acids increased with increases in dietary taurine. Taurocholic acid content was more than 95% of the total conjugated bile acids. This indicates that taurine is the sole amino acid to make conjugated bile acid in Korean rockfish. Dietary taurine levels improved the conjugated bile acid composition in juvenile Korean rockfish. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate dietary myo -inositol (MI) requirement of juvenile parrot fish. A basal experimental diet was formulated and used as a control and four other diets were prepared by supplementing 100, 200, 400 or 800 mg MI per kg − 1 diet (designated as M0, M100, M200, M400 and M800, respectively). Triplicate groups of fish (initial body weight, 11.5 ± 0.01 g) were fed one of the diets to apparent satiation twice daily for 18 weeks. The results showed the significant increase of growth performance at dietary MI level of 100 mg kg − 1 but no further improvement was observed at higher MI levels. Significantly lower feed conversion ratio was obtained in fish fed the M200 and M400 diets than those fed M0 diet. Significantly lower AST and ALT activities were recorded in fish fed 100 and 100–800 mg kg − 1 MI, respectively, compared to those fed the control. Whole-body protein content decreased significantly at all supplementation levels of MI in comparison to control. Liver MI concentration significantly increased by MI supplementation and inversely correlated with liver lipid content. Broken-line regression analysis indicated that MI requirement of parrot fish is 94.3 and 121.3 mg kg − 1 diet based on weight gain and liver MI concentration, respectively. The findings suggest that approximately 100 mg kg − 1 MI can support maximum growth of juvenile parrot fish and prevent a potential abnormal lipid metabolism. [ABSTRACT FROM AUTHOR]

Abstract: Two consecutive feeding trials were conducted to investigate taurine essentiality and requirement for parrot fish (Experiment I) and to determine whether taurine supplementation to high soybean meal (SM) diets would improve its growth performance (Experiment II). In Exp I, a fish meal (FM) based diet was used as a control and supplemented with 0.2, 0.4, 0.8, 1.2 or 1.6% taurine, and fed to triplicate groups of juvenile parrot fish (initial body weight, 13.5g) to apparent satiation for 8weeks. The growth and feed utilization were significantly improved by taurine supplementation up to 0.8% and thereafter plateaued. An optimum dietary taurine level was determined by a broken-line regression analysis based on weight gain and estimated at 0.88% diet. In Exp II, six experimental diets were prepared by supplementation of 0 or 1.0% taurine to a FM-based diet or addition of 0, 0.1% (low), 1.0% (medium) or 2.0% (high) taurine to a basal diet in which 30% of FM was replaced with SM (designated as FM, FM+T1, SM, SM+T0.1, SM+T1 and SM+T2, respectively). Each experimental diet was fed to juvenile parrot fish (initial body weight, 6.4g) twice daily to apparent satiation for 12weeks. The fish fed SM diet showed significantly lower growth performance compared to fish fed FM-based diets. Supplementation of taurine to SM diet significantly affected fish growth and higher performances were observed in fish fed SM+T1 or SM+T2 diets that were comparable to that of the fish fed FM diet. However, no significant changes were observed regarding the inclusion of taurine into FM-based diet. These results clearly demonstrated the positive effects of dietary taurine supplementation on feed utilization and growth performance of juvenile parrot fish when 30% FM was replaced with SM. The optimum dietary level of taurine seems to be approximately 1% in diets. [Copyright &y& Elsevier]

Abstract: Two studies were conducted to investigate the effects of dietary supplementation of three Bacillus spp. on growth performance, innate immunity and disease resistance of olive flounder against Streptococcus iniae and to examine the efficacy of Bacillus spp. on water quality reducing ammonia concentration and increasing fish survival. In the first experiment, a basal diet was prepared and regarded as a control and three other diets were prepared by supplementing one of three Bacillus spp. (B. subtilis, B. pumilus or B. licheniformis) at the dietary level of 0.5%. Triplicate groups of fish (initial body weight, 25g) were fed one of the four diets for eight weeks. Fish fed with B. subtilis containing diet showed significantly higher growth performance and feed efficiency than fish fed with the control diet. Also, significantly higher survival rates were observed in fish fed B. subtilis or B. pumilus containing diets during the feeding trial. Phagocytic activity was significantly increased in fish fed the probiotic containing diets and higher superoxide dismutase activity was observed in fish fed B. pumilus or B. licheniformis when compared to the control. However, serum lysozyme and myeloperoxidase activities did not significantly differ compared to the control. After a challenge with S. iniae, fish fed B. subtilis or B. licheniformis showed significantly higher survival rates compared to fish fed the control diet. In the second experiment, fish (30.1g) were fed a commercial diet for three weeks and then they were distributed to nine tanks at a density of 30 fish per tank (3 replicates per treatment). Fish were fasted for 5days in static water system, while one of two probiotics, B. subtilis or B. licheniformis was treated every 24h into the rearing water at the concentration of 104 CFUml−1. During the trial, significantly decreased ammonia concentration and fish mortality were observed by the supplementation of B. subtilis into the rearing water. The results in these studies indicate that B. subtilis has beneficial effects on growth performance, innate immunity and disease resistance of olive flounder and quality of the rearing water. [Copyright &y& Elsevier]

The effects of Bacillus sp. supplementation of different types of cells, such as spores and vegetative cells, on fish growth performance, intestinal microbial diversity alteration and immunity in juvenile olive flounder (Paralichthys olivaceus) were investigated. The fish were divided into three groups and provided with either a basal diet (control), Bacillus sp. vegetative cell (VCS) or spore (SS) supplemented diet for 8 weeks. At the end of the experiment, significant differences (P <.05) were found in terms of weight gain, specific growth rate, feed conversion ratio and protein efficiency ratio between the VCS and control groups. Respiratory burst, superoxide dismutase activity, and lysozyme activity, which are innate immune indicators, were observed with positive alterations (P <.05) in SS compared to controls. Intestinal microbial diversity analysis showed that the SS group had an increased richness estimate (Chao 1, ACE, and Jackknife) compared with the control group. Diversity estimates (Shannon and reverse Simpson) revealed that the VCS group was increased compared with the control group. Analyzing the similarity between groups through beta-diversity, Venn diagram, and heatmap analysis, the control and VCS groups were similar, and the SS group was different. IL-1β and TNF-α expression levels in the liver and spleen were increased in the SS group compared with the control group. In growth-related gene expression analysis, only growth hormone increased in the VCS group compared with the control group. In an in vivo challenge experiment with Streptococcus iniae (1 × 108 CFU/mL), the survival rates of the VCS and SS groups were 14.29% and 28.57%, respectively, when the control mortality reached 100%. Therefore, we concluded that supplementation of Bacillus sp. with different physiological processes affects the growth performance and immune activity of flounder. In particular, VCS can induce growth performance and growth-related gene expression, and SS can alter nonspecific immune and immune-related gene expressions. • The effect of dietary supplementation is affected by the Bacillus physiological process. • Dietary Bacillus vegetative cell supplementation improves growth performance. • Bacillus spore supplementation affects the intestinal microbial composition. • Nonspecific immunity is altered by Bacillus spore supplementation. • Pro-inflammatory cytokines are upregulated by dietary spore supplementation. [ABSTRACT FROM AUTHOR]

The overall performance and well-being of juvenile olive flounder were evaluated in response to three isonitrogenous and isolipidic extruded feed pellets containing either wheat flour (WF), potato (PS) or corn starch (CS), as a dietary carbohydrate source. Following the 2-week acclimation period, triplicate groups of fish (16.6 ± 0.01 g) were assigned to each experimental diet and fed to apparent satiation for 8 weeks. The results of the extruded feed pellet's physical quality tests revealed that dietary inclusion of PS could significantly enhance the water stability of the extruded feed pellets. In addition, PS and CS diets had significantly higher bulk density than WF diet. Feeding juvenile flounders with these experimental diets, however, did not induce any significant changes in their overall performance. Significantly higher serum lysozyme activity was recorded in fish fed the PS and CS diets than those fed the WF diet. Fish fed the WF and CS diets had significantly higher superoxide dismutase activity than PS group. Expression of the immune-related genes, including SOD2, EPX-L, TNF-L, IL-6, and TIPRL, was notably up-regulated in liver of fish fed the PS and CS diets compared to those fed the WF diet. Interestingly, however, an inverse expression pattern was found for the same genes in the spleen where lower expression levels were detected in the PS and CS groups than the WF group. Overall, our findings revealed that while dietary utilization of PS produced an extruded feed pellet with markedly higher physical quality than either WF or CS, neither of these starch sources were able to significantly impact the flounder's performance. Further studies are needed to elucidate the potential long-term consequences of the invoked immune response in the PS and CS groups. • Overall performance and well-being of juvenile olive flounders were evaluated in response to the extruded feed pellets containing either wheat flour, potato starch or corn starch as dietary starch sources. • Diets containing potato starch showed significantly higher water stability than the other two experimental diets. • Dietary inclusion of either potato or corn starch in the extruded diet significantly affected immune-related genes expression in the liver and spleen of flounders. • The expression patterns of the target genes involved in the immune response were opposite in the liver and spleen after feeding with different starch sources. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is known as a highly toxic heavy metal, and its toxicity varies depending on its form due to different toxicokinetics between inorganic and organic Hg. Limited information on comparison of Hg toxicity concerning its chemical form by oral exposure is currently available in cultured fishes. Therefore, we conducted a comparative study to have a better understanding of distinct toxic effects between mercuric chloride (HgCl 2) and methylmercury chloride (CH 3 HgCl) in Korean rockfish. The 12-weeks dietary exposure of HgCl 2 and CH 3 HgCl with its graded levels (0.4–6.4 ppm) (2 × 5 factorial design) in the young-of-the-year rockfish (initial weight: 82 ± 0.3 g) resulted in neither interactive nor main effects on whole-organism responses, including growth, feed utilization, and survival. However, the distinct pattern of Hg accumulation between the two forms in dorsal muscle, brain, liver and kidney tissues was observed, showing that the rockfish fed the CH 3 HgCl-contained diets exhibited the dose-dependent accumulation throughout the sampling points (1, 2, 4, 8, and 12 weeks post feeding), whereas those fed the HgCl 2 -contained diets did not show such response. The CH 3 HgCl exposure induced higher oxidative stress and immunotoxicity, reflected by the elevated plasma superoxide dismutase and lysozyme activities, respectively. In addition, the CH 3 HgCl-induced alteration in plasma measurements, including the plasma aspartate transaminase activity and total protein level was found. Taken together, the dietary exposure of methylmercury chloride had more pronounced toxic effects than mercuric chloride in the young-of-year rockfish, needed to be taken into consideration for regulation of maximum allowed levels for Hg by its chemical form. • Dietary-borne methylmercury chloride had higher toxicity than mercuric chloride. • Distinct toxicokinetics between the organic and inorganic mercury was found. • Immunotoxicity resulting from the methylmercury chloride exposure was detected. • Impaired liver function by the methylmercury chloride exposure was observed. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the effect of dietary differences on intestinal microbial population alteration and its relationship to immune-related gene expression in juvenile olive flounder (Paralichthys olivaceus). Initially, flounder were divided into three groups and supplemented with fishmeal diet (FM), fishmeal replaced by plant protein (termed low-fishmeal (LFM)), and Bacillus sp. SJ-10 probiotic-inoculated LFM (Pro) for 4 weeks. At the start (Initial group) and after completing the feeding trial, intestines were subjected to microbiota analysis and immune-related gene expression. The results of the intestinal microbiota analysis demonstrated that the FM and LFM groups' microbial richness (Chao1, ACE, and Jackknife) and diversity (Shannon and Simpson) did not differ significantly (P >.05) compared to the Initial group. However, the Pro group exhibited increased (P <.05) richness compared to all other groups, but its diversity was lower than that of the Initial group. A similar alteration phenomenon was also found in community composition between these two groups. At the phylum level, the most abundant phylum was Proteobacteria for all groups, but the second most abundant phylum in the Initial and Pro groups was Bacteroidetes, whereas in the FM and LFM groups, it was Firmicutes. An additional analysis of genus-level community composition and prediction of functional composition analysis showed differences among the groups. In the intestine, the transcription of interleukin (IL)-10 and IL-1β was increased more in the LFM and Pro groups compared to the FM group. IL-6 was increased only in the Pro group, and tumor necrosis factor-α (TNF-α) gene expression did not differ significantly among the groups. Therefore, we concluded that dietary changes affect intestinal microbiota composition and immune-related gene expression; in particular, diets containing probiotics can lead to greater change during the same feeding period. • Dietary changes affect intestinal microbiota composition and immune-related gene expression of olive flounder. • Probiotic have a greater impact on intestinal microbial diversity and composition than changes in fishmeal content. • Feed composition changes and probiotic supplements can manipulate the intestinal microbiota of olive flounder. [ABSTRACT FROM AUTHOR]

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. • Functional feed additives such as YEN, GAB, and SGS can enhance growth performance of olive flounder • YEN, GAB, and SGS improved intestinal villi length, trypsin activity, non-specific immune responses, and disease resistance • Selective functional feed additives (YEN, GAB, and SGS) can be considered cost-effective solutions in low fish meal diets [ABSTRACT FROM AUTHOR]