Immunostimulatory effects of dietary fructooligosaccharides on red swamp crayfish,Procambarus clarkii (Girard)

Fructooligosaccharides (FOS) are widely researched as prebiotics and immunostimulants in humans and terrestrial animals. However, limited researches on immune functions of FOS were reported in crustacean. In the present study, red swamp crayfish Procambarus clarkii were fed with different concentrations of FOS (2.0, 5.0, 8.0, 10.0 g kg^?1 diet), and then the immunostimulatory effects of FOS were evaluated by measuring immune parameters and examining immune‐related gene expression. PO and SOD activities were significantly increased in groups fed with 8.0 or 10.0 g kg^?1 of FOS compared with those in control group. In addition, significant elevations of SOD and phagocytic activities were also observed in group fed with 5.0 g kg^?1 of FOS. Among examined immune‐related genes, expressions of crustin1, lysozyme, SOD and pro‐PO were significantly up‐regulated by feeding with 8.0 or 10.0 g kg^?1 of dietary FOS. Survival rates of crayfish challenged with Aeromonas hydrophila were significantly improved by feeding with 5.0, 8.0 or 10.0 g kg^?1 of dietary FOS for 30 days. Phagocytic activities and bacterial clearance efficiencies were also significantly increased in groups fed with 8.0 or 10.0 g kg^?1 of FOS. The results indicated that dietary FOS effectively induced innate immune responses of red swamp crayfish in a dose‐dependent way and could be used as potential immunostimulant in crustacean.     

Immunostimulatory effects of N‐Oxide–Quaternary alkaloid fraction of a marine Chlorophycean macroalga in the striped murrel,Channa striata (Bloch)

N‐Oxide–Quaternary Alkaloid Fraction (NOQAF) of a Chlorophycean macroalga, Caulerpa scalpelliformis (R.Br.) C. Ag f. denticulata (Deaisne) Weber van Bosse (Patent filed) was intraperitoneally administered at different doses (0, 2, 20 or 200 mg kg^?1 body weight) in different groups of Channa striata to assess its effect on the non‐specific immune responses and disease resistance against live virulent Aeromonas hydrophila. A reference positive control [MacroGard (Biotec Pharmacon ASA, Norway) 20 mg kg^?1 body weight] was simultaneously maintained to compare its efficacy. The fraction (NOQAF) has been found to enhance the serum lysozyme, peroxidase, antiprotease and alternate complement activities and the reactive oxygen and nitrogen species production and peroxidase activity by the peripheral blood leucocytes than the control group during the study period. On experimental challenge with live virulent A. hydrophila, maximum RPS values of 88.8 and 87.4 were noted in the groups treated with single dose of 20 mg kg^?1 and double dose of 2 mg kg^?1 of NOQAF respectively. In conclusion, the intraperitoneal administration of the N‐Oxide–Quaternary Alkaloid Fraction (NOQAF) of C. scalpelliformis has been found to significantly enhance the non‐specific immune responses and disease resistance against A. hydrophila in Channa striata.     

Dietary administration of natural immunostimulants on growth performance,haematological, biochemical parameters and disease resistance of Asian Sea bass Lates calcarifer (Bloch, 1790)

This study was aimed to address the promising evaluation of Cissus quadrangularis plant (stem) and lipopolysaccharide (LPS from bacteria) supplemented diets on innate immune response in Lates calcarifer fingerlings against Aeromonas hydrophila infection. Fingerlings were fed supplemented diets containing four different concentrations of C. quadrangularis (0.5, 1.0, 1.5 and 2.0 g kg^?1 feed), LPS (25, 50, 75 and 100 mg kg^?1 feed) and control (normal formulated diet) for 60 days. The fish fingerlings fed supplemented diet displayed significant differences (P < 0.05) in specific growth rate (SGR) and relative percentage survival compared to the control group fed without C. quadrangularis and LPS‐supplemented diet. Fingerlings were injected intraperitoneally with 100 μL lethal dose of A. hydrophila containing 1 × 10⁶ CFU g^?1. Supplementation of C. quadrangularis and LPS diet significantly increased biochemical profile such as protein, lipid and carbohydrate content, haematological parameters of L. calcarifer fingerlings in different experimental periods when compared with the control group. Dietary doses of C. quadrangularis and LPS‐supplemented diet significantly influenced growth performance and increased survival rate in L. calcarifer fingerlings against A. hydrophila infection.     

Purified deoxynivalenol or feed restriction reduces mortality in rainbow trout,Oncorhynchus mykiss (Walbaum), with experimental bacterial coldwater disease but biologically relevant concentrations of deoxynivalenol do not impair the growth of Flavobacterium psychrophilum

Diets containing deoxynivalenol (DON) were fed to rainbow trout Oncorhynchus mykiss (Walbaum) for 4 weeks followed by experimental infection (intraperitoneal) with Flavobacterium psychrophilum (4.1 × 10⁶ colony‐forming units [CFU] mL⁻¹). Mortality of rainbow trout fed either 6.4 mg kg⁻¹ DON or trout pair‐fed the control diet was significantly reduced (P < 0.05) in comparison with trout fed the control diet to apparent satiation (<0.1 mg kg⁻¹ DON). In a second experiment, trout were fed one of three experimental diets; a control diet, a diet produced with corn naturally contaminated with DON (3.3 mg kg⁻¹ DON) or a diet containing purified DON (3.8 mg kg⁻¹); however, these fish were not experimentally infected. The presence of DON resulted in significant reduction (P < 0.0001) in feed intake as well as weight gain after 4 weeks. Respiratory burst of head‐kidney leucocytes isolated from rainbow trout fed diets containing purified DON (3.8 mg kg⁻¹) was significantly higher (P < 0.05) at 35 day post‐exposure compared with controls. The antimicrobial activity of DON was examined by subjecting F. psychrophilum in vitro to serial dilutions of the chemical. Complete inhibition occurred at a concentration of 75 mg L⁻¹ DON, but no effect was observed below this concentration (0–30 mg L⁻¹).     

Haemato‐immunological response of Labeo rohita (Hamilton) fingerlings fed leaf extracts and challenged by Aeromonas hydrophila

A 35 days feeding trial was conducted to assess the haemato‐immunological response of Labeo rohita fingerlings fed ethanolic leaf extracts of Psidium guajava and Mangifera indica, and infected with Aeromonas hydrophila. Six iso‐nitrogenous (354.6–361.6 g kg^?1) purified diets were prepared with graded level of leaf extracts viz., control (basal feed without any extract); TG‐5 (5 g kg^?1 guava extract); TG‐10 (10 g kg^?1 guava extract); TM‐5 (5 g kg^?1 mango extract); TM‐10 (10 g kg^?1 mango extract); and TGM (5 g kg^?1 guava extract +5 g kg^?1 mango extract). Haematological, immunological, biochemical, along with antioxidant enzyme activities were examined after a 35 day‐feeding trial and following a 7 day challenge with A. hydrophila. The haemoglobin, total leucocyte and erythrocyte counts, respiratory burst activity, lysozyme, total protein, albumin and globulin contents increased significantly (P < 0.05) in leaf extracts fed groups compared with the control in pre‐ and post‐challenge conditions. A significant (P < 0.05) decrease was observed in SOD (superoxide dismutase) and catalase activities of the treatment groups compared with the higher value in control. The trends in mortality indicated that groups of fish showing significantly elevated haemato‐immunological responses had the lowest mortality following challenge with A. hydrophila. The results showed that extracts of P. guajava and M. indica appear to be potential immunostimulant at an inclusion level of 5 g kg^?1 in the diet of rohu. But, mixing of both the extract at similar level did not show any synergistic effect, which needs to be tested at its lower level of inclusion.     

Pharmacokinetic model of florfenicol in turbot (Scophthalmus maximus): establishment of optimal dosage and administration in medicated feed

The pharmacokinetics of florfenicol (FF) in turbot (Scophthalmus maximus) was studied after single intravenous (10 mg kg⁻¹) and oral (100 mg kg⁻¹) administration. The plasma concentration–time data of florfenicol were described by an open one‐compartment model. The elimination half‐life (t_1/2) was estimated to be 21.0 h, and the total body clearance, Cl, was determined as 0.028 L kg h⁻¹. The apparent volume distribution (V_d) was calculated to be 0.86 L kg⁻¹ and the mean residence time (MRT_iv) was 30.2 h. Following oral administration, the maximum plasma concentration (C_max) of 55.4 μg mL⁻¹ was reached at 12 h (T_max). The absorption constant (k_a) was 0.158 h⁻¹. The bioavailability was estimated to be 57.1%. The low bioavailability observed at higher doses was explained by the saturation of the mechanisms of absorption. The drug absorption process was limited by its inherent low solubility, which limited the amount of available FF absorbed in the gastrointestinal tract. Based on the pharmacokinetic data, an optimal dosing schedule for FF administration is hereby provided. Based on the minimum inhibitory concentration found for susceptible strains of Aeromonas salmonicida, oral FF administration of first, an initial dose of 30 mg FF kg⁻¹, followed by 6 maintenance doses at 18 mg kg⁻¹/daily could be effective against furunculosis in turbot.     

Effect of Lactobacillus plantarum and Jerusalem artichoke (Helianthus tuberosus) on growth performance,immunity and disease resistance of Pangasius catfish (Pangasius bocourti,Sauvage 1880)

This study evaluated the effects of Jerusalem artichoke (JA) and Lactobacillus plantarum singly or combined on growth, immunity and disease resistance of Pangasius bocourti. In the first experiment, different concentrations of JA (0, 5, 10, 20, 40, 80 and 160 g kg^?1) were administered to determine an optimal concentration on growth of P. bocourti. In the second experiment, the optimal concentration of JA (5 g kg^?1) was combined with 10⁸ cfu g^?1 L. plantarum. In the final experiment, five randomly selected fish from the second experiment were challenged with Aeromonas hydrophila. Treatments for second and third experiments were 0 g kg^?1 JA (Diet 1), 5 g kg^?1 JA (Diet 2), 10⁸ cfu g^?1 L. plantarum (Diet 3) and 5 g kg^?1 JA + 10⁸ cfu g^?1 L. plantarum (Diet 4). Fish fed 5 g kg^?1 JA or 10⁸ cfu g^?1 of L. plantarum significantly improved specific growth rate (SGR), feed conversion ratio (FCR), serum lysozyme activity and postchallenge survival rate (PCSR). Dietary in the combination of JA and L. plantarum showed significantly enhanced SGR, FCR, serum lysozyme, phagocytosis, respiratory burst activities and PCSR compared with control and individual applications. Dietary JA and L. plantarum significantly stimulated growth, immunity and disease resistance of P. bocourti.     

Effects of continuous and alternate administration of β‐glucan and mannan‐oligosaccharide on the growth,immunity and resistance against Vibrio splendidus of sea cucumber Apostichopus japonicus (Selenka)

A 4‐week growth trial was conducted to compare the effects of different feeding strategies of dietary immunostimulants on the growth, immunity and resistance against Vibrio splendidus of sea cucumbers Apostichopus japonicus (Selenka). Six feeding strategies were set, including feeding immunostimulants‐free diet continuously (control), feeding dietary β‐glucan (1.25 g kg^?1 diet) continuously, feeding dietary mannan‐oligosaccharides (MOS; 2.00 g kg^?1 diet) continuously, feeding β‐glucan 2 days followed by MOS 5 days alternately, feeding β‐glucan 5 days followed by MOS 2 days alternately and feeding β‐glucan 7 days followed by MOS 7 days alternately. The sea cucumbers fed immunostimulants showed higher specific growth rate (SGR) and lower cumulative mortality than control (P < 0.05). When sea cucumbers were fed with β‐glucan continuously, total coelomocytes counts and superoxide anion were significantly higher than control on the 4th day (P < 0.05). However, these two immune parameters were not significantly higher than those in control after the 18th day (P > 0.05). While sea cucumbers continuously fed MOS, these two immune parameters were not significantly higher than control until the 15th day. All immune parameters of the sea cucumbers fed with β‐glucan and MOS alternately were significantly higher than those in control during the experiment (P < 0.05). The sea cucumbers fed with β‐glucan 7 days followed MOS 7 days alternately showed the highest SGR and second lowest cumulative mortality. It was suggested that this feeding strategy is most suitable for sea cucumbers.     

Effect of dietary chitosan on growth performance,haematology, immune response,intestine morphology,intestine microbiota and disease resistance in gibel carp (Carassius auratus gibelio)

A 75‐day experiment was conducted with juvenile gibel carp (Carassius auratus gibelio) (4.80 ± 0.01 g) to evaluate effects of dietary chitosan on fish growth performance, haematology, intestine morphology and immune response. Six isonitrogenous (crude protein: 383 g kg^?1), isolipid (97.5 g kg^?1) and isocaloric (gross energy: 16.7 kJ g^?1) diets were formulated to contain 0, 1800, 4000, 7500, 10 000, 20 000 mg kg^?1 chitosan, respectively. The results showed that the growth was depressed when the fish fed with 10 000 mg kg^?1 chitosan. Serum cholesterol, triglyceride and low‐density lipoprotein decreased in 10 000 and 20 000 mg kg^?1 chitosan. On day 75, blood leucocyte phagocytic activity respiratory burst and alternative pathway of complement haemolytic activity were enhanced in 4000 mg kg^?1 chitosan. The number of goblet cell, intraepithelial lymphocyte of mid‐intestine and microvilli height of distal intestine increased at 4000 mg kg^?1 dietary chitosan. Dietary chitosan modulated intestine microbiota, depressed pathogen bacteria Aeromonas veronii‐like and improved Cellulomonas hominis‐like, Bacillus oceanisediminis‐like and two uncultured bacterium‐like species on day 75. Dietary 7500 and 10 000 mg kg^?1 chitosan enhanced the protection against Aeromonas hydrophila infection. In conclusion, oral administration of dietary 7500 mg kg^?1 chitosan for 75 days is recommended for the survival of gibel carp.     

A tolerance and safety assessment of daidzein in a female fish (Carassius auratus gibelio)

Daidzein is widely used in farmed animals as a dietary additive. However, limited information is available about its use in aquaculture. The effects of daidzein inclusion in the diet of gibel carp was assessed in terms of growth performance, immune response, disease resistance, antioxidant activity, hormone levels, daidzein tissue residues, as well as intestinal and liver morphology. The dietary daidzein inclusion levels were 0, 40, 200 and 400 mg kg^?1 and six replicates of 30 fish were used for each group. No mortality was observed during the 80‐day feeding trial. The growth performance of experimental fish was not significantly affected by dietary daidzein supplementation. However, the non‐specific immune responses, resistance to Aeromonas hydrophila, antioxidant activities, 17β‐oestradiol level, vitellogenin concentration, gonadosomatic index (GSI) and intestinal morphology were significantly affected by dietary daidzein. A dietary dose of 400 mg kg^?1 daidzein significantly decreased the GSI, increased 17β‐oestradiol and vitellogenin concentrations, and impaired the intestinal structure. The daidzein residue in muscle of gibel carp was increased by the high level (400 mg kg^?1) of dietary daidzein. Equol was not detected in fish muscle among all treatments. The present study proved that 40 mg kg^?1 daidzein was safe to be included in diets of gibel carp, and a safety margin of 5 folds of the use‐level (40 mg kg^?1) was determined.     

Enhancement of non‐specific immune responses and disease resistance on oral administration of Nyctanthes arbortristis seed extract in Oreochromis mossambicus (Peters)

The immunomodulatory effect of the seed extract of an Indian medicinal plant Nyctanthes arbortristis L. (NAT) on non‐specific immune responses and disease resistance of tilapia, Oreochromis mossambicus was investigated. Chloroform extract was administered orally as a feed supplement at doses of 0.01%, 0.1% or 1% for 3 weeks. Non‐specific immune parameters such as serum lysozyme and alternate complement haemolytic (ACH₅₀) activities, and cellular reactive oxygen species (ROS), reactive nitrogen intermediate (RNI) and myeloperoxidase production and disease resistance against live virulent Aeromonas hydrophila were investigated after 1, 2 or 3 weeks of feeding with chloroform extract‐supplemented diet. The results of this study indicated that feeding tilapia for 2 weeks with selected doses of chloroform extract of NAT seeds significantly enhanced serum lysozyme, alternate complement activities and cellular ROS, RNI and MPO production. It was evident from the disease resistance test that feed supplemented with NAT seed extract at 0.1% or 1% level significantly reduced the mortality of O. mossambicus and a 3‐week feeding with 0.1% extract‐supplemented diet appears to be the optimal regimen for maximal disease resistance. Thus, the study indicates the scope of using the NAT extract as an immunoprophylactic in finfish aquaculture.     

Antibacterial efficacy and pharmacokinetic evaluation of sanguinarine in common carp (Cyprinus carpio) following a single intraperitoneal administration

Sanguinarine (SA), with antimicrobial and antiparasitic activities against fish pathogens, exhibits great potential commercial use in aquaculture. However, little information on pharmacokinetics of SA restricts further application in aquaculture. In this study, pharmacokinetics of SA in common carp (Cyprinus carpio) following a single intraperitoneal administration [10 mg kg^?1 BW (body weight)] was evaluated by high‐performance liquid chromatography (HPLC). The peak concentration (C_max) of SA in kidney was 11.8 μg g^?1, which was higher than in other tissues and plasma. The terminal half‐life in fish tissue and plasma was as follows: 42.3 h (kidney) > 37.2 h (liver) > 20.1 h (gill) > 18.8 h (muscle) > 10.9 h (spleen) > 10.0 h (plasma). Additionally, we determined the bacterial loads in tissues of common carp infected with Aeromonas hydrophila after i.p. administration of SA at 0, 5, 10 and 20 mg kg^?1 BW. The results showed that i.p. administration of SA at 10 mg kg^?1 BW significantly enhanced antibacterial efficacy against A. hydrophila, where the antibacterial ratio in the gill, kidney, spleen and liver on day 5 was 95.13%, 93.33%, 90.09% and 92.82%, respectively. Overall, these results suggested the potential of SA to treat A. hydrophila infection in common carp farming industry.     

Protective effects of basil (Ocimum basilicum) ethanolic extract supplementation diets against experimental Aeromonas hydrophila infection in common carp (Cyprinus carpio)

This study evaluated the effects of basil (Ocimum basilicum) leaves extract supplement on growth, blood parameters and resistance to Aeromonas hydrophila in Cyprinus carpio fingerlings. Basil leaves were mixed thoroughly with feed at 0, 100, 200, 400, 800 and 1600 mg kg^?1 of diet and were fed in triplicate group for 2 months. At the end of this period, growth performance and survival were determined. Then fish were challenged intraperitoneally with A. hydrophila and mortalities were recorded up to 10 days post challenge. Results indicated that WBC, RBC, Ht, Hb, total protein, albumin and globulin were higher (P < 0.05) in fish fed diets containing O. basilicum compared with the control. Highest specific growth rate values were observed in 400 mg kg^?1 group. Feed conversion ratio was significantly lower (P < 0.05) in fingerlings fed 400 and 800 mg O. basilicum kg^?1 dry diet. After 10 days post challenge, total protein, WBC, RBC and Hb were significantly higher in 400 mg kg^?1 compared with other groups. These results reveal that a dietary O. basilicum leaves extract of 400 mg kg^?1 fed for 60 days leads to increased growth performance and survival rate as well as improved feeding efficiency in common carp fingerlings rendering them more resistant against infection by A. hydrophila.     

Immune effects of bathing European eels in live pathogenic bacteria,Aeromonas hydrophila

The specific and non‐specific immune parameters and protection of European eels (Anguilla anguilla) were evaluated after bathing eels with Aeromonas hydrophila. Two hundred eels were distributed into two equal groups and bathed with Phosphate‐buffered saline (Control group) or 1.0 × 10⁷ cfu mL^?1 A. hydrophila (Test group) for 1 h respectively. Then, eels were bled aseptically from the caudal sinus on 1, 4, 7, 14 and 28 days post treatment. The blood cells were used to evaluate the cellular immunity and the serum was used to determine the titres of specific antibody as well as the activities of superoxide dismutase (SOD) and lysozyme. Eels from both groups were challenged by intraperitoneal injection of 1.0 × 10⁷ cfu of A. hydrophila on 28 and 42 days post bathing. The results show that eels bathed in A. hydrophila significantly (P < 0.05) enhanced the proliferation of different types of blood cells and the serum titres of anti‐A. hydrophila antibody. The Relative Percent Survival (RPS) after challenge on 28 and 42 days post bathing in Test group vs. Control group was 40% and 50% respectively. These results suggest that bathing European eels in A. hydrophila would positively affect specific as well as non‐specific immune parameters and protect against A. hydrophila infection in freshwater farming.     

Microcystis aeruginosa (Kütz) incorporated diets increase immunity and survival of Indian major carp Labeo rohita (Ham.) against Aeromonas hydrophila infection

The aim of this study was to evaluate dietary dosages of Microcystis on the immune response and disease resistance against infections due to the opportunistic pathogen Aeromonas hydrophila in Labeo rohita fingerlings. Labeo rohita fingerlings were fed diet containing 0 (Control), 0.5, 1.0 and 5 g Microcystis powder kg^?1 dry diet for 90 days. Three replicate groups of fish averaging 20 ± 2 g were fed for 3 months daily. At 30 days interval, samples were assayed for different biochemical [serum total protein, albumin, globulin, albumin:globulin (A:G) ratio] and immunological (superoxide anion production, lysozyme and serum bactericidal activity) parameters. The results demonstrate that fish fed Microcystis showed increased levels of lysozyme, serum bactericidal activity, serum protein and albumin (P ≤ 0.05) as compared with the control group. After 90 days, fish were challenged with A. hydrophila and mortality (%) was recorded up to day 10 postchallenge. The group fed 1.0 g Microcystis kg^?1 dry diet showed the highest percentage survival (72%). These results indicate that Microcystis aeruginosa stimulates the immunity and makes L. rohita more resistant to infection by A. hydrophila when fed in dried form in feed.     

Nucleotide promotes feed intake and protein utilization via regulating the gene expression of feeding and nitrogen metabolism in juvenile Chinese perch (Siniperca chuatsi)

Nucleotide (NT) could enhance growth, feeding and immunity in higher vertebrate and fish. Chinese perch (Siniperca chuatsi) refuse artificial diet in natural water, whereas the NT might promote its feeding of domestication diet. The present study was designed to investigate the effect of dietary NT on growth, feed intake, feed utilization, body composition, serum biochemistry and nitrogen metabolism in juvenile Siniperca chuatsi. 0, 0.5, 1.0, 1.5, 2.0 and 4.0 g NT kg^?1 diet were supplemented in each diet, respectively. Triplicate groups of Chinese perch (36.21 ± 0.98 g) were fed twice a day to apparent satiation for 8 weeks. The results showed that fish fed with 1.5 g NT kg^?1 diet had the highest weight gain (WG), specific growth rate, feed efficiency, feed intake, protein efficiency ratio and protein retention efficiency. The crude protein content in whole body was highest in fish fed the diet containing 1.5 g NT kg^?1 diet. Dietary NT supplementation significantly increased the neuropeptide Y gene expression and significantly decreased the agouti‐related protein and pro‐opiomelanocortin gene expressions in brain. NT supplementation decreased urea nitrogen content, aspartate aminotransferase (AST) and alanine aminotransferase activities in serum. The hepatic AST activity was increased first and then decreased, and the highest activity was observed in fish fed with 1 g NT kg^?1 diet. Inversely, the activity of glutamate dehydrogenase (GDH) in liver and adenosine 5′‐monophosphate deaminase in muscle decreased first and then increased, and the lowest activity was observed in fish fed with 1.5 g NT kg^?1 diet. Similarly, the gene expression levels of GDH and arginase in liver were lowest in fish fed with 1.5 g NT kg^?1 diet. Based on the broken‐line regression analysis of WG in the present experimental condition, 1.44 g NT kg^?1 diet was the optimum supplementation level in juvenile Siniperca chuatsi.     

Effects of temperature and dietary protein on gene expression of Hsp70 and Wap65 and immunity of juvenile mirror carp (Cyprinus carpio)

Juvenile mirror carp were fed diets containing 303.4, 321.7, 341.2, 361.0 and 379.1 g kg^?1 proteins, respectively, and reared at different water temperatures (18, 23 and 28°C) for 60 days. Gene expression of heat shock protein gene (Hsp70) and the warm temperature acclimation‐related 65 kDa protein gene (Wap65), immunity and antioxidant status in the carp were investigated. Results indicated that the contents of serum complement 3 (C3), complement 4 (C4) and immunoglobulin M (IgM), as well as activities of liver superoxide dismutase (SOD) and lysozyme (LSZ) were significantly enhanced with increasing dietary protein (P < 0.05), while content of malondiadehyde (MDA) decreased. Gene expression level of Wap65 in the liver significantly increased with dietary protein, while gene expression of Hsp70 decreased. The contents of C3, C4 and IgM, the activities of SOD and LSZ and gene expression level of Wap65 in the liver significantly increased with temperature. These results suggest that: Serum immune parameter, antioxidant enzymes and Hsp70 and Wap65 expression interact in fish to improve ability to adapt to the environment; and the optimal conditions for the immunity of carp are 348.1?354.5 g kg^?1 protein at 18°C, 352.3?364.9 g kg^?1 at 23°C and 360.2?364.3 g kg^?1 at 28°C, and the optimum temperature for carp is 23°C.     

Effects of dietary folic acid on growth,antioxidant capacity,non‐specific immune response and disease resistance of juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853)

An 8‐week study was conducted to determine folic acid requirement and its effect on antioxidant capacity and immunity in juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853), followed by a challenge assay with the pathogen Aeromonas hydrophila for 2 weeks. Folic acid was added to a basal diet at seven levels (0, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0 mg folic acid kg^?1 diet), and a diet free of folic acid and vitamin B₁₂ was also included as a control. Crabs were fed twice daily in 32 tanks with 7.76–8.17 mg oxygen L^?1, 25.0–31.0 °C and 7.5–8.3 pH. Growth and feed efficiency were significantly greater in crabs fed ≥2.0 mg folic acid kg^?1, but not significantly different between crabs fed diets >2.0 mg folic acid. The superoxide dismutase activity and glutathione S‐transferase activity were highest in crabs fed ≥2.0 mg folic acid kg^?1, followed by those fed 0.5 and 1.0 mg folic acid kg^?1, and the control diet. The malondialdehyde content was highest in crabs fed the control diet, followed by those fed 0 mg folic acid kg^?1, and the lowest value occurred in those fed ≥0.5 mg folic acid kg^?1. Phenoloxidase activity and total haemocytes were significantly higher in crabs fed ≥2.0 mg folic acid kg^?1 than other diets. Crabs fed 2.0 mg folic acid kg^?1 had the highest lysozyme, acid phosphatase and alkaline phosphatase activities but the lowest cumulative mortality. The optimum dietary folic acid requirement by E. sinensis was estimated at 2.29–2.90 mg kg^?1 diet.     

The effect of dietary methionine on growth,antioxidant capacity,innate immune response and disease resistance of juvenile yellow catfish (Pelteobagrus fulvidraco)

An 11‐week feeding trial was conducted to evaluate the effect of dietary methionine on the growth, antioxidant status, innate immune response and disease resistance to Aeromonas hydrophila of juvenile yellow catfish. Six isonitrogenous and isolipidic practical diets were formulated to contain different graded methionine levels ranging from 6.1 to 16.4 g kg^?1 of dry weight. The results indicated that growth performance and feed utilization were significantly influenced by the dietary methionine levels; fish fed the diet containing 6.1 g kg^?1 methionine level had lower specific growth rate, percentage weight gain (PWG), feed efficiency and protein efficiency ratio than those fed the other diets (P < 0.05). Fish fed the diet containing 16.4 g kg^?1 methionine level had lowest protein contents in whole body and muscle among all treatments. Triacylglycerols, cholesterol, aspartate aminotransferase, alanine aminotransferase and haemoglobin (Hb) in plasma or whole blood were significantly affected by dietary methionine levels. Fish fed the diet containing 6.1 g kg^?1 methionine level had higher superoxide dismutase, glutathione peroxidase activities and malondialdehyde values than those fed other diets. Fish fed diets containing 9.7 and 11.8 g kg^?1 methionine levels had higher lysozyme activity, total immune globulin, phagocytic activity and respiratory burst than those fed other diets. The lowest survival after A. hydrophila challenge was observed in fish fed a diet containing 6.1 g kg^?1 methionine. Quadratic regression analysis of PWG against dietary methionine levels indicated that the optimal dietary methionine requirement for the maximum growth of juvenile yellow catfish was estimated to be 11.5 g kg^?1 of the diet in the presence of 4.0 g kg^?1 cystine (corresponding to 23.5 g kg^?1 of dietary protein on a dry weight basis).     

A new potential therapeutic remedy against Aeromonas hydrophila infection in rainbow trout (Oncorhynchus mykiss) using tetra,Cotinus coggygria

Different antibiotic‐based drugs are being used for the treatment of Aeromonas hydrophila infection in rainbow trout, and several studies emphasize the use of medicinal plants as immunostimulants for prophylactic measure against Aeromoniasis disease. However, therapeutic effects of aqueous methanolic extracts of tetra (Cotinus coggygria) against A. hydrophila in rainbow trout were not investigated. Four different concentrations of tetra extract (0 [control], 4, 8 and 12 mg/100 µl) and also two different positive control groups (florfenicol and doxycycline antibiotics) were administered orally using feeding needles to individual rainbow trout, Oncorhynchus mykiss of all experimental groups twice a day after intramuscular inoculation of A. hydrophila. The study period was for 10 days. On 0th, 3rd, 7th and 10th day, blood and tissues were collected from the fish and changes in humoral immune responses, haematology and immune‐related gene expressions were determined. In the study, superoxide radical production was decreased generally in all experimental groups except in 12 mg tetra and florfenicol treatments compared to control (p < .05). Lysozyme activity was generally decreased (p < .05), or no differences were observed in all experimental groups compared to the control. Myeloperoxidase activity was significantly increased in florfenicol‐treated fish group on 7th day (p < .05). Generally, myeloperoxidase activity showed an increase in almost all tetra‐treated groups. Haematological parameters increased but were not significantly high enough in treatments. Almost all immune‐related gene expressions were significantly enhanced on 3rd and 10th day of the study. Survival rate of 53.33% was found in control group. There were no significant differences in survival between control and 4 mg tetra‐treated group (p > .05). All the other groups' survival rate was significantly increased compared to control. The highest survival rate was found in florfenicol group (80%). In 12 mg tetra‐, doxycycline‐ and 8 mg tetra‐treated groups, survival rate was recorded as 74.44%, 70% and 70%, respectively. Our results suggest that tetra methanolic extract is an effective therapeutic remedy against A. hydrophila infection in rainbow trout at the dose of 24 mg/32.34 g body weight/day.