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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]

This study analyzed the expression of growth‐related genes of olive flounder, Paralichthys olivaceus, fed a low‐fish meal (FM) diet to investigate the replacement of the FM diet in the field. The expression of growth hormone (GH)/insulin‐like growth factor (IGF) axis genes in the brain/pituitary/liver and plasma hormone concentrations were measured. A basal experimental diet was formulated using 63% FM and 12% soybean meal as the primary protein sources, and then two other diets were made by replacing 20% and 30% of the FM with soy protein concentrate, tankage meal, and poultry by‐products meal. Each diet was fed to duplicate groups of juvenile flounder (150 ± 3.0 g) twice a day. After 20 weeks, the plasma growth‐related hormone concentrations were similar between the control and FM20 groups. Moreover, GH/IGF axis gene mRNA expression in the brain/pituitary/liver was similar between the control and FM20 groups. Immunoblotting of muscle and liver showed the same pattern. This study showed the utility of replacing 20% of the FM diet and supports the possibility of field application. [ABSTRACT FROM AUTHOR]

Simple Summary: The demand for fishmeal is increasing due to aquaculture development, but the supply is unstable. This indicates the need to reduce the fishmeal content in the feed and develop an optimal fish-feed formulation through substitutes. However, most studies on reducing fishmeal content in feed were conducted at the laboratory level. In this study, the application of a low-fishmeal diet as feed to olive flounder was evaluated in terms of growth-related factors, digestive physiology, and microbiota raised for five months in a fish farm using four feed formulations- FM70 [control (CON), 70% fishmeal], FM45 (45% fishmeal), FM35A (35% fishmeal), and FM35B (35% fishmeal + insect meal). There was no difference in growth-related factors, digestive physiology, and gut microbiota diversity compared with the CON-fed fish. Therefore, reducing the fishmeal content of the feed by up to 35% does not adversely affect growth and physiological characteristics under farm conditions. In olive flounder (Paralichthys olivaceus), growth performance, expression of growth-related factors, digestive physiology, and gut microbiota were assessed under farm conditions in the fish fed diets with low levels of fishmeal. Four experimental diets were prepared, FM70 [control (CON), 70% fishmeal], FM45 (45% fishmeal), FM35A (35% fishmeal), and FM35B (35% fishmeal + insect meal), and fed to the fish for five months. The CON-fed fish had the highest plasma GH, but IGF-1 and hepatic IGF-1 mRNA expression of the olive flounder fed diets with low-fishmeal levels did not significantly differ among diets. The intestinal villus length, muscular thickness, and the number of goblet cells were statistically similar, and ocular examination of hepatopancreas showed no discernable difference in all experimental diets. The chymotrypsin content of FM35B-fed fish is significantly lower, but trypsin and lipase contents are similar. The diversity of gut microbiota did not differ among groups, although the FM35B group had a higher composition of Firmicutes. Thus, a diet with reduced fishmeal content and several alternative protein sources can be used as feed ingredients in feed formulation for olive flounder reared under typical aquaculture farm conditions. [ABSTRACT FROM AUTHOR]

Suitability of various animal by‐product meals was evaluated as an alternative source for fish meal (FM) in olive flounder feed when 30% FM was substituted. Juvenile fish (n = 480) was distributed into 24 flow‐through tanks. Seven experimental diets were prepared. 65% FM and 12% soybean meal were included as the protein source in the control (Con) diet. Thirty per cent of FM was substituted with tuna by‐product, chicken by‐product, hydrolysed chicken offal, meat, meat and bone, and blood meals, referred to as the TBM, CBM, HCOM, MM, MBM and BM diets respectively. Each diet was hand‐fed to satiation for 8 weeks. Weight gain, specific growth rate (SGR) and feed efficiency ratio (FER) of fish fed the TBM diet were greater than those of fish fed all other diets. Weight gain, SGR and FER of fish fed the Con diet was also greater than those of fish fed the MM and BM diets. The proximate composition of the whole body fish was unaffected by the experimental diets. Lysozyme activity of fish fed the Con, TBM and CBM diets was higher than that of fish fed the MM and BM diets. Amino acid profiles of fish were not affected by the experimental diets except for tryptophan. All fatty acid profiles of fish except for eicosadienoic acid were affected by the experimental diets. In conclusion, tuna by‐product and chicken by‐product meals are the good substitutes for FM in olive flounder feed when 30% of FM at 65% in diet was replaced with animal by‐product meals. [ABSTRACT FROM AUTHOR]

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]

A 12‐week feeding trial was designed to assess the probiotic potential of indigenous Bacillus amyloliquefaciens and/or Bacillus subtilis singly or in combination with Bacillus licheniformis in an extruded feed for olive flounder (Paralichthys olivaceus) juveniles. A high fish meal (FM) diet (control) and a low‐FM diet containing an alternative protein blend (30% FM replacement, FM30) were formulated. Three other experimental diets were prepared by inclusion of B. amyloliquefaciens (BA), B. subtilis (BS), or a mixture of B. amyloliquefaciens, B. subtilis, and B. licheniformis (BASL) into FM30 diet, with a final concentration of 106 CFU/g diet. Results indicated that the FM30 diet was well tolerated by flounder, and the overall performance was not affected by dietary treatments. Lysozyme activity and total immunoglobulin level were significantly reduced in flounders when fed with the FM30 diet compared with the BASL and BA diets, respectively. The Bacillus additives neither enriched the relative abundance of the corresponding Bacillus spp. in the relevant gut microbiota of olive flounder nor modulated the presumptive gene functions of the gut microbiome. Despite the absence of growth‐promoting effect, the tested probiotics could still be economically viable for use as immunostimulants in commercial flounder diets with partial FM replacement. [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]

Simple Summary: Increasing demand for an efficient and economic fishmeal feed for sustainable aquaculture has urged the aquafeed sector to seek an optimum fish-feed formulation. This study investigated the physiological response in olive flounder fed various fishmeal diets in a typical fish farm. The fish were farmed for 20 weeks, using the following experimental feeds: a control feed (CON), a replacement by 20% (F20), and 30% (F30) of the fish meal content of the CON. All groups showed no significant difference in growth and survival rates. However, due to investigating hormone expression associated with maturation, high expression of PSS-I and low expression of FSH-β, ER-α, and ER-β in FM30 compared to other experimental groups were observed. Therefore, up to 30% fishmeal replacement does not affect growth, but it appears to have a slight effect on the sexual development of olive flounder. Olive flounder (Paralichthys olivaceus) is a commercially important and valuable species for aquaculture in Korea. Due to the unstable supply of fishmeal for farmed fish, an optimum fish-feed formulation should be researched to ensure the sustainability of P. olivaceus aquaculture. This study investigated the effect of three experimental diets: Con (basal diet); FM20 (20% fishmeal replacement of CON); and FM30 (30% fishmeal replacement of CON) on P. olivaceus over 20 weeks at a typical farm by monitoring the growth and factors relating to sexual maturation. The results showed that no differences in growth were observed between the CON and diet-replacement groups. Gonadal oocyte development was similar between the CON and diet-replacement groups. Moreover, sbGnRH and GH expression did not differ between the CON and diet-replacement groups. The levels of Erβ and Vtg expression were significantly higher in the FM20 group than in the CON and FM30 groups after the experimental period. The expression of PSS-I was significantly higher in the FM30 group than in the CON and FM20 groups. Therefore, although growth occurred when 30% of the fishmeal was replaced, such high dietary protein replacement may be ill-advised during the maturation of olive flounder at the commercial fish farm. [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]