Dietary protein requirement of white sea bream (Diplodus sargus) juveniles

A trial was undertaken to estimate the protein requirement of white sea bream (Diplodus sargus). Five fish meal‐based diets were formulated to contain graded levels of protein (from 60 to 490 g kg^?1). Each diet was assigned to triplicate groups of 25 fish with a mean individual body weight of 22 g. Fish fed the 60 g kg^?1 protein diet lost weight during the trial, while growth improved in the other groups as dietary protein level increased up to 270–370 g kg^?1. Feed efficiency improved as dietary protein level increased. Maximum protein efficiency ratio (PER) was observed with the 17% protein diet. N retention (NR) (% N intake) was not different among groups fed diets with 17% protein and above. Ammonia excretion (g kg^?1ABW day^?1) increased as dietary protein level increased, while no differences in urea excretion were noted. An exponential model was used to adjust specific growth rate and NR (g kg^?1 day^?1) to dietary protein level. Based on that model, dietary protein required for maximum retention was 330 g kg^?1, while for maximum growth it was 270 g kg^?1. On a wet weight basis, there were no differences in whole body composition of fish‐fed diets with 170 g kg^?1 protein and above, except for the protein content, which was lower in group fed the 170 g kg^?1 protein diet than the 490 g kg^?1 protein diet. Specific activities of hepatic amino acid catabolism enzymes (glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase) increased as dietary protein levels increased. There were no differences among groups in fatty acid synthetase and malyc enzyme but 6‐phosphate dehydrogenase (G6PDH) was significantly lower in fish fed the 60 g kg^?1 protein diet than the 170 and 490 g kg^?1 protein diets.     

Effect of dietary protein and lipid levels on growth and feed utilization of white sea bream (Diplodus sargus) juveniles

In this study, two growth trials were conducted to evaluate the effect of dietary protein and lipid levels on growth and feed utilization of white sea bream (Diplodus sargus) juveniles. For the first trial, five diets were formulated to contain 120 g kg^?1 lipid and increasing levels of protein, ranging from 400 to 600 g kg^?1. Two additional diets were formulated with 400 and 600 g kg^?1 protein and 180 g kg^?1 lipids. The diets were fed to apparent visual satiety to duplicate groups of fish with a mean weight of 1.5 g for 10 weeks. For the second growth trial, four diets were formulated to contain 120 g kg^?1 lipid and 380–520 g kg^?1 protein. Two additional diets were formulated with 380 and 520 g kg^?1 protein and 180 g kg^?1 lipids. The diets were fed to apparent visual satiety to triplicate groups of fish with a mean weight of 41 g for 12 weeks. At the end of both trials, there were no growth differences among groups independent of the dietary protein content. In the first trial, growth was negatively correlated to dietary lipid levels. No significant differences of feed intake were detected among groups in both trials, but a direct correlation between feed efficiency and dietary protein level was observed. Protein efficiency ratio and nitrogen (N) retention (% N intake) significantly decreased with the increase of dietary protein levels. In both trials, energy retention (% energy intake) was highest in groups fed on diets with the highest protein‐to‐energy (P/E) ratio. At the end of both trials, no significant differences in whole‐body composition were observed among groups. Specific activity of enzymes involved in amino acid catabolism [aspartate aminotransferase (AST), alanine aminotransferase (ALT) and glutamate dehydrogenase (GDH)] showed no significant differences with dietary protein level in both trials. Nevertheless, in the first trial, a significantly lower GDH activity was observed in fish fed with higher dietary lipid levels. No differences were found for specific activity of the lipogenic enzymes, fatty aid synthetase and glucose‐6‐phosphate dehydrogenase, in the second trial. Results of this study indicate that a diet with a protein level of 380–420 g kg^?1 and a P/E ratio of 20 g protein MJ^?1 satisfies the growth requirements of D. sargus juveniles. Also, within the range tested, no evidence of protein sparing by dietary lipids seems to occur.     

Dietary supplementation of mannan oligosaccharide on white sea bream (Diplodus sargus L.) larvae: effects on development,gut morphology and salinity tolerance

The influence of dietary mannan oligosaccharide (MOS) on the development, gut integrity and quality (in respect of stamina and survivability) of white sea bream Diplodus sargus L. larvae was investigated. White sea bream larvae were held under appropriate rearing conditions and fed Artemia, enriched by A1 DHA Selco^? with the addition or absence of MOS (Bio‐Mos®). The results indicated that larval growth performance and survivability were not affected by the MOS supplementation. Light microscopy revealed that MOS supplementation significantly improved the intestinal morphology by increasing the villi surface area by over 12%. Transmission electron microscopy revealed that MOS supplementation increased the microvilli length by 26% compared with the control. Salinity challenge experiments showed that MOS significantly increased larval stamina and survival in both 0 and 60 mg L^?1 salinity water by 13% and 22.9% respectively. These improvements in the larval quality at the early stages of fish development are important for the efficiency of intensive hatchery production.     

Dietary supplementation of β‐glucan improves growth performance,the innate immune response and stress resistance of red sea bream,Pagrus major

A 56‐day feeding trial was conducted to evaluate the effects of supplemented diets with β‐glucan (BG) at four levels [0 (D1), 250 (D2), 500 (D3) and 1000 (D4) mg BG kg^?1] on red sea bream, Pagrus major. The obtained results revealed a significant increase (P < 0.05) in final body weight, weight gain, specific growth rate, feed intake, body protein content, lysozyme activity and tolerance against low‐salinity stress test in all BG‐supplemented groups when compared with BG‐free group. Furthermore, D4 group resulted in a significant increase in feed efficiency ratio, protein gain, protein and lipid digestibilities, serum bactericidal activity and peroxidase content when compared with D1 group (P < 0.05). Haematocrit and plasma protein content in D3 group were significantly higher than those in D1 group (P < 0.05). Interestingly, BG supplementation decreased glutamic oxaloacetic transaminase (GOT) in D2 group and reactive oxygen metabolites in D2, D3 and D4 groups when compared with D1 group. Following low‐salinity stress test, significantly higher amounts of secreted mucus were observed in fish fed D2 and D4 diets than those from fish fed D1 diet (P < 0.05). In conclusion, the supplementation of BG improves growth, stress resistance and immune response of P. major.     

Effect of different feeding strategies on gilthead sea bream (Sparus aurata) demand-feeding behaviour and nutritional utilization of the diet

We have studied the effects of time‐restricted food access and ration restriction on gilthead sea bream demand‐feeding behaviour and nutritional use of the diet (Sparus aurata), and also compared the nutritional efficiency of three different feeding systems: manual, automatic and modulated‐automatic. In the first trial, fish were allowed to feed from self‐feeders under three different conditions: ad libitum, ration restriction, and time‐restricted food access, and their demand‐feeding pattern, diet utilization and body composition were analysed. In the second trial, animals were fed by hand or using an automatic system, either fixed or modulated, and diet utilization and body composition were analysed as before. Restricting the amount of food modifies gilthead seabream self‐feeding behaviour, with fish increasing the number of demands provided these are rewarded with food. However, demand‐feeding activity does not increase if rewards are restricted to a certain time. Feeding gilthead sea bream by hand versus automatically, and distributing the daily food ration in two or three equal or unequal‐size daily meals, have no effect on the animals’ growth, nutritional use of the diet or body composition.     

Effect of dietary starch source (normal versus waxy) and protein levels on the performance of white sea bream Diplodus sargus (Linnaeus) juveniles

An experiment was performed to evaluate the growth performance and feed utilization of white sea bream juveniles (initial weight, 14 g) fed diets of cornstarch of different origins (normal and waxy). Four experimental diets were formulated to be isolipidic and to contain normal and waxy starch (26% or 42%) at two protein (36% and 48%) levels. The growth trial lasted 15 weeks and, at the end of the trial, there were no differences in the growth rate among groups. At the highest dietary starch level – but not at the lowest level – the feed efficiency ratio and PER were significantly lower in fish fed the waxy starch diet. Protein efficiency ratio and N retention (% N intake) were not affected by starch source but were significantly higher in the diets with a lower protein content. No differences in energy retention (% energy intake) were observed among groups. Except for the protein content, which was significantly higher in fish fed diets with a high protein level, no other differences were observed among groups in whole‐body composition. Hepatosomatic Index (HSI) was significantly higher in fish fed high‐starch diets, but there were no differences in visceral indices among groups. The apparent digestibility coefficients of protein and energy were not affected by the dietary starch level, but were significantly lower in diets including waxy starch. Glutamate dehydrogenase activity was higher in fish fed high‐protein diets, but it was not affected by dietary starch source. Alanine aminotransferase and aspartate aminotransferase activities were not different among groups. Glucose 6‐phosphate dehydrogenase, malic enzyme and fatty acid synthetase activities were not affected by the dietary starch level, but were significantly lower in fish fed waxy starch. The results of this study indicate that diets for white sea bream juveniles may include up to 42% starch without negative effects on fish performance. Moreover, normal starch appears to be more efficiently used as an energy source than waxy starch.     

Biomarkers of bone development and oxidative stress in gilthead sea bream larvae fed microdiets with several levels of polar lipids and α‐tocopherol

Although dietary marine phospholipids are able to improve culture performance of marine fish larvae in a further extend than soybean lecithin, both types of phospholipids (PL) markedly increase oxidative risk. The inclusion of a fat‐soluble antioxidant such as the vitamin E α‐tocopherol could allow a better control of oxidative stress. The objective of this study was to determine the combined effect of graded levels of α‐tocopherol with different levels and sources of krill phospholipids (KPL) and soybean lecithin (SBL) on growth, survival, resistance to stress, oxidative status, bone metabolism‐related genes expression and biochemical composition of sea bream larvae. Sea bream larvae were completely weaned at 16 dph and fed for 30 days seven microdiets with three different levels of PL (0, 40 and 80 g kg^?1 diet) and two of α‐tocopherol 1500 and 3000 mg kg^?1 diet. Sea bream larvae fed diets without PL supplementation showed the lowest survival, growth and stress resistance, whereas increase in PL, particularly KPL, markedly promoted larval survival and growth. However, feeding SBL markedly increased TBARs and GPX gene expression increasing the peroxidation risk in the larvae. Besides, KPL inclusion improved incorporation of n‐3 HUFA and, particularly, EPA into larval tissues, these fatty acids being positively correlated with the expression of BMP‐4, RUNX 2, ALP, OC and OP genes and to bone mineralization for a given larval size class. The increase in dietary α‐tocopherol tends to improve growth in relation to the n‐3 HUFA levels in the diet, denoting the protective role of this vitamin against oxidation. Indeed, dietary α‐tocopherol decreased the oxidative stress in the larvae as denoted by the reduction in larval TBARs contents and gene expression of SOD and CAT, but not GPX. Thus, increase in dietary α‐tocopherol effectively prevented the formation of free radicals from HUFA, particularly EPA, but did not affect the incidence of bone anomalies or the expression of genes related to osteogenetic processes.     

Prebiotics effect on growth performance,hepatic intermediary metabolism,gut microbiota and digestive enzymes of white sea bream (Diplodus sargus)

This study aimed at evaluating the effects of short‐chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS) and galactooligosaccharides (GOS) on growth performance, hepatic metabolism, gut microbiota and digestive enzymes activities of white sea bream juveniles. Four diets were formulated: a control diet with fish meal (FM) and plant feedstuffs (PF) (30FM:70PF) and three test diets similar to control but supplemented with 10 g of scFOS, XOS or GOS per kilo diet, which were fed to fish during 12 weeks. Prebiotics had no effect on growth, feed efficiency or gut microbiota. Plasmatic triglycerides were lower in fish fed XOS than FOS and GOS diets. Malic enzyme activity was lower in fish fed XOS than FOS diet. Fish fed XOS diet had lower fatty acid synthetase (FAS), a key lipogenic enzyme and higher alanine aminotransferase activities. Fifteen days after the start of the trial, an enhancement of total alkaline protease, trypsin and lipase activities was observed in fish fed prebiotics, but such effect disappeared at 12 weeks. In conclusion, scFOS, XOS or GOS seem to have limited applicability in white sea bream feed.     

Feed intake,growth, feed utilization,body composition and waste output of juvenile hybrid bream at different feeding frequencies

An eight‐week feeding trial was conducted to evaluate the feed intake, growth, feed utilization, body composition and waste output of juvenile hybrid bream at different feeding frequencies (0.5, 1, 2, 3 or 4 meals/day). Fish (initial body weight of 10.6 ± 0.8 g) were fed to satiation at each feeding. The test diet contained 336 g/kg crude protein and 79 g/kg crude lipid. The weight gain significantly increased with increase in feeding frequency from 0.5 to 3 meals/day (p < 0.05) and afterwards did not change with feeding frequency from 3 to 4 meals/day (p > 0.05). The feed intake increased with increase in feeding frequency (p < 0.05). Fish fed at 3 meals/day exhibited the lowest feed conversion ratio and waste output of nitrogen and phosphorus, however, the highest nitrogen retention efficiency (p < 0.05). No significant differences were found in the phosphorus retention efficiency, the body composition of crude protein, ash and phosphorus among all the feeding frequencies (p > 0.05). The body lipid content increased, whereas the content of moisture decreased, with the increase in feeding frequency (p < 0.05). The present study reveals that the optimum feeding frequency is 3 meals/day for hybrid bream.     

Utilization of dietary starch and glucose tolerance in juvenile chinook salmon (Oncorhynchus tshawytscha) of different strains in seawater

Juvenile chinook salmon of three strains responded to inclusion of 28.7% of gelatinized starch in the diet with different degrees of reduction in growth rate and feed efficiency relative to control fish of the respective strains fed a low-starch, high-lipid diet of similar protein (46%) and estimated metabolizable energy content (16 mJ/kg). The productive protein value of the diet was not reduced to the same extent by the high intake of starch. Carcasses of fish fed the high-starch diet contained higher concentrations of protein and lower concentrations of lipid than control fish. The accumulation of liver glycogen in response to the high-starch diet differed among strains. Glucose tolerance curves also varied among strains but were poorly correlated with plasma concentrations of insulin. Tolerance to glucose loading was improved in fish previously fed the high-starch diet.     

Effects of partial substitution of dietary fish meal by fermented soybean meal on growth performance,amino acid and biochemical parameters of juvenile black sea bream Acanthopagrus schlegeli

A feeding trial was conducted to evaluate the effect of replacing fish meal protein with fermented soybean meal (FSM) on the growth performance, feed utilization, amino acid profile, body composition, morphological parameters, activity of antioxidant and digestive enzymes of black sea bream (Acanthopagrus schlegeli) juvenile. Five isonitrogenic and isolipidic diets were prepared with levels of 0 (control), 80, 160, 240 and 320 g kg^?1 FSM. Triplicate groups (40 fish per tank) of juvenile black sea bream with initial weight of 1.17 ± 0.04 g were hand‐fed to visual satiation at three meals per day for 8 weeks. The fish fed diets containing different levels of FSM had no significant differences regarding survival and specific growth rate compared with control group. Feed and protein efficiency ratios of fish fed diet containing 320 g kg^?1 FSM were significantly lower than those of control group. Daily feed intake and daily protein intake of fish fed diet containing 240–320 g kg^?1 were significantly higher than those of control group. Hepatosomatic index and condition factor of fish were not affected by different dietary FSM level. Fish fed diets containing 240–320 g kg^?1 FSM had significantly higher visceral somatic index than control group. Whole body proximate and amino acid compositions of fish were not affected by dietary FSM level. The activity of digestive enzymes in the intestine was not affected by dietary FSM level. The activity of glutathione peroxidase in liver was significantly higher for fish fed the diet containing 160 g kg^?1 FSM compared with control group. This study showed that up to 40% fish meal in the diets of juvenile black sea bream could be replaced by fermented soybean meal with supplementation of methionine, lysine and taurine.     

Growth performance and metabolic utilization of diets with native and waxy maize starch by gilthead sea bream (Sparus aurata) juveniles

The effect of dietary starch source and level on growth performance, feed utilization, apparent digestibility coefficients and liver enzyme activities involved in intermediary metabolism of gilthead sea bream juveniles was studied. Five isonitrogenous (47% crude protein) and isolipidic (15% crude lipids) diets were formulated to contain 10% native (diet NS10) or waxy (diet WS10) maize starch; 20% native (diet NS20) or waxy (diet WS20) maize starch or no starch (control). Diets were adjusted with α-cellulose. Another diet was formulated without carbohydrates, and contained 70% crude protein and 15% crude lipids (diet HP). Each diet was fed to triplicate groups of 30 fish (initial weight: 20 g) for 12 weeks. The HP group was fed to near satiation and the other 5 groups were fed on a pair-feeding scheme according to the group that ingested less feed (control diet group). The reduction of dietary protein level from 70% to 47% by the incorporation of 20% starch did not significantly affect gilthead sea bream growth performance or feed efficiency. Compared to the control diet, neither the level nor the nature of starch had any measurable effect on growth performance and feed efficiency. Digestibility of starch was unaffected by source or dietary inclusion level. Diet had no effect on plasma glucose levels, but liver glycogen was higher in diet groups NS20, WS20 and HP. Dietary carbohydrates increased GK and G6PD enzyme activities and decreased ALAT and GDH enzyme activities while had only a minor effect on FBPase activity. The nature of dietary starch tested (native or waxy) had little influence on performance criteria.     

High dietary starch impaired growth performance,liver histology and hepatic glucose metabolism of juvenile largemouth bass,Micropterus salmoides

A 60‐day experiment was carried out to investigate dietary starch levels on growth performance, hepatic glucose metabolism and liver histology of largemouth bass, Micropterus salmoides. Fish (initial weight 22.00 ± 0.02 g) were fed five graded levels of dietary corn starch (0, 50, 100, 150 and 200 g/kg). Fish fed low (0 and 50 g/kg) dietary starch showed significantly higher weight gain than other groups (p < .05). Liver lipid and glycogen accumulations were induced when dietary starch higher than 100 g/kg. After 20 days of feeding, hexokinase activity and mRNA expression were decreased in fish fed dietary starch higher than 150 g/kg (p < .05) and the pyruvate kinase showed the opposite tendency. Insulin receptor 1 (irs1), glucagon‐like peptide‐1 receptor and glucose transport protein 2 (glut2) mRNA expression were decreased with the increasing dietary starch after 10 days of feeding (p < .05). These results indicated gluconeogenesis was depressed and β‐oxidation was enhanced in response to high dietary starch, while the glycolysis was inhibited and endocrine system was impaired when fish fed high dietary starch; then, glucose homeostasis was disturbed and finally led to the glucose intolerance of largemouth bass.     

Effect of dietary supplemental l‐carnitine on growth performance,body composition and antioxidant status in juvenile black sea bream,Sparus macrocephalus

Effects of dietary l ‐carnitine were studied in juvenile black sea bream (Sparus macrocephalus). The semipurified basal diet [crude protein 450 g kg^?1 dry matter (DM); crude lipid 126 g kg^?1 DM] was formulated to choose white fishmeal as the protein source and fish oil plus corn oil (1 : 1) as the lipid source. Six diets (control + diets 1–5) containing 0.1, 0.12, 0.16, 0.24, 0.39 and 1.1 g of l ‐carnitine kg^?1 diet were fed to triplicate groups of black sea bream (initial weight 13.10 ± 0.05 g) for 8 weeks. At the end of the feeding trial, growth performance, body composition and antioxidant status were determined. The results showed that relative growth rate (RGR) was significantly improved by the elevation of dietary l ‐carnitine level from 0.1 to 0.24 g kg^?1, but decreased with further increment (P < 0.05). Lipid content decreased significantly (P < 0.05) in the dorsal muscle whereas increased (P < 0.05) in the liver with the addition of dietary l ‐carnitine. Dietary l ‐carnitine supplements elevated enzymatic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione‐S‐transferase, GST) activities (P < 0.05) yet decreased the content of non‐enzymatic factor, total sulphydryl groups (TSH) (P < 0.05). In summary, the optimum dietary l ‐carnitine level was 0.284 g kg^?1 diet by second‐polynomial regression analysis based on RGR (y = ?647.4x² +367.97x + 234.55; R² = 0.977, x = dietary l ‐carnitine levels, y = RGR), and dietary l ‐carnitine addition within the levels adopted in our study could depress lipid peroxidation in tissues of juvenile black sea bream.     

Effects of dietary starch levels on the growth,plasma metabolites and expression of genes involved in glucose transport and metabolism in Pelodiscus sinensis juveniles

A 10‐week feeding trial was conducted to evaluate the growth performance, glucose transport and metabolism of Chinese soft‐shelled turtles (Pelodiscus sinensis) exposure to graded levels of dietary starch (0.52%, 7.43%, 14.74%, 22.99% and 31.38%). The 360 turtles (initial body weight, 12.94 ± 0.50 g) with 12 replicates were randomly assigned to five experimental diets. The highest weight gain and specific growth rate (SGR) were observed in 7.43% group and the lowest in 31.38% group. The protein efficiency ratio, whole‐body lipid contents, hepatic glycogen contents and the 4‐hr postprandial plasma glucose levels were significantly increased with the increment of starch levels (p < .05). In contrast, the daily feed intake and feed conversion ration were significantly declined (p < .05). The mRNA levels of glucose transporter 2, glucokinase, pyruvate kinase, malic enzyme and acetyl‐CoA carboxylase alpha genes in the liver significantly increased as the increase in starch levels at 4‐hr and 24‐hr post feeding (p < .05). No significant differences were observed in the expression of gluconeogenesis genes at each time point (p > .05). These results suggested that dietary addition of starch up‐regulated hepatic glycolysis, glycogenesis and lipogenesis genes expression, but the deficient response of gluconeogenesis to dietary starch might be part of the causes limited the starch utilization. Based on the secondary polynomial regression of SGR, y = ?0.0011x² + 0.028x + 1.63 (R² = 0.9292), the 12.73% inclusion level of dietary starch was recommended in juvenile turtles.     

Histological alterations in the liver of sea bream, Sparus aurata L., caused by short- or long-term feeding with vegetable oils. Recovery of normal morphology after feeding fish oil as the sole lipid source

This study evaluated the effects of fish oil (FO) replacement by vegetable oils [soybean oil (SO), rapeseed oil (RO), linseed oil (LO)] and subsequent feeding with FO on the liver morphology of sea bream. A short-term trial (3 months) and long-term trial (6 months) were carried out feeding sea bream with the following experimental diets: FO100%; SO60% + FO40%; RO60% +FO40%; LO60% + FO40%; SO + RO +LO60% + FO40%. Finally, all groups from the long-term trial were fed with FO100% for 95 days (washout period). Liver samples were taken for histological and biochemical studies. In both the short- and long-term trials, livers of sea bream fed LO60% and SO + RO + LO60% showed a similar hepatic morphology to that observed in fish fed FO100%. In contrast, sea bream fed SO60% showed an intense steatosis, with foci of swollen hepatocytes containing numerous lipid vacuoles. After the washout period, a considerable reduction of the cytoplasmic vacuolation and the lipid vacuole accumulation were observed in the livers of fish fed the different experimental diets. The results of this study suggested that the type of non-essential fatty acid, characteristic of vegetable oils, induces the appearance of steatosis in the following order: linoleic acid > linolenic acid > oleic acid. However, the liver alterations found during the experimental periods with vegetable oils are reversible when the fish are re-fed with a balanced diet (FO100%), indicating the non-pathological character of these histological changes.     

Utilization of dietary carbohydrates by sea cucumber Apostichopus japonicus (Selenka) as indicated by carbon stable isotope analysis

Carbon stable isotopes were used as trophic markers to investigate the utilization of dietary terrestrial‐source carbohydrates by sea cucumber Apostichopus japonicus. Sea cucumbers were fed by five different types of diets with the ingredients containing Sargassum muticum either without starch or with one of the four starches including corn starch, sweet potato starch, tapioca starch and potato starch. After the 70‐day feeding trial, the carbon isotopic compositions of A. japonicus appeared to reflect those of corresponding dietary components. The average contribution of corn starch (22.0%) to the growth of A. japonicus was slightly higher than the expected contribution (20%). While the proportional contributions of sweet potato, tapioca and potato starches (6.0%, 7.0% and 4.0%, respectively) were all considerably lower relative to the expected contributions. These results indicated that A. japonicus could utilize corn starch more efficiently than sweet potato, tapioca or potato starch. Moreover, A. japonicus fed diet containing corn starch showed the highest specific growth rates which were significantly higher than those fed diets containing potato or tapioca starch. The results of the present study suggested that the corn starch could be used as dietary carbohydrate source in the artificial feeds for A. japonicus farming.     

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

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

Effect of dietary saturated and monounsaturated fatty acids in juvenile barramundi Lates calcarifer

Barramundi (Lates calcarifer), a catadromous teleost of commercial interest, perform well when fed a wide range of dietary oils. However, the range of alternative oils now being explored is typically rich in saturated and monounsaturated fatty acids (SFA and MUFA). In this study, the response of juvenile barramundi (47.0 g per fish initial weight) fed isolipidic and isoenergetic diets with 82 g kg^?1 added oil was tested. The experimental test diets had a 2 : 1 or 1 : 2 ratio of SFA to MUFA (SFA‐D and MUFA‐D, respectively) compared to a control diet (CTRL‐D) fed for 8 weeks. The diets containing mostly olive oil (dietary MUFA‐D) and mostly refined palm oil (dietary SFA‐D) did not impact the growth performance or feed utilization parameters of the barramundi. The in vivo beta‐oxidation activity was consistent with the dietary fatty acid composition, with the most dominant FA being heavily beta‐oxidized. Together, the in vivo whole‐body mass balance of fatty acids showed that n‐3 long‐chain polyunsaturated fatty acids (LC‐PUFA) were most efficiently utilized in the SFA‐D‐ and MUFA‐D‐fed fish. This study provides evidence that additional dietary MUFA and SFA are suitable lipid classes for juvenile barramundi and they are both equally efficient at sparing LC‐PUFA from an oxidative fate.     

Effects of dietary supplementation of A3α‐peptidoglycan on the growth,immune response and defence of sea cucumber Apostichopus japonicus

To determine the effects of A3α‐peptidoglycan (A3α‐PG) extracted from Bifidobacterium sp. on the growth, immune response and disease resistance of sea cucumber Apostichopus japonicus, a 70‐day feeding trial was conducted in this study. A total of 216 sea cucumbers were fed with four practical diets prepared from a commercial feed with different contents (0, 1.5, 2.5 and 4.0 g kg^?1) of A3α‐PG. The specific growth rate (SGR), total coelomocyte count (TCC), phagocytotic activity and activities of four immunological enzymes in both cell‐free coelomic fluid (extracellular, EC) and coelomocyte lysate supernatant (intracellular, IC), including acid phosphatase (ACP), alkaline phosphatase (ALP), peroxidase (POD) and superoxide dismutase (SOD), were measured at the end of the feeding trial. Finally, the animals were administered a 16‐day Vibrio splendidus challenge via intraperitoneal injection to test the potency of A3α‐PG on disease resistance. Compared with the control (0 g kg^?1 A3α‐PG), a significant increase (P < 0.05) in SGR was observed in the groups fed with 1.5 and 2.5 g kg^?1 A3a‐PG. The TCC, ranging from 7.25 × 10⁶ to 1.05 × 10⁷ cells mL^?1, was not significantly affected (P > 0.05) by A3α‐PG,. Coelomocyte phagocytotic activities in all of the A3α‐PG‐supplemented groups were significantly activated (P < 0.05), but no significant difference (P > 0.05) was observed. Sea cucumbers fed with 1.5 and 2.5 g kg^?1 A3α‐PG exhibited significant activation (P < 0.05) of EC/IC‐ACP, EC/IC‐ALP, and EC/IC‐POD activities. A significant increase in EC‐SOD activities (P < 0.05) was exhibited by all groups with A3α‐PG supplementation. The challenge test showed that animals fed with diets containing 2.5 and 4.0 g kg^?1 A3α‐PG had significantly lower cumulative mortalities compared with the control 16 days after exposure. All of the results presented here show that A3α‐PG can positively enhance the growth, immune response and disease resistance of sea cucumber, suggesting that dietary supplementation of A3α‐PG has potential applications in the health management of economic species of sea cucumber.