Stimulatory effect of dietary taurine on growth performance,digestive enzymes activity,antioxidant capacity,and tolerance of common carp, <Emphasis Type="Italic">Cyprinus carpio</Emphasis> L., fry to salinity stress

The present study was carried out to evaluate the effect of dietary taurine (Tau) on performance, digestive enzymes, antioxidant activity, and resistance of common carp, Cyprinus carpio L., fry to salinity stress. Fish (0.97?±?0.033 g) were fed on different taurine levels of 0.0 (control), 5, 10, 15, or 20 g/kg diet up to satiation twice daily for 8 weeks. At the end of the feeding trial, fish were stressed by exposure to 10 ppt salinity for 3 days during which fish mortality was observed. Fish performance was significantly (P?<?0.05) improved by dietary taurine up to 15 g Tau/kg diet after which fish growth and feed intake were almost the same. Also, taurine supplementation significantly (P?<?0.05) elevated activities of intestinal amylase, lipase, and protease resulting in an improving in feed intake giving better performance. Furthermore, Tau-stimulated antioxidant activity of common carp was observed in a dose-related manner, where activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly (P?<?0.05) higher, but malondialdehyde (MDA) value was significantly (P?<?0.05) lower in Tau-fed fish groups than those fed the control diet. In salinity stress experiment, highest survival rate was observed at fish fed Tau-supplemented diets without significant (P?>?0.05) differences over fish fed the control diet. It appears that taurine could be used as a feed supplement to confer better growth and health of common carp fry with optimal level of 15 g/kg diet.     

Enhancing the dietary value of palm oil in the presence of lysolecithin in tiger shrimp, <Emphasis Type="Italic">Penaeus monodon</Emphasis>

The effect of four iso-nitrogenous and iso-lipidic diets containing soy lecithin and lysolecithin with fish oil (sardine) and palm oil on growth, digestibility, and fatty acid composition of tail muscle and non-muscle portions of tiger shrimp, Penaeus monodon, was evaluated. Shrimp fed with lysolecithin diets had significantly (P?<?0.05) higher daily growth coefficient values (1.40–1.45% day^?1) than those fed with soylecithin containing diets (1.32–1.37% day^?1). Correspondingly, lysolecithin-supplemented diets showed significantly higher (P?<?0.05) apparent digestibility coefficients (ADC) of fatty acids with both the oils due to higher emulsification ability of small micelle forming by lysolecithin. However, there were no significant differences in survival and FCR among all treatments. The fatty acid composition of the test diets reflected to a certain extent in the fatty acid composition of the muscle and non-muscle portions of shrimp. Arachidonic, eicosapentaenoic, and docosahexaenoic acid contents of muscle and non-muscle portions of shrimp were significantly (P?<?0.05) higher in lysolecithin-supplemented diet compared to soylecithin-supplemented diet. The present results suggest that lysolecithin improved the fatty acid digestibility with its high emulsification properties that reflected in better performance by improving dietary value of palm oil.     

Growth,hematological and biochemical indices of common carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis> fed diets containing corn gluten meal

The effects of replacing fish meal (FM) with corn gluten meal (CGM) on growth and physiological performance were evaluated in common carp (Cyprinus carpio). Six experimental diets were formulated by substituting 0 (control), 20, 40, 60, 80, and 100% CGM protein for FM protein. The concentrations of dietary protein in the experimental diets were 27.8–29% and the P:E ratios were 14.7–15.46 mg/kJ. Eighteen fish with an initial weight of 13.5?±?0.1 g were allocated to each of 18 circular tanks (450 L) to give triplicate groups for each dietary treatment. The fish were fed to satiation for 8 weeks. At the end of the feeding trial, growth indices, body proximate composition, and hematological and biochemical parameters were measured. Blood samples were taken from six fish in each tank. Final weight and total length were significantly higher in fish fed 100% CGM (27.8?±?1.2 g and 11.9?±?0.3 cm) than for those fed the control (22.7?±?1.4 g and 10.9?±?0.5 cm) or 20% CGM (22.3?±?1.2 g and 11?±?0.4 cm) diets. No effect of FM replacement by CGM was observed for condition factor or hepatosomatic index (P?>?0.05). The highest value of protein productive value (14.31?±?0.65) was observed in fish fed 20% CGM (P?<?0.05). There were no significant differences in percentage body moisture and fat, but percentages of protein and ash were significantly different among experimental groups; the highest values of protein (15.6?±?0.24%) and ash (3.01?±?0.26%) were recorded in fish fed 40% CGM. For hematological parameters, the highest number of white blood cells (4.1?±?0.1?×?10³ mm^?3) was observed in fish fed 100% CGM (P?<?0.05). In addition, the highest hematocrit (42.1?±?0.7%) and triglyceride (294.11?±?23.82 mg dl^?1) were seen in fish fed the diet containing 40% CGM, while 80% CGM gave the highest cholesterol level (204.44?±?9.0 mg dl^?1; P?<?0.05). Replacement of FM with CGM had no negative effects on growth and physiological parameters of common carp fingerlings in this short (8 weeks) trial, suggesting that it may be feasible to replace FM with CGM in diets formulated for juvenile common carp.     

Fish meal replacement with squilla (<Emphasis Type="Italic">Oratosquilla nepa</Emphasis>, Latreille) silage in a practical diet for the juvenile giant freshwater prawn, <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> de man, 1879

Replacement of fish meal with squilla silage in practical diet for the juvenile giant freshwater prawn, Macrobrachium rosenbergii, was evaluated. Five iso-nitrogenous and iso-caloric diets were prepared in which protein requirements were met with 100% fish meal (control, diet 1) and squilla silage replacing fish meal at 25, 50, 75 and 100% (diets 2, 3, 4 and 5, respectively). Water stability and water absorption of five feeds revealed significant differences (P?<?0.05). The weight gain varied between a maximum of 248.50?±?34.07% in diet 4 to lowest 132.45?±?14.34% in diet 1. The average daily gain in weight in grams varied from 0.091?±?0.01 (diet 5) to 0.154?±?0.04 (diet 3), whilst the specific growth rate and gross growth coefficient values were recorded highest in diet 4. Highest survival rates (86.66?±?5.77%) were recorded in both experimental diets 4 and 5. Low feed conversion ratio of 1.19?±?0.21 was recorded from diet 4, whilst the highest value of 2.16?±?0.09% was estimated from the diet 5. Proximate carcass composition showed highest crude protein content in post-larvae fed with diet 5 (47.24%) in contrast to lowest diet 1 (36.12%). Lipid values fluctuated significantly between 2.45 and 7.18% (P?<?0.05) between treatments. The ash content significantly increased from diet 1 (16.34%) to diet 5 (20.69%) (P?<?0.05). Highest feed efficiency (gain/feed) value was recorded in diet 4 (1.52?±?0.22), whilst the diet 5 showed lowest value (0.99?±?0.06). The results suggested that squilla silage can be utilised up to 75% of the protein in prawn diets for fish meal replacement.     

Red drum <Emphasis Type="Italic">Sciaenops ocellatus</Emphasis> growth and expression of bile salt-dependent lipase in response to increasing dietary lipid supplementation

Sciaenops ocellatus has a long history in aquaculture and many difficulties associated with its commercial culture have been addressed and successfully resolved; nevertheless, further research in lipid nutrition could address more comprehensive questions on the way these nutrients are utilized. The purpose of this study was to evaluate S. ocellatus growth and lipase gene expression in response to increasing dietary lipid supplementation. Four experimental diets were formulated to provide 3, 10, 16, or 23% lipid using menhaden fish oil. Twenty juveniles (mean initial weight 2.3?±?0.1 g) were stocked per aquaria in a recirculating system; each diet was assigned to three aquaria and fed to fish for 6 weeks. At the end of the study, fish fed 3% of dietary lipid were significantly (P?<?0.0001) smaller and showed significantly lower feed efficiency, condition factor, hepatosomatic index, and intraperitoneal fat than fish fed the other diets, but no differences were observed among fish fed 10, 16, or 23% lipid. A straight broken-line regression model for thermal growth coefficient provided an estimated value of 9.4% of dietary lipid as the optimal inclusion level. The bile salt-dependent lipase (BSDL) of red drum was 80.3 kDa. Relative gene expression of BSDL was significantly higher (P?=?0.0007) in fish fed 10% lipid, with no differences among the other dietary treatments. Results provided could help monitor the metabolic status of farmed fish and contribute to optimize diet formulations based on maximum gene expression of BSDL for supplementation of dietary lipid.     

Effect of dietary chitosan on growth performance,hematological parameters,intestinal histology and stress resistance of Caspian kutum (<Emphasis Type="Italic">Rutilus frisii kutum</Emphasis> Kamenskii, 1901) fingerlings

This study was conducted to investigate the effects of dietary chitosan on growth performance, hematological parameters, intestinal histology, stress resistance and body composition in the Caspian kutum (Rutilus frisii kutum, Kamenskii, 1901) fingerlings. Fish (1.7 ± 0.15 g) were fed diets containing chitosan at different levels (0, 0.25, 0.5, 1 and 2 g kg^?1 diet) for a period of 60 days. Results showed that the feed conversion ratio significantly decreased in fish fed diet containing 1 g kg^?1 of chitosan compared to the other groups (P < 0.05), but there were no significant differences between treatments in terms of specific growth rate and condition factor (P > 0.05). Leukocyte increased in fish fed diet containing 2 g kg^?1 of chitosan compared to the other groups (P < 0.05). Lymphocytes, eosinophils and neutrophils did not significantly change among dietary treatments (P > 0.05). Also, the chitosan supplementation did not affect the whole-fish body composition (P > 0.05). Light microscopy demonstrated that the intestinal villus length increased in fish fed diet containing 1 g kg^?1 of chitosan compared to control group (P < 0.05). While 11 and 13 ‰ salinity and 30 °C thermal stress had no effect, 1 g kg^?1 of chitosan (P < 0.05) showed highest survival rate (70 %) in 34 °C thermal stress. The results showed that chitosan in the diet of the Caspian kutum fingerlings could improve feed conversion ratio, the nonspecific defense mechanisms and resistance to some of the environmental stresses.     

Effects of the supplementation of vitamin D<Subscript>3</Subscript> on the growth and vitamin D metabolites in juvenile Siberian sturgeon (<Emphasis Type="Italic">Acipenser baerii</Emphasis>)

The objective of this study was to evaluate the effects of the supplementation of vitamin D₃ on the growth, vitamin D metabolites, and osteocalcin secretion in juvenile Siberian sturgeon (Acipenser baerii). A 90-day growth trial was conducted with juvenile Siberian sturgeon (initial body weight 3.47 ± 0.14 g) fed seven isonitrogenous and isoenergetic practical diets (45% CP and 13% lipid) containing 60 (basal diet), 240, 450, 880, 1670, 3300, or 1.0 × 10⁵ IU/kg feed (D60~D 1.0 × 10⁵) vitamin D₃. The results showed that weight gain and specific growth rate increased as the dietary vitamin D₃ levels increased from 450 to 3300 IU/kg (P < 0.05). The fish fed with D1670 and D3300 diets had higher crude lipid and ash levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, or D3300 diets had higher 25-OH-D₃ and 1,25-(OH)₂-D₃ levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, D3300, or D1.0 × 10⁵ diets had higher osteocalcin levels than the fish fed the D60 diet (P < 0.05). Based on the broken line method analysis of weight gain and osteocalcin, the dietary vitamin D₃ requirement of juvenile Siberian sturgeon was estimated to be 1683.30 and 1403.27 IU/kg per diet, respectively.     

Effects of dietary organic,inorganic, and nanoparticulate selenium sources on growth,hemato-immunological,and serum biochemical parameters of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>)

An 8-week feeding trial was conducted to compare the effects of supplementing (0.7 mg kg^?1) different dietary selenium (Se) sources including organic [selenomethionine (SeMet)], inorganic [sodium selenite (Na₂SeO₃)], and nanoparticulate Se (nano-Se) on physiological responses of common carp, Cyprinus carpio juveniles (9.7?±?0.1 g). Basal diet without Se supplementation used as control. Fish fed nano-Se supplemented diet had the highest weight gain (97.2?±?10.8%) and feed efficiency ratio (42.4?±?0.8%). Intestinal villi height was significantly taller in fish fed nano-Se diet than in the control group in both foregut and midgut sections. Serum glutathione peroxidase and superoxide dismutase activities were significantly higher in nano-Se and SeMet groups than in control and sodium selenite groups. Fish fed Se-supplemented diets had greater red blood cell counts and hematocrit and hemoglobin values than the control group (P?<?0.05). Nano-Se and SeMet groups showed a significant increase in white blood cell counts, neutrophil percentage, and serum lysozyme activity than the other groups. Fish fed nano-Se diet had the highest serum hemolytic activity, total immunoglobulin, and total protein and albumin contents, as well as the lowest serum total cholesterol and low density lipoprotein levels (P?<?0.05). Overall, significant improvements in growth performance, feed utilization, intestinal morphology, and hemato-immunological and serum biochemical parameters of common carp juveniles suggest nano-Se as an efficient source for providing dietary Se in this species.     

Modulation of appetite,lipid and glucose metabolism of juvenile grass carp (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>) by different dietary protein levels

This study was undertaken to explore the systemic metabolic strategies of juvenile grass carp (Ctenopharyngodon idellus) to maintain growth when fed with different dietary protein levels. The optimal growth group and two growing discomfort groups were selected through the basic data, to explain the growth difference from appetite regulation and lipid and glucose metabolism perspective. Three experimental diets were formulated with three dietary protein levels at 200.3, 296.1 and 442.9 g kg^?1, named P1, P2 and P3, respectively. Juvenile grass carp (initial body weight 12.28 ± 0.14 g) were fed with three diets with 3 replications per dietary treatment in an indoor recirculation system for an 8-week feeding trial. Fish fed with diet P2 dietary group showed significantly higher WG, SGR, FI and PER than other groups. Compared with other groups, mRNA expressions of NPY, Y8a and Y8b in fish fed with P2 significantly down-regulated, while the expressions of CCK and CART in fish fed with P3 significantly down-regulated (P < 0.05). With increasing dietary protein levels, G6Pase, GK, PK and PEPCK were all significantly inhibited (P < 0.05). For lipid metabolism, the mRNA expression of ACC in P1 dietary group was significantly higher than P3 dietary group; besides, LPL expression in P3 group was significantly higher than other two groups (P < 0.05). PPARα expression in P2 was significantly lower than other groups (P < 0.05). These results suggested that grass carp fed with P2 (296.1 g kg^?1 protein level) showed highest weight gain, contributed to more balanced nutrient metabolism and appetite regulation. Too high dietary protein (442.9 g kg^?1) should be avoided because it induced lowest PER, body lipid and liver lipid, and inhibited glucose and lipid metabolism in juvenile grass carp.     

Effects of exogenous non-starch polysaccharide-degrading enzymes in diets containing <Emphasis Type="Italic">Gracilaria lemaneiformis</Emphasis> on white-spotted snapper <Emphasis Type="Italic">Lutjanus stellatus</Emphasis> Akazaki

A feeding experiment was conducted to investigate the effects of exogenous non-starch polysaccharide (NSP)-degrading enzymes in diets containing Gracilaria lemaneiformis (GL) on growth performance and digestive enzyme activities of white-spotted snapper Lutjanus stellatus Akazaki (initial mass 8.0 ± 0.1 g). A basal diet (D0) containing a mixed protein source (fish meal, soybean meal and GL meal) was used as the control. Two diets supplemented with 0.5 g (D1) and 1 g (D2) exogenous NSP-degrading enzymes per kilogram of diet were formulated. Each diet was assigned to triplicate groups of fish in a total of nine floating sea cages (270 fish, 30 fish per cage). After a 60-day feeding trail, significantly higher weight gain, specific growth ratio and feed efficiency ratio were observed in fish fed D2 diet compared to those of control (P < 0.05). Body lipid, moisture and ash contents were not significantly affected by NSP-degrading enzyme supplementation, but significantly higher protein content was noticed in fish fed D2 diet compared to that of control (P < 0.05). The amylase activity in the stomach and intestine was significantly higher in fish fed D2 diet (P < 0.05), but no significant differences were observed in pepsin and lipase activities in the stomach or trypsin and lipase activities in the intestine between all treatments. The results suggested that addition of 1 g kg^?1 NSP-degrading enzymes in diet could efficiently improve seaweed feed utilization and growth performance of white-spotted snapper fish.     

Effects of nucleotides on growth performance,immune response,disease resistance and intestinal morphology in shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> fed with a low fish meal diet

Nucleotides (NT) are widely used as an immunostimulant in aquaculture. A 10-week feeding trial was conducted to evaluate the effects of dietary NT on the growth performance, immune response, disease resistance and intestinal morphology of the Pacific white shrimp Litopenaeus vannamei (initial mean body weight: 0.39 ± 0.00 g). Five isolipidic (about 7 % crude lipid) and isonitrogenous (about 39 % crude protein) practical diets were supplemented with graded levels of NT (0, 60, 90, 120 and 1200 mg kg^?1), respectively. These diets were named as N1, N2, N3, N4 and N5. Each diet was randomly fed to six tanks of shrimps, and each tank contained 40 shrimps. The shrimps were fed four times daily (07:00, 11:00, 16:00 and 21:00 h). The results showed that there were no significant differences in survival, final weight, specific growth rate, feed intake, feed conversion ratio and whole-body compositions among all the treatments (P > 0.05). Shrimps fed the control diet had the significantly lowest activities of superoxide dismutase, total nitric oxide synthase and lysozyme (P < 0.05). However, those parameters increased when dietary NT increased from 60 to 120 mg kg^?1 and decreased as inclusion level increased to 1200 mg kg^?1 (P < 0.05). The cumulative mortality of the shrimps challenged with Vibrio parahaemolyticus was significantly higher in the treatments without dietary NT supplementation than those in treatments with dietary NT (≥90 mg kg^?1) (P < 0.05). The jejunum wall thickness in shrimps fed the control diet was significantly lower than that in the treatments of N2, N3 and N4 (P < 0.05). For the villus height, the highest value (49.29 µm) was found in N3. In summary, the present study showed that 90 mg kg^?1 of dietary NT is the optimum dietary level for good gut health, immune response and disease resistance of Pacific white shrimp fed a diet with 18 % fish meal.     

Modulation of antioxidant defense and immune response in zebra fish (<Emphasis Type="Italic">Danio rerio</Emphasis>) using dietary sodium propionate

The present study explores the effect of dietary sodium propionate on mucosal immune response and expression of antioxidant enzyme genes in zebra fish (Danio rerio). Six hundred healthy zebra fish (0.42 ± 0.06 g) supplied, randomly stocked in 12 aquariums and fed on basal diets supplemented with different levels of sodium propionate [0 (control), 5, 10 and 20 g kg^?1] for 8 weeks. At the end of the feeding trial, mucosal immune parameters (TNF-α, IL-1β, Lyz), antioxidant enzyme (SOD, CAT) as well as heat shock protein 70 (HSP70) gene expression were measured. The results revealed feeding on sodium propionate significantly up-regulated inflammatory response genes (TNF-α, IL-1β, Lyz) in a dose-dependent manner (P < 0.05). However, antioxidant enzyme genes significantly down-regulated in the treated group compared with control (P < 0.05). Also, HSP70 gene expression was higher in the liver of fish fed the basal diet and deceased with elevation of sodium propionate levels in the diet. These results showed beneficial effects of dietary sodium propionate on mucosal immune response as well as the antioxidant defense of zebra fish.     

Effects of dietary essential amino acid deficiencies on the growth performance and humoral immune response in silvery‐black porgy (Sparidentex hasta) juveniles

A 6‐week feeding trial was conducted for determining the effects of dietary essential amino acids (EAA) deficiencies on growth performance and non‐specific immune responses in silvery‐black porgy juveniles (4.7 ± 0.1 g initial weight). Eleven isoproteic (ca. 47%) diets were formulated including a control diet containing the optimum quantity of EAA, and ten EAA‐deficient diets. All diets contained 36% fish meal and 18.5% crystalline EAA and non‐essential amino acids (NEAA) as the main source of dietary proteins. All the EAA and NEAA incorporated in the crystalline amino acids mixture of the control diet simulated the amino acids profile of the fish meal. The other 10 EAA‐deficient diets were formulated by the deletion of each of the 10 EAA (crystalline form) from the control diet and replaced by a mixture of NEAA for the adjustment of dietary nitrogen contents. At the end of the experiment, fish fed with threonine‐deficient diet showed the lowest survival rate (p < .05), whereas growth performance decreased in fish fed all EAA‐deficient diets, although the reduction in body growth varied depending on the EAA considered. Plasma total protein decreased in all experimental groups except for fish fed the phenylalanine‐deficient diet. Fish fed with arginine‐ and lysine‐deficient diets had the lowest plasma C3, C4, lysozyme, total immunoglobulin and total superoxide dismutase activity (p < .05). Present results indicated that lysine, methionine and threonine were the most limiting EAA in terms of growth performance; however, arginine, threonine and lysine were the most limiting EAA for innate immunity responses in silvery‐black porgy juveniles.     

Comparative evaluation of fermented and non-fermented de-oiled rice bran with or without exogenous enzymes supplementation in the diet of <Emphasis Type="Italic">Labeo rohita</Emphasis> (Hamilton, 1822)

A 60-day feeding trial was conducted to study the effect of exogenous enzymes (xylanase and phytase) supplementation in the non-fermented and fermented de-oiled rice bran (DORB)-based diet of Labeo rohita. Four test diets (T1-DORB-based diet, T2-fermented DORB-based diet, T3-phytase and xylanase supplemented DORB-based diet, and T4-phytase and xylanase supplemented fermented DORB-based diet) were formulated and fed to the respective groups. Test diets T3 and T4 were supplemented with 0.01% xylanase (16,000 U kg^?1) and 0.01% phytase (500 U kg^?1) enzymes. One hundred twenty juveniles of L. rohita, with an average weight 5.01?±?0.02 g, were stocked in 12 uniform size plastic rectangular tanks in triplicate with 10 fishes per tank following a completely randomized design (CRD). Exogenous enzyme supplementation to the T3 group significantly improved the growth performance of L. rohita (p?<?0.05). Fermented DORB fed groups registered significantly lower growth irrespective of the supplementation of exogenous enzymes. The carcass composition (except CP %), enzyme activities (except amylase activity), globulin, and A/G ratio did not vary significantly (p?>?0.05). Based on the results of the present study, it is concluded that exogenous enzyme supplementation significantly increases the growth of fish fed with DORB-based diet.     

Bait-subsidized diets and their effects on ovigerous North American lobsters (<Emphasis Type="Italic">Homarus americanus</Emphasis>)

Ovigerous American lobsters (Homarus americanus) display a protracted period of ovary maturation and maternal care when incubating their eggs, potentially influencing offspring fitness. Lobsters consume a wide range of food items; however, trap bait may comprise a larger proportion of their diet in some fished areas compared to non-fished areas, and the long-term consequences of a bait-based diet remain largely unexplored in lobsters. We tested the hypothesis that disproportionate amounts of bait in the diets of pre-ovigerous females affect the quality of their ovaries and eggs. We held pre-ovigerous lobsters (n?=?29) over a period of ~?300 days (range?=?270–378) and fed them diets of herring bait, natural prey items (crab, mussel, urchin, macroalgae), or a combination of both diet types. Nutritional status, measured as biweekly blood indices and total glucose levels, suggest differences between lobsters fed a natural or combination diet and lobsters fed a bait-based diet (ANOVA; P?<?0.05). We found that bait diets contained more protein (58.5%) and lipids (31.6%) compared to natural diets (34.5 and 13.2%, respectively) and lipid levels in ovaries and eggs significantly correlated with each other for all treatments (r?=?0.76, n?=?15, P?=?0.028). Histopathological analysis indicates that ovaries contained more variable maturation in starved lobsters or those fed with bait, with some animals showing delayed gonad maturation. Results suggest that a varied diet promotes the overall fitness of ovigerous lobsters and the associated reserves that are used for ovarian development and subsequent oocyte formation.     

Growth performance and biochemical composition of juvenile pearl oyster <Emphasis Type="Italic">Pinctada martensii</Emphasis> fed on artificial diets

The effects of three artificial diets (S1, S2 and S3) on survival, growth and biochemical composition of one-year-old pearl oyster Pinctada martensii were investigated. Six experimental groups (EG1, EG2, EG3, EG4, EG5 and EG6) and one control group (CG) were set up. EG1, EG2 and EG3 were solely fed on S1, S2 and S3, respectively. EG4, EG5 and EG6 were fed on mixed diets, as follows: S1 and Platymonas subcordiformis; S2 and P. subcordiformis; and S3 and P. subcordiformis, respectively. CG was fed on only P. subcordiformis. All groups were continuously fed for 60 days. Survival, growth and biochemical composition of soft tissues were compared across the groups. Results showed that survival rate, the absolute growth rate (AGR) and relative growth rate (RGR) of shell length did not differ significantly across the groups (p > 0.05). The AGR and RGR of total weight differed significantly among the groups (p < 0.05). AGR and RGR of shell length and total weight were the highest in EG5 and the lowest in EG1. Gross fat content showed insignificant differences among the groups (p > 0.05). However, gross protein content and ash content showed significant differences across the groups (p < 0.05). The gross protein of the groups solely fed on artificial diets was lower than those of the groups fed on mixtures of artificial diets and microalgae or single microalgae. The contents of other amino acids, total amino acids (TAAs) and essential amino acids (EAAs) showed significant differences across the groups (p < 0.05). TAA, EAA and delicious amino acids of the groups fed solely on artificial diets were lower than those of the groups fed on mixtures of artificial diets and microalgae or single microalgae. Results indicated that the artificial diet (S2) can serve as substitutes of microalgal diets for P. martensii.     

Evaluation of different <Emphasis Type="Italic">Pyropia yezoensis</Emphasis> extracts as feed additives for growth and immunity of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

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.     

Aflatoxin B<Subscript>1</Subscript> (AFB<Subscript>1</Subscript>) reduces growth performance,physiological response,and disease resistance in Tra catfish (<Emphasis Type="Italic">Pangasius hypophthalmus</Emphasis>)

Triplicate groups of one hundred Tra catfish (8 g?±?0.2) were fed seven test diets containing increasing levels of AFB₁ (0, 50, 100, 250, 500, and 1000 μg AFB₁ kg^?1). Additionally Mycofix® Secure was added at 1.5% to one diet containing 500 μg AFB₁ kg^?1. Results showed that Tra catfish are sensitive to AFB₁. Reduction in weight gain (P?<?0.05) was observed for fish fed 50 μg AFB₁ kg^?1 and declined further with increasing levels of AFB₁ in the diets. Fish fed diets contaminated with 500 and 1000 μg AFB₁ kg^?1 showed increased (P?>?0.05) hepatosomatic index (HIS), while an increase in adipose somatic index (ASI) was observed in fish fed 50 μg AFB₁ kg^?1 and above when compared to the control and Mycofix® diets. After 12 weeks, blood serum analysis revealed higher alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in fish fed the 50, 100, and 250 μg AFB₁ kg^?1 suggesting occurrence of liver damage. Disease resistance of fish exposed to Edwardsiella ictaluri was also compromised by the presence of AFB₁ in the feed and was directly related to the contamination level. Seven days after Edwardsiella ictaluri exposure, survival rates were 50, 41.7, 31.7, and 8.3% for fish fed control, 50, 100, and 250 μg AFB₁ kg^?1, respectively. This trial shows that AFB₁ at a level of 50 μg AFB₁ kg^?1 and above can affect fish performance and disease resistance. Application of an effective mycotoxin management in the feed seems to be useful to prevent the negative effects of AFB₁.     

Effect of <Emphasis Type="Italic">Lactococcus lactis</Emphasis> K-C2 on the growth performance,amino acid content and gut microflora of amberjack <Emphasis Type="Italic">Seriola dumerili</Emphasis>

This study aimed to evaluate the effect of Lactococcus lactis K-C2 on the growth performance, microbial diversity, and release of free amino acids in the intestinal tract and the edible parts of young amberjack, Seriola dumerili. Fish were fed a diet with or without strain K-C2 (2?×?10¹⁰ cfu/g feed) for 25 days. The results indicated that the growth performance of fish in the treated group was significantly higher than those in the control group (p?<?0.05). The amount of five amino acids (aspartate, sarcosine, taurine, alanine, and arginine) in the gut content and 13 of 21 amino acids in the edible parts of fish in the treated group were significantly higher (p?<?0.05) than those in the control group. Sphingomonas, Propionibacterium, and Mycobacterium were observed in gut microflora of fish in both the control and treated groups. Staphylococcus and Kocuria were detected in one sample from the control and treated groups; Acinetobacter and Acidobacteria were found in one sample from the control group. L. lactis was only found in one sample in the treated group. In conclusion, the dietary administration of probiotic L. lactis stimulated growth, reduced feed consumption, and improved the nutritional value of cultured amberjack.     

Physiological response,blood chemistry profile and mucus secretion of red sea bream (<Emphasis Type="Italic">Pagrus major</Emphasis>) fed diets supplemented with <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> under low salinity stress

Environmental stressors caused by inadequate aquaculture management strategies suppress the immune response of fish and make them more susceptible to diseases. Therefore, efforts have been made to relieve stress in fish by using various functional feed additives in the diet, including probiotics. The present work evaluates the effects of Lactobacillus rhamnosus (LR) on physiological stress response, blood chemistry and mucus secretion of red sea bream (Pagrus major) under low salinity stress. Fish were fed four diets supplemented with LR at [0 (LR0), 1 × 10² (LR1), 1 × 10⁴ (LR2) and 1 × 10⁶ (LR3) cells g^?1] for 56 days. Before stress, blood cortisol, urea nitrogen (BUN) and total bilirubin (T-BIL) showed no significant difference (P > 0.05), whereas plasma glucose and triglyceride (TG) of fish-fed LR2 and LR3 diets were significantly lower (P < 0.05) than those of the other groups. Plasma total cholesterol (T-CHO) of fish-fed LR3 diet was significantly (P < 0.05) lower than that of the other groups. Furthermore, total plasma protein, mucus myeloperoxidase activity and the amount of mucus secretion were significantly enhanced in LR-supplemented groups when compared with the control group (P < 0.05). After the application of the low salinity stress test, plasma cortisol, glucose, T-CHO and TG contents in all groups showed an increased trend significantly (P < 0.01) compared to the fish before the stress challenge. However, plasma total protein and the amount of secreted mucus showed a decreased trend in all groups. On the other hand, BUN, T-BIL and mucus myeloperoxidase activity showed no significant difference after exposure to the low salinity stress (P > 0.05). In addition, the fish that received LR-supplemented diets showed significantly higher tolerance against low salinity stress than the fish-fed LR-free diet (P < 0.05). The physiological status and the detected immune responses, including total plasma protein and mucus myeloperoxidase activity in red sea bream, will provide a more comprehensive outlook of the effects of probiotics to relieve stress in fish.