Dietary administration of bovine lactoferrin influences the immune ability of the giant freshwater prawn Macrobrachium rosenbergii (de Man) and its resistance against Aeromonas hydrophila infection and nitrite stress

Haemocyte count, phenoloxidase activity, agglutinin levels, total protein content, bacterial clearance efficiency, resistance to the pathogen Aeromonas hydrophila and nitrite stress were measured in the giant freshwater inter-moult sub-adult prawn Macrobrachium rosenbergii (15-20 g) which had been fed diets containing bovine lactoferrin (Lf) at 50, 100, 200mg kg(-1) feed for 7 or 14 days. M. rosenbergii fed a diet containing 100mg Lf kg(-1) diet for 7 days showed significant (P<0.05) increase in total protein levels, agglutination titres against bacteria A. hydrophila and rabbit RBC, phenoloxidase activity, bacterial clearance (as observed through reduced number of circulating bacteria) as well as survival against A. hydrophila challenge. Increased bacterial clearance was also noticed in prawns fed Lf at 50 or 200mg kg(-1) for 14 days compared to control. Feeding of Lf at 50mg kg(-1) diet for 7 or 14 days was able to enhance only PO activity and reduce percent mortality against A. hydrophila challenge compared to its control. Total haemocyte count was higher in the lowest dose of Lf feeding, i.e. 50mg kg(-1) for 7 days. However, there was no significant alteration in the differential haemocyte population with respect to graded levels of Lf feeding for 7 or 14 days. A notable reduction in mortality percent after 120 h of nitrite stress was observed in prawn fed Lf at 100mg kg(-1) diet for 14 days. On the contrary, feeding of the highest dose of Lf, i.e. 200mg kg(-1) diet for 14 days failed to stimulate most of the innate immune parameters or reduce the percent mortality against A. hydrophila challenge or nitrite stress. It is therefore concluded that administration of Lf in the diet at 100mg kg(-1) for 7 days could enhance the immune ability of M. rosenbergii and increase its resistance to A. hydrophila infection or nitrite stress.     

Effects of polyherbal formulation 'ImmuPlus' on immunity and disease resistance of Indian major carp, Labeo rohita at different stages of growth

A series of experiments were performed to determine the impact of polyherbal immunomodulatory formulation 'ImmuPlus' (AquaImmu) on growth, immunity and disease resistance of rohu (Labeo rohita), one of the Indian major carp at different stages of growth. Rohu larvae were fed on plankton, ImmuPlus-mixed compound feed, and plankton plus ImmuPlus-mixed compound feed (ImmuPlus added at three dose levels of 0.25, 0.50, and 0.75 g/kg feed) from 4th day of hatching to 14th day. ImmuPlus-mixed diets enhanced growth of larvae, survival and disease resistance against Aeromonas hydrophila challenge, compared to only plankton-fed group. In two other experiments, advanced rohu larvae and fingerlings were fed with ImmuPlus-mixed compound feed (at 0, 0.5, 1.0 and 2.0 g/kg) for 15, 30 and 45 days. At the end of 45 days for advanced larvae and 30 days for fingerlings, the fish fed with ImmuPlus at 1.0 g/kg level showed significantly higher growth and disease resistance against A. hydrophila challenge. In a separate experiment, juveniles of rohu were fed with 1 g/kg of ImmuPlus incorporated feed for 15 and 30 days. At the end of the trial, the ImmuPlus fed fish showed enhanced non-specific immunity (as measured through nitroblue tetrazolium reduction assay, serum lysozyme activity, serum haemolysin titre and resistance against A. hydrophila challenge in non-vaccinated fish as well as specific immunity levels (as measured through bacterial agglutination titre against A. hydrophila in vaccinated fish). Incorporation of ImmuPlus at 1 g/kg level in the diet of rohu may be beneficial for enhancing disease resistance.     

Effectiveness of bivalent vaccines against Aeromonas hydrophila and Lactococcus garvieae infections in rainbow trout Oncorhynchus mykiss (Walbaum)

Lactococcus garvieae and Aeromonas hydrophila are bacterial pathogens affecting salmonids and other fish species and cause of heavy losses in aquaculture. Diseases caused by these bacteria can be controlled satisfactory by immunization using monovalent vaccines. In this study, the protective efficacy of two bivalent vaccines against L. garvieae and A. hydrophila was evaluated in rainbow trout (Oncorhynchus mykiss). Bivalent formulations, containing formalin-inactivated bacteria, were prepared as an aqueous bacterin and as an adjuvanted vaccine using montanide ISA-763. Protection against L. garvieae and A. hydrophila was tested at day 30 and 90 post-vaccination. High levels of protection were achieved for the aqueous and adjuvanted bivalent vaccines against L. garvieae (RPS of 100% and 95.3%) and A. hydrophila (RPS of 100% and 95.3%) at day 30 post-vaccination. Significant differences (p < 0.05) were found between the RPS at days 30 and 90 post-immunization with a decrease in the protection levels for the aqueous bivalent vaccine against L. garvieae (RPS 76.2%) and A. hydrophila (RPS 85%), but not for the adjuvanted vaccine (RPS of 90% against L. garvieae and 95% against A. hydrophila). In addition, high antibody levels were observed in the vaccinated fish at day 15 post-immunization using both vaccines. Our results demonstrate that these bivalent vaccines can effectively protect rainbow trout against L. garvieae and A. hydrophila and could offer an appropriate strategy to prevent these infections in rainbow trout farms.     

Dietary supplementation with Cynodon dactylon (L.) enhances innate immunity and disease resistance of Indian major carp, Catla catla (Ham.)

Indian major carp (Catla catla) was subjected to study the immunostimulatory effects when the grass Cynodon dactylon(L) ethanolic extract administrated as feed supplement. C. catla was fed with 0% (Control), 0.05% (group I), 0.5% (group II) and 5% (group III) extract provided for 60 days. Blood samples were collected at every 10 days of interval up to 60 days for analyzing the non-specific humoral (lysozyme activity, antiprotease activity and haemolytic complement) and cellular (production of reactive oxygen and nitrogen species, myeloperoxidase activity) immune response study. The results indicate that C. dactylon ethanolic extract administered as feed supplement significantly (P < 0.05) enhanced most of the non-specific immune parameters tested. Among the experimental diet groups, significantly increased response of non-specific immunity was seen in group III (5%). Disease resistant analysis against Aeromonas hydrophila was performed in control group and plant extract treated fish for 7, 14, 21 and 28 days. Relative percent survival rate (RPS) was observed in treated samples, which is directly proportional to concentration of the extract. Additionally, electron microscopic studies and gelatin zymography for Matrix Metalo Proteinase (MMPs) were examined in spleen at 7th and 28th days of feeding. Administration of C. dactylon mixed diet delayed the lymphocyte destruction with positive ultrastructural changes. An induced stress (A. hydrophila infection) was observed by using MMPs expression, which was reduced in the experimental diet groups than the control. All these experimental results prove that C. dactylon ethanolic extract enhances the immunity of Catla fish.     

Use of bacterial lipopolysaccharide (LPS) as an immunostimulant for the control of Aeromonas hydrophila infections in rainbow trout Oncorhynchus mykiss (Walbaum)

Aims: To determine the effect of lipopolysaccharide (LPS) for the prevention of infection by Aeromonas hydrophila in rainbow trout (Oncorhynchus mykiss Walbaum) fingerlings. Methods and Results: Rainbow trout fingerlings were fed with 0 mg (= controls), 1·875 mg, 3·75 mg, 7·5 mg and 15 mg of LPS per 100 g of commercial feed for 14 days before experimental challenge with A. hydrophila. The results revealed a reduction in mortalities to 5% in the two lowest doses and 15% in the group, which received 15 mg LPS per 100 g of feed, compared with 45% mortalities in the control. LPS exerted a powerful oxidative burst effect and was a potent mediator of phagocytic, lysozyme, bactericidal and antiprotease activities and total protein. However, whereas there were increases in specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) in LPS‐treated fish, the data were not significantly (P > 0·05) different. Conclusions: LPS was effective at preventing disease caused by A. hydrophila and in stimulating the innate immune response of rainbow trout. Significance and Impact of the Study: The results of this study highlight the role of LPS in fish disease control.     

Dietary Korean mistletoe enhances cellular non-specific immune responses and survival of Japanese eel (Anguilla japonica)

The present study was performed to investigate the immunostimulatory effects of Korean mistletoe extract (KM-110; Viscum album Coloratum) on the non-specific immune response and protection against Aeromonas hydrophila infection in Japanese eel (Anguilla japonica). Eels were fed under 4 regimes, 0%, 0.1%, 0.5% and 1.0% KM-110 mixed diet. On day 14 after feeding, 15 fish from each group were injected i.p. with live A. hydrophila (3 x 10(6)CFU) and the remaining unchallenged fish from each group were used to study the innate immune response. On 14 days post-infection, the total survival rates were 26.6% in control, and 33.3%, 66.6% and 80% in 0.1%, 0.5% and 1% KM-110-treated groups, respectively. The maximum lysozyme activity was observed in the 1% KM-110-treated group. There was no significant difference of lysozyme activity between 0.1% and 0.5% KM-110 group. Superoxide anion (O(2)(-)) production was significantly (p<0.05) augmented in the 0.5% and 1% KM-110 groups compared to the control and 0.1% KM-110 group. No significant difference of (O(2)(-) production was found between 0.5% and 1% KM-110 group. Likewise, there was a significant increase in phagocytic activity in the 0.5% KM-110 group compared with the 0.1% group (p<0.05), but no significant difference between the 0.5% and the 1% KM-110 group indicating that 0.5% KM-110 concentration is suitable for stimulating maximum phagocytic activity resulting in a high amount of ROI production. Considering the present results, KM-110 could be utilized as a promising immunostimulating substance for a diet in aquaculture.     

Effect of Mangifera indica kernel as a feed additive on immunity and resistance to Aeromonas hydrophila in Labeo rohita fingerlings

The study evaluated the efficacy of dietary doses of Mangifera indica (mango) kernel on the immune response and disease resistance of Labeo rohita fingerlings against the bacterial pathogen Aeromonas hydrophila infections in. L. rohita fingerlings fed diet containing 0 (Control), 1g, 5 g, 10 g mango kernel kg(-1) dry diet for 60 days. Biochemical (serum total protein, albumin, globulin, albumin:globulin ratio, blood glucose), haematological (WBC, RBC, haemoglobin content) and immunological (superoxide anion production, lysozyme, serum bactericidal activity) parameters of fish were examined at 20, 40 and 60 days of feeding. Fish were challenged with A. hydrophila 60 days post feeding and mortalities were recorded over 10 days post-infection. The results demonstrate that fish fed with mango kernel showed enhanced superoxide anion production, lysozyme, serum bactericidal, serum protein, albumin (P<0.05) compared with the control group. The mortality (%) was recorded up to 10 th day post-challenge. Less survivability was observed in control group (50%) up to day 10 after infection. The survivability was higher in experimental diets. The group fed 5 g kernel kg(-1) dry diet showed highest percentage survival (98%). These results indicate that mango kernel stimulates the immunity and makes L. rohita more resistant to A. hydrophila infection.     

Oral administration of Eclipta alba leaf aqueous extract enhances the non-specific immune responses and disease resistance of Oreochromis mossambicus

Immunostimulatory effects of the oral administration of the medicinal plant, Eclipta alba leaf extracts was studied in tilapia, Oreochromis mossambicus. For this purpose, fish were fed for 1, 2 or 3 weeks with diets containing E. alba leaf aqueous extract at 0, 0.01, 0.1 or 1% levels. After each week, non-specific humoral (lysozyme, antiprotease and complement) and cellular (myeloperoxidase content, production of reactive oxygen and nitrogen species) responses and disease resistance against Aeromonas hydrophila were determined. The results indicated that E. alba aqueous extract administered as feed supplement significantly enhanced most of the non-specific immune parameters tested. Among the humoral responses, lysozyme activity significantly increased after feeding with aqueous extract for 1, 2 or 3 weeks. No significant modulation was noticed in all the cellular responses tested after 3 weeks of feeding, while reactive oxygen species production and myeloperoxidase content showed significant enhancement after 1 week of feeding with aqueous extract. When challenged with A. hydrophila after 1, 2 or 3 weeks of feeding, the percentage mortality was significantly reduced in the treated fish. The highest dose of 1% gave better protection than the other doses with the relative percentage survival (RPS) values of 64, 75 and 32 after feeding for 1, 2 and 3 weeks respectively. The results indicate that dietary intake of E. alba aqueous leaf extract enhances the non-specific immune responses and disease resistance of O. mossambicus against A. hydrophila.     

Evaluation of biofilm of Aeromonas hydrophila for oral vaccination of Clarias batrachus--a carnivore model

Biofilm of Aeromonas hydrophila was evaluated for oral vaccination of walking catfish (Clarias batrachus L.). Fish were fed with fish paste incorporating biofilm (BF) or free cells (FC) of A. hydrophila for 20 days and monitored for serum antibody production up to 60 days post-vaccination. Serum agglutinating antibody titre and relative percent survival (RPS) following challenge were found to be significantly higher in catfish fed with BF vaccine compared to that with FC.     

Chinese herbs (Astragalus radix and Ganoderma lucidum) enhance immune response of carp, Cyprinus carpio, and protection against Aeromonas hydrophila

The effect of Chinese herbs (Astragalus radix and Ganoderma lucidum) on immune response of carp was investigated. Fish were fed diets containing Astragalus (0.5%), Ganoderma (0.5%) and combination of two herbs (Astragalus 0.5% and Ganoderma 0.5%) for 5 weeks. Other groups of fish were vaccinated (i.p.) against Aeromonas hydrophila/Aeromonas salmonicida (Shering Plough, Essex, U.K.) at the beginning of the experiment and fed the same diets as described above. Control fish (negative control) and fish vaccinated only (positive control) were fed basal diets without supplements of herbs. The respiratory burst activity, phagocytosis, lysozyme activity and circulatory antibody titres in plasma were monitored. Following 5 weeks after feeding, fish were infected with A. hydrophila and mortalities were recorded. The results of this study showed that feeding non-vaccinated and vaccinated carp with combination of Astragalus and Ganoderma stimulated respiratory burst activity, phagocytosis of phagocytic cells in blood and lysozyme and circulatory antibody titres in plasma in vaccinated carp. Fish challenged with A. hydrophila had variable survival. The best survival (60%) was in vaccinated group fed with both herbs, while almost 90% of control fish (negative control) and 60% of fish vaccinated only (positive control) died.     

Effects of dietary supplementation of potential probiotic Pseudomonas aeruginosa VSG-2 on the innate immunity and disease resistance of tropical freshwater fish, Labeo rohita

The effects of dietary Pseudomonas aeruginosa VSG-2 supplementation on innate immunity and protection against Aeromonas hydrophila infection were evaluated in Labeo rohita. Fish were fed for 60 days with control diet or 3 experimental diets containing P. aeruginosa VSG-2 at 10(5), 10(7), and 10(9) cfu g(-l), respectively. Various innate immune parameters were examined at 30 and 60 days post-feeding. Fish were challenged with A. hydrophila 60 days post-feeding and mortalities were recorded over 10 days post-infection. Dietary supplementation of P. aeruginosa VSG-2 significantly increased serum lysozyme and alternative complement pathway (ACP) activities, phagocytosis, and respiratory burst activity in head kidney macrophages of L. rohita throughout the experimental period. Superoxide dismutase (SOD) activity significantly increased after 60 days in the groups fed diets containing 10(7) and 10(9) cfu g(-1) P aeruginosa. Serum IgM levels were significantly higher in the treatment groups than in the control group after 30 days of feeding; however, the opposite result was observed at 60 days. Moreover, fish fed diets containing 10(7) and 10(9) cfu g(-1)P. aeruginosa had significantly higher post-challenge survival rates against A. hydrophila infection. Further, P. aeruginosa VSG-2 was found to be safe for mammals. These results indicate that dietary P. aeruginosa VSG-2 supplementation at 10(7) cfu g(-1) can effectively improve innate immunity and disease resistance in L. rohita.     

The effect of mistletoe, Viscum album coloratum, extract on innate immune response of Nile tilapia (Oreochromis niloticus)

The purpose of the present study was to evaluate the effect of dietary mistletoe extracts on non-specific immune response and disease resistance of Nile tilapia (Oreochromis niloticus) against Aeromonas hydrophila infection. Tilapia fingerlings were fed with a diet containing 0 mg as a control, 10 mg, 50 mg, and 200 mg mistletoe powder kg(-1) dry diet for 80 days. The immunological parameters, respiratory burst activity, lysozyme activity, alternative complement haemolysis activity (ACH(50)), and phagocytic activity of fish were investigated following 20, 40 and 80 days of feeding. Fish were challenged with A. hydrophila on 80 days after feeding and mortalities were checked over 10 days post-infection. The results show that fish fed with mistletoe extract exhibited an increase in activity in all immunological parameters (P < 0.05) compared to the control group depending on feeding periods and doses of mistletoe. Following challenge with A. hydrophila, 42% less survivability was observed in the control group than in other experimental diet groups. The highest survival rate (83%) was shown in the group fed with a 50 mg mistletoe kg(-1) diet. The results suggest that mistletoe enables tilapia to promote immunity and be more resistant to A. hydrophila infection.     

Dietary administration of nucleotides to enhance growth, humoral immune responses, and disease resistance of the rainbow trout (Oncorhynchus mykiss) fingerlings

A feeding study was conducted to determine the effect of dietary nucleotides (NT) on growth performance, immune responses and resistance of rainbow trout fingerlings to Streptococcus iniae. A basal diet supplemented with 0 (control), 0.5, 1, 1.5 and 2 g NT kg(-1) to formulate five experimental diets. Each diet was randomly allocated to triplicate groups of fish with initial average weight of approximately 23 g. After 8 weeks of feeding trial, fish fed diets with 1.5-2 g NT kg(-1) had the highest final weight and SGR, followed by groups fed the diets with 0.5-1 g NT kg(-1), and lowest in fish fed the NT-free control diet. The feed conversion ratio (FCR) was better when the fish were fed diet with 2 g NT kg(-1). The ACH(50) level and lysozyme activity in serum were found to be significantly (P < 0.05) greater in fish fed nucleotides at 1.5-2 g kg(-1). The fish fed with 2 g NT kg(-1) had higher IgM level. The challenge experiment showed that relative percent survival (RPS) increased significantly (P < 0.05) with increasing levels of nucleotides from 0.5 to 2 g kg(-1) and was lowest in the control group. We therefore recommend dietary nucleotide administration at 1.5-2 g kg(-1) to promote growth and enhance immunity and resistance against S. iniae.     

Haemato-immunological and growth response of mirror carp (Cyprinus carpio) fed a tropical earthworm meal in experimental diets

An investigation was conducted to evaluate the effect of feeding a tropical earthworm meal (Perionyx escavatus) on the haemato-immunological response and growth performance of mirror carp (Cyprinus carpio). Fish were fed diets for a total of 88 days, fishmeal served as the main protein source in the control diet. Two remaining diets consisted of fishmeal fixed at 33.65% provision of protein and the remaining 66.35% protein was provided by soybean meal (SBM diet) or P. excavatus meal (EW diet). Compared to control and SBM fed fish (7.69 ± 0.28 and 5.92 ± 0.31 g/dl, respectively), a significant increase in haemoglobin was measured in EW fed fish (9.57 ± 0.24 g/dl). Consequently significant elevations were also observed in mean corpuscular haemoglobin (MCH; 79.13 ± 4.59 pg) and mean corpuscular haemoglobin concentration (MCHC; 22.69 ± 0.54 pg) in EW fed fish. On the contrary, compared to control and SBM fed carp total leukocyte levels (2.72 ± 0.17 and 3.10 ± 0.17 × 10(4)/mm(3), respectively) were significantly decreased in the EW group (2.15 ± 0.14 × 10(4)/mm(3)). Moreover at day 14 and 21 post immunisation with bacterin isolated from Aeromonas hydrophila fish fed the EW diet displayed a significant reduction in respiratory burst activity (RBA) compared to control and SBM fed fish. After 60 days of feeding, fish fed EW diet showed a significant elevation in final body weight compared to fish fed a fishmeal based diet (control treatment) and fish fed a soybean meal based diet. Similar improvements were observed in feed utilisation efficiency. The present study shows that feeding P. excavatus meal to mirror carp decreases some aspects of the innate immune response, but at the same time gives rise to significant enhancement of growth and feed utilisation efficiency.     

Dietary microbial levan enhances cellular non-specific immunity and survival of common carp (Cyprinus carpio) juveniles

A preliminary study with a 75days feeding trial was conducted to study the immunomodulatory effect of microbial levan on Cyprinus carpio juveniles. Five purified isonitrogenous and isocaloric diets with graded levels of levan, namely (T(1)) 0.1% levan, (T(2)) 0.2% levan, (T(3)) 0.5% levan, (T(4)) 1.0% levan, and a control group without levan were fed to five groups of fishes in triplicate. The total erythrocyte count and haemoglobin content was significantly (p<0.05) enhanced in the T(3) group, though the total leucocyte counts, total protein and A/G ratio did not show any significant difference (p>0.05) when compared with the control group. The respiratory burst activity (NBT) of blood phagocytes and lysozyme activity was also highest in T(3) group. The relative survival percentage after challenge with Aeromonas hydrophila was highest (100%) in the T(3) group followed by 83.33% and 66.67% in the T(2) and T(4) groups, respectively. This suggests that microbial levan at 0.5% can be used as a dietary immunostimulant for C. carpio juveniles. This is the first report on microbial levan having an immunomodulatory effect on C. carpio.     

甘露寡糖对异育银鲫生长性能、免疫及HSP70基因表达的影响

为探讨甘露寡糖(MOS)对异育银鲫生长、免疫、肠道组织结构及抗病力的影响,试验选取360尾异育银鲫[初均重(16.19±0.03)g],随机分成5组、每组3个重复,在日粮中添加不同浓度甘露寡糖(0、60、120、240、480 mg/kg),连续投喂80d,并于第80天时进行嗜水气单胞菌感染,测定异育银鲫生长、免疫、肠道结构等指标及异育银鲫抗嗜水气单胞菌感染的能力。试验结果表明,无论投喂50d,还是80d,甘露寡糖对鱼体的生长指标(特定生长率、增重率、蛋白质效率、饵料系数)均没有显著影响(P>0.05);投喂50d,与对照组比,甘露寡糖能显著提高血清球蛋白浓度(P<0.05);投喂80d后,与对照组比,240、480 mg/kg甘露寡糖组能显著提高碱性磷酸酶活性,甘露寡糖组能显著提高血清球蛋白浓度(P<0.05),480 mg/kg甘露寡糖组能显著提高血清总抗氧化能力,120、240 mg/kg甘露寡糖组能显著提高肠褶皱襞长(P<0.05),对皱襞间质宽、黏膜下层宽没有显著影响(P>0.05),肌层宽随着MOS的添加有增加趋势(P>0.05);嗜水气单胞菌感染后,与对照组比,240、480 mg/kg甘露寡糖组成活率提高了22.6%,免疫保护率达45.4%。日粮中添加甘露寡糖组对鱼体肝脏HSP70基因表达没有显著影响(P>0.05)。因此,添加240、480 mg/kg甘露寡糖能提高鱼体的免疫能力,增强鱼体抗病原菌感染能力。     

Dietary sodium alginate administration affects fingerling growth and resistance to Streptococcus sp. and iridovirus, and juvenile non-specific immune responses of the orange-spotted grouper, Epinephelus coioides

The percent weight gain (PWG) and feeding efficiency (FE) of fingerling orange-spotted grouper, Epinephelus coioides, fed diets containing sodium alginate at 1.0 and 2.0 g kg(-1) were calculated on the 2nd, 4th, 6th, and 8th weeks after feeding. Survival rates of the fingerling grouper against Streptococcus sp. and an iridovirus, and non-specific immune parameters such as alternative complement activity (ACH50), lysozyme activity, natural haemagglutination activity, respiratory bursts, superoxide dismutase (SOD) activity, and phagocytic activity of juvenile grouper were also determined when the fish were fed diets containing sodium alginate at 0.5, 1.0, or 2.0 g kg(-1). The PWG and FE of fish were better when the fish were fed diets containing sodium alginate at 1.0, and 1.0 and 2.0 g kg(-1), respectively. The PWG and FE of fish fed the 0, 1.0 and 2.0 g kg(-1) sodium alginate-containing diets after 8 weeks were 271.0%, 454.4% and 327.8%, and 0.61, 0.72 and 0.68, respectively. Fish fed a diet containing sodium alginate at the level of 2.0 g kg(-1) had a significantly higher survival rate than those fed the control diet after challenge with Streptococcus sp. and an iridovirus causing an increase of survival rate by 25.0% and 16.7%, respectively, compared to the control group. The ACH(50) level of fish fed the sodium alginate-containing diets at 2.0 g kg(-1) was significantly higher than those fed the 1.0 g kg(-1) sodium alginate diet and control diet after 12 days, and had increased to 1.9-fold, compared to those fed the control diet. The lysozyme activity, phagocytic activity, respiratory bursts, and SOD level of fish fed the sodium alginate-containing diets at 1.0 and 2.0 g kg(-1) were significantly higher than those fed the control diet after 12 days, and had increased to 1.97- and 1.68-fold, 1.35- and 1.50-fold, 1.63- and 1.81-fold, and 1.23- and 1.31-fold, respectively, compared to those fed the control diet. We therefore recommend dietary sodium alginate administration at 1.0 and 2.0 g kg(-1), respectively, to promote growth and enhance immunity and resistance against Streptococcus sp. and an iridovirus.     

The auxotrophic aroA mutant of Aeromonas hydrophila as a live attenuated vaccine against A. salmonicida infections in rainbow trout (Oncorhynchus mykiss)

An auxotrophic aroA mutant of the Aeromonas hydrophila AG2 strain is a live attenuated vaccine against A. hydrophila infection in rainbow trout (Oncorhynchus mykiss). The protection conferred by the live attenuated vaccine against A. salmonicida strains is reported here, and several parameters of the specific and non-specific immune response in vaccinated trout were characterised. Vaccination with a dose of 10(7)cells/fish of the aroA mutant elicited significant protection against the Hooke and DK30 strains of A. salmonicida (relative percent survival RPS >60%). This cross-protection correlated moderately with the activation of the humoral and cellular specific immune responses, which show cross-reactivity against antigens shared by the two bacterial species, and a moderate increase in the lysozyme and antiprotease activities in the serum of vaccinated trout.     

Immunomodulatory effects of decaffeinated green tea (Camellia sinensis) on the immune system of rainbow trout (Oncorhynchus mykiss)

In order to study the immunomodulatory effects of decaffeinated green tea extract on rainbow trout, a study with a 30-day feeding trial was conducted. Commercial diets with graded levels of decaffeinated green tea extract, 20 mg (T1), 100 mg (T2), 500 mg (T3) per kg feed were prepared. 120 rainbow trout (35 ± 3 g) were randomly assigned to 4 groups in triplicates and fed one of the 3 experimental diets formulated or control diet. After feeding trial, 12 fish from each group were sampled for analysis of some immunological parameters. Remaining fish were injected with 0.5 ml of chicken red blood cell (C-RBC) suspension (2%) intraperitoneally on days 5 and 15 after feeding trial. Results of the current study showed that the inclusion of 20 mg kg-1 green tea (T1) in fish diet enhanced the serum bactericidal activity against Yersinia ruckeri, while significant elevation of lysozyme activity was shown in T2 group. Anti-trypsin activity due to α1-antiprotease was significantly higher in T1 and T2 groups while peroxidase content showed significant increase in all treatment groups compared to control group. Hemagglutination antibody titer against C-RBC was significantly higher in fish administered with 100 mg kg(-1) green tea (T2). Our findings showed that decaffeinated green tea in lower doses of administration could be optimum to enhance the immunity of rainbow trout.     

Pre- and post-challenge immuno-haematological changes in Labeo rohita juveniles fed gelatinised or non-gelatinised carbohydrate with n-3 PUFA

The combined effect of dietary carbohydrate type and n-3 PUFA (EPA+DHA) on pre- and post-challenge haemato-immunological responses in Labeo rohita juveniles was studied. Fish were fed for 67days with six different test diets containing either gelatinised (G) or non-gelatinised (NG) corn (43%) with three levels of n-3 PUFA (0.5%, 1.0% and 2.0%). During the pre-challenge period, significantly higher (P<0.05) NBT, serum lysozyme activity, total protein and globulin content was recorded in the NG carbohydrate fed groups. Highest NBT value was recorded in the groups fed with 1.0% n-3 PUFA, whereas the highest serum lysozyme activity (P<0.05) was recorded at either 0.5% or 2.0% n-3 PUFA fed groups in both the pre- and post-challenge period. Feeding of NG corn significantly increased the total leucocyte count, lysozyme activity, A/G ratio and decreased the total erythrocyte count, haemoglobin, serum total protein and globulin content of L. rohita juveniles during the post-challenge period. Similarly, feeding of n-3 PUFA at any level significantly increased the immunological parameters like lysozyme activity or A/G ratio, whereas total leukocyte count increased due to feeding of either 0.5% or 1.0% n-3 PUFA. The NBT and albumin values remained similar in both the pre- and post-challenge period. After challenge with Aeromonas hydrophila, the highest survival was recorded in the NG carbohydrate fed groups, whereas the lowest survival was recorded in the highest level of n-3 PUFA fed group irrespective of dietary carbohydrate type. Thus, a high level of G carbohydrate as well as n-3 PUFA is found to be immunosuppressive in L. rohita juveniles. NG carbohydrate supplemented with 1.0% n-3 PUFA is found to be optimum to enhance the immunity in L. rohita juveniles.