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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]

A 20‐week feeding trial was performed to evaluate the optimum level of animal and plant protein sources as substitutes of fishmeal (FM) in the diets of sub‐adult olive flounder (Paralichthys olivaceus) under farmed conditions. Groups of ninety fish averaging 478 ± 4.7 g (mean ± SD) were randomly distributed into four treatments in triplicates. An FM‐based diet was used as control (CON) and three other diets replaced 20% (APP20), 30% (APP30) and 40% (APP40) of FM with animal (tankage meal and poultry by‐product meal) and plant (soy protein concentrate) protein sources. Weight gain, specific growth rate and protein efficiency ratio were not significantly different among fish fed all the experimental diets (p > 0.05). The feed efficiency of fish fed the APP40 diet was significantly lower than those of fish fed the other experimental diets (p < 0.05). Non‐specific immune responses such as superoxide dismutase activity and lysozyme activity of fish fed all the experimental diets were not significantly different (p > 0.05). Intestinal villi length of fish fed the CON diet was significantly higher than those of fish fed the other diets (p < 0.05). Based on the results of growth performances and the non‐specific immune responses, the dietary combination of animal and plant protein sources could replace up to 40% of FM in sub‐adult olive flounder. [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]

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]