Immunomodulation of Labeo rohita juveniles due to dietary gelatinized and non-gelatinized starch

A 60 days experiment was conducted to study the effect of dietary gelatinized (G) and non-gelatinized (NG) starch on immunomodulation of Labeo rohita juveniles. Two hundred and thirty four juveniles (av. wt. 2.53+/-0.04) were randomly distributed in six treatment groups with each of three replicates. Six semi-purified diets containing NG and G corn starch, each at six levels of inclusion (0, 20, 40, 60, 80, 100) were prepared viz., T(1) (100% NG, 0% G starch), T(2) (80% NG, 20% G starch), T(3) (60% NG, 40% G starch), T(4) (40% NG, 60% G starch), T(5) (20% NG, 80% G starch) and T(6) (0% NG, 100% G starch). After a feeding period of 60 days, the juveniles were challenged with Aeromonas hydrophila to study their immunomodulation due to feeding of G and NG starch. RBC and haemoglobin content were significantly (P<0.05) reduced due to bacterial challenge, but dietary starch (G/NG starch) had no effect on it. G:NG starch ratio in the feed had significant effect on total leukocyte count during pre- and post-challenge periods. The leukocyte count concomitantly increased with the increased level of G starch in the diet. Highest albumin/globulin (A/G) ratio was recorded in T6 group (100% G starch) and lowest in T1 group (100% NG starch) group followed by T2 group both in pre- and post-challenge periods. NBT, lysozyme activity, total protein and globulin content were highest in T2 group (80% NG, 20% G starch) both in pre- and post-challenge periods. After challenge with A. hydrophila, the highest survival was recorded in T2 group, whereas lowest survival was recorded in T6 group. Conclusively high level of G starch was found to be immunosuppressive in Labeo rohita juveniles and NG:G starch ratio of 80:20 seems to be optimum for promoting growth and protecting immunity in L. rohita juveniles.     

Haemato-immunological responses to dietary yeast RNA, omega-3 fatty acid and beta-carotene in Catla catla juveniles

A preliminary study with 60 days feeding was conducted to study the immunomodulatory role of different immunostimulants like beta-carotene, omega-3 fatty acid and yeast-RNA in Catla catla fingerlings. Two hundred and sixty four fingerlings were randomly distributed into eight treatment groups with each of three replicates. Eight isonitrogenous (crude protein 34.12-35.40%) and isocaloric (458.41-461.48 kcal/100g) purified diets were prepared with graded level of beta-carotene, omega-3 fatty acid and yeast-RNA viz., Control (basal diet), T1 (Basal + 1% omega-3 fatty acid), T2 (Basal + 3% omega-3 fatty acid), T3 (Basal + beta-carotene), T4 (T1 + beta-carotene), T5 (T2 + beta-carotene), T6 (Basal + 0.4% yeast-RNA) and T7 (Basal + 0.8% yeast-RNA). The immunomodulatory effects of dietary immunostimulants were studied in terms of respiratory burst activity (NBT) of blood phagocytes, total leukocyte count, serum total protein, serum globulin, A/G ratio (A/G) and serum lysozyme activity. The respiratory burst activity of T7 group was significantly higher (p<0.05) than the other groups. Haemoglobin content, total erythrocyte count and serum albumin content did not vary among the treatment groups, whereas total leukocyte count, serum globulin content and serum lysozyme activity were found to be highest in T7 group. Relative survival percent after challenge with Aeromonas hydrophila was also highest in T7 (88.88%) group followed by T6 (75.06%) and T4 (66.66%) and the lowest in T2 group. It was observed that total leucocyte count, NBT and lysozyme activity of T2 group fed with high omega-3 fatty acid (3%) was less than (p<0.05) its lower counterparts T1 (1%) and control group. Based on the results of the present study, it concludes that supplementation of yeast-RNA at 0.8% registered higher immunological responses in C. catla juveniles. It is also observed that higher supplementation of omega-3 fatty acid (3%) in the diet causes immunosuppression in C. catla juveniles.     

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.     

Enhanced innate immune parameters in Labeo rohita (Ham.) following oral administration of Bacillus subtilis

The present study assessed the use of Bacillus subtilis in fish as a probiotic. The bacterium was administered orally at three different doses 0.5 x 10(7) (T(2)), 1 x 10(7) (T(3)), 1.5 x 10(7) (T(4)) cfu/g feed to Labeo rohita for two weeks. The positive control group (T(1)) and negative control group (T(5,)) were fed feed without B. subtilis for the same period. On the 15th day blood and serum were sampled to determine respiratory burst activity (NBT assay), differential leukocyte counts (DLC) and serum bactericidal activity. Fishes were challenged intraperitoneally with Aeromonas hydrophila O:18 after two weeks in the treatment groups (T(2), T(3) and T(4)) and also in the positive control group(T(1)), while the negative control group (T(5)) was challenged with phosphate buffered saline (PBS, pH 7.2) only. The respiratory burst activity and DLC were assessed on the 3rd day post-challenge. B. subtilis treated fish showed significantly higher (P<0.05) respiratory burst activity and bactericidal activity during the pre-challenge compared with the control groups. The highest respiratory burst activity (0.37+/-0.03) and serum bactericidal activity were recorded in the group (T(4)) fed feed containing B. subtilis at 1.5 x 10(7)cfu/g feed. Granulocyte numbers were significantly higher (P<0.05) in treatment groups in comparison to the control in both the pre- and post-challenge periods. The result suggests that B. subtilis can enhance certain innate immune responses in rohu.     

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.     

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.     

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.     

Production of superoxide anion by head-kidney leucocytes of Indian major carps immunised with bacterins of Aeromonas hydrophila

On contact with micro-organisms or any other antigenic particles which are recognised as phagocytosable, the leucocytes of vertebrates raise their oxygen consumption suddenly (respiratory burst). The consumed oxygen is then converted into reactive oxygen species (ROS). An effort has been made in the present study to estimate the production of superoxide anion, one of the ROS, by the resident as well as activated head-kidney leucocytes of Indian major carps. Activation was accomplished by immunisation with formalin killed (FK) and heat killed (HK) whole cell bacterins of Aeromonas hydrophila. In the ex vivo experiment conducted, activated leucocytes yielded a significant increase in O.D. values for nitroblue tetrazolium (NBT) reduction reaction, reflecting an increase in superoxide anion production, from day 1 post immunisation. Of the three species of Indian major carps immunised, Catla catla showed the greatest production of superoxide anion, followed by Labeo rohita and then by Cirrhinus mrigala. The enhancement of superoxide anion production of leucocytes by immunisation justifies the role of immunisation in the microbicidal defence mechanism of fish.     

Effect of Achyranthes aspera on the immunity and survival of Labeo rohita infected with Aeromonas hydrophila

Achyranthes aspera seed was incorporated in the diets (at 0.01%, 0.1% and 0.5%) of Labeo rohita, rohu fingerlings (3.0+/-0.4 g). After 2 weeks, the fish were immunized with heat-killed Aeromonas hydrophila, and after a further 2 weeks the rohu were experimentally infected with Aeromonas hydrophila (ATCC 49140). After 7 days blood and serum were sampled to determine superoxide anion production, bactericidal activity, lysozyme, serum protein, albumin, globulin, serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) and alkaline phosphatase (ALP). Superoxide anion production, serum bactericidal activity, lysozyme, ALP, serum protein, albumin:globulin ratio (A/G) were enhanced in Achyranthes treated groups compared to the control group. SGOT and SGPT levels were elevated in control group, but in Achyranthes treated groups the levels were similar to the uninfected-control group. Higher cumulative mortalities were observed in the control group (77%) up to day-9 after infection. This gradually decreased with increasing dose of Achyranthes, 66% mortality in 0.01% group, 57% mortality in 0.1% group and 28% mortality in 0.5% group. These results indicate that Achyranthes aspera stimulates immunity and increases resistance to infection in L. rohita.     

Effect of dietary carbohydrate on haematology, respiratory burst activity and histological changes in L. rohita juveniles

A feeding trial was conducted for 60 days to delineate the effect of dietary carbohydrate on the haematology, respiratory burst activity and histology in Labeo rohita juveniles. One hundred and forty four fish (av. wt. 10+/-0.15 g) were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets with either 35% or 28% of crude protein were prepared with different amylase concentrations (0, 50, 100 and 150 mgkg(-1)) and starch type (gelatinised, G/non-gelatinised, NG) designated as T1 (NG, 35% CP, 0 mgkg(-1) amylase), T2 (G, 35% CP, 0 mgkg(-1) amylase), T3 (NG, 28% CP, 50 mgkg(-1) amylase), T4 (NG, 35% CP, 50 mgkg(-1) amylase), T5 (G, 28% CP, 50 mgkg(-1) amylase), T6 (G, 35% CP, 50 mgkg(-1) amylase), T7 (NG, 28% CP, 100 mgkg(-1) amylase), T8 (NG, 35% CP, 100 mgkg(-1) amylase), T9 (G, 28% CP, 100 mgkg(-1) amylase), T10 (G, 35% CP, 100 mgkg(-1) amylase), T11 (NG, 28% CP, 150 mgkg(-1) amylase) and T12 (NG, 35% CP, 150 mgkg(-1) amylase). The fish were acclimatised to the experimental conditions for 15 days during which time the control diet was fed. The blood haemoglobin percentage and RBC count was not significantly different (P>0.05) among the various treatments. Highest WBC count, total plasma protein, serum globulin and respiratory burst activity was found at 50 mgkg(-1) dietary amylase supplementation, whereas no variation (P>0.05) was found at 0, 100 and 150 mgkg(-1) dietary amylase supplementation. There was no difference (P>0.05) in the serum albumin and AG ratio among the experimental groups. Feeding either gelatinised or non-gelatinised carbohydrate did not affect the histological structure of the liver, kidney and intestine except in the T4 and T7 groups. The T4 group showed hyperplasia of the intestine and moderate vacuolation in hepatic cells, whereas the T7 group showed hyperplasia of the intestine. Non-gelatinised carbohydrates (46%) along with supplementation with 50 mgkg(-1) amylase stimulated the immune system in L. rohita juveniles. But supplementation of amylase to the gelatinised carbohydrate had no immunostimulating effect.     

黄连须和小檗碱对草鱼非特异性免疫系统的影响及对嗜水气单胞菌感染的抵抗作用

为了评估黄连须(FRC)和小檗碱(BBR)对草鱼(Ctenopharyngodon idella)的非特异性免疫及对抵抗嗜水气单胞菌感染的影响, 鱼喂食含1.00%、0.50%、0.25%, 0.10%, 0.00%的FRC和0.05%BBR的饲料28d。喂养28d后, 鱼注射嗜水气单胞菌, 记录感染14d后的存活率。检测NBT活性、血清溶菌酶活性、吞噬活性和补体C3水平来评价药物对草鱼的免疫反应。结果表明, 与模型组相比, 喂养饲料含有FRC和BBR的各组提高NBT活性、血清溶菌酶活性、吞噬活性和草鱼补体C3水平。喂食0.50%FRC组感染细菌后的存活率最高, 与模型组比较增加44%。FRC和BBR的体外抗菌活性采用最小抑菌浓度的方法进行了研究, 并显示出较强的抑制作用。结果表明, FRC和BBR可以用作免疫刺激剂以提高草鱼非特异性免疫和对嗜水气单胞菌引起疾病的抵抗。       

Effect of multiple injections of beta-glucan on non-specific immune response and disease resistance in Labeo rohita fingerlings

The purpose of this study was to determine if multiple injections of different dosages of beta-glucan derived from barley would enhance the immune response and disease resistance against infections due to opportunistic pathogens Aeromonas hydrophila and Edwardsiella tarda in Labeo rohita fingerlings. Hence, four different dosages of beta-glucan suspension in phosphate-buffered saline at the rate of 0, 5, 10, 15 mg kg(-1) body weight of fish were injected intraperitoneally to the fingerlings of Labeo rohita at two-week intervals for four times. After every two-week interval different serum biochemical, haematological and immunological parameters of fish were evaluated. At the end of immunostimulation trial of 56 days, fish were divided into four subgroups under each major treatment group for challenge through i.p injection and bath immersion with two pathogens, A. hydrophila and E. tarda. The mortality (%) and agglutinating antibody titre was recoded on 28th day post challenge. Most of the immune parameters such as leucocyte count, phagocytic ratio, phagocytic index, lysozyme activity, complement activity, serum bactericidal activity were significantly (P < 0.05) enhanced on 42 days after three i.p injections of 10 mg of beta-glucan kg(-1) body wt. Challenge study indicated least mortality in the group of fishes injected with medium dose of 10 mg of beta-glucan kg(-1) body wt. four times. Multiple injections of beta-glucan might have maintained the activation of phagocytic cells for a long period which in turn would lead to long-term protection in fishes. Thus, injections of 10 mg of beta-glucan kg(-1) body wt. for three times can be advocated to enhance the immune response of fish species under aquaculture.     

Immunisation of Indian major carps against Aeromonas hydrophila by intraperitoneal injection

The Indian major carps Catla catla, Labeo rohita and Cirrhinus mrigala were immunised against the potent bacterial fish pathogen, Aeromonas hydrophila by the intraperitoneal route, in field conditions. Two different polyvalent antigen preparations namely, whole cell and extracellular products (ECP) were used. Immunisation schedule consisting of a single booster dose given 28 days after priming resulted in a good agglutinating antibody response in the carps. Kinetics of the response were similar in the three carp species with both whole cell and ECP. Upon challenge with virulent strains, relative percent survival as high as 80-90% was recorded. Indian major carps are the most important freshwater species cultured in India and it is essential that they are protected against infections of A. hydrophila, a scourge of freshwater fish worldwide.     

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.     

The immunomodulatory effects of tuftsin on the non-specific immune system of Indian Major carp, Labeo rohita

The purpose of this study was to determine if injections of different dosages of tuftsin would enhance the immune response and disease resistance against the infections due to the opportunistic pathogens Aeromonas hydrophila and Edwardsiella tarda in Labeo rohita fingerlings. Hence, four different dosages of tuftsin in PBS suspension at the rate of 0, 5, 10, 15 mg kg(-1) body weight of fish were injected intraperitoneally to the fingerlings of L. rohita at 2-week intervals for four times. After every 2-week interval, different serum biochemical, haematological and immunological parameters of fish were evaluated. Biochemical and haematological parameters including serum total protein content, albumin content, globulin content, albulin:globulin ratio, glucose content, leucocyte counts etc.; cellular immune parameters including superoxide anion production, phagocytic activities, lymphokine production index etc.; humoral immune parameters including lysozyme activity, complement activity, serum bactericidal activity etc., in the fish were evaluated after every 2-week interval. After 56 days, fish were divided into two subgroups under each major treatment group for challenge with two pathogens A. hydrophila and E. tarda. The mortality (%) and agglutinating antibody titre was recorded on 28th day post challenge. Most of the immune parameters including leucocyte count, phagocytic ratio, phagocytic index, lysozyme activity, complement activity, and serum bactericidal activity were significantly (p相似文献   

The immunosuppressive effect of alpha-permethrin on Indian major carp, rohu (Labeo rohita Ham.)

The immunosuppressive effects of bath exposure to a sub lethal concentration of the synthetic pyrethroid alpha-permethrin (3.05 x 10(-4) mg l(-1)) in the Indian Major carp, Labeo rohita was studied after 45 days' exposure. In some groups, the effects of alpha-permethrin on non-specific defences and serum enzymes of carp were investigated after challenge with Aeromonas hydrophila. Several nonspecific immune responses and serum enzymes were reduced after exposure of alpha-permethrin. Bactericidal activity of rohu serum was reduced significantly in pesticide and bacteria treated fish. The Glutamic Oxaloacetate Transaminase (GOT) and Glutamic Pyruvate Transaminase (GPT) activity were increased in immunosuppressed fish. Blood glucose level was elevated significantly and Hb% was reduced significantly in pesticide and bacteria treated fishes as compared to the negative control.     

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.     

Digestive enzymes and metabolic profile of Labeo rohita fingerlings fed diets with different crude protein levels

Labeo rohita, commonly called rohu is one of the most important fish species for aquaculture in India. Digestive enzyme response and metabolic profile of fingerling L. rohita to different dietary crude protein (CP) levels (viz. 25, 30, 35 and 40%) were studied in an attempt to optimize a practical diet formulation for this species. After 45 days of feeding, activity of digestive enzymes and metabolite concentrations were assayed. Amylase, lipase and alkaline phosphatase (ALP) activities were not influenced by the dietary protein, but proteolytic and acid phosphatase (ACP) activities varied (P<0.05) between the treatments. Proteolytic activity showed a second order polynomial relationship with dietary crude protein (CP) as Y = 0.0734X(2) + 4.937X - 68.37, r(2)=0.97. A positive correlation was observed between dietary CP and amylase (r(2)=0.78). All the metabolites except muscle glucose showed significant change corresponding to the dietary protein levels. Glucose and glycogen levels corresponded to the dietary carbohydrate levels. Muscle and plasma pyruvic acid increased as the crude protein in the diet increased, whereas liver pyruvic acid showed the opposite trend. Muscle protein content was not affected by dietary CP. Protein fractions in plasma (total protein, albumin and globulin) showed maximum values in 30% CP fed group. It is concluded that proteolytic activity and ACP are the major digestive enzymes responsive to dietary CP in L. rohita fingerlings. Considering the cost effectiveness of the diet, and based on liver and plasma free amino acid levels and plasma protein fractions, 30% crude protein is recommended as the optimal dietary protein for L. rohita fingerlings.     

Cloning and expression of an outer membrane protein ompTS of Aeromonas hydrophila and study of immunogenicity in fish

The outer membrane proteins of the warm water fish pathogen, Aeromonas hydrophila have a role in the virulence of the organism and are potential candidates for vaccine development. In this study, the gene encoding an outer membrane protein designated ompTS was amplified by PCR excluding the region coding for signal peptide, cloned in pQE 30-UA Vector and expressed using induction with isopropyl thiogalactoside (IPTG). The size of the expressed protein was 37 kDa as estimated by migration in 10% sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Polyclonal antibodies were raised in mice and rabbit against the purified protein and the reaction of the antibody was confirmed by Western blotting using the purified protein and A. hydrophila cultures. The Indian major carp, Labeo rohita Hamilton was immunized using the purified protein and developed antibodies with mean titers of 1:4000 on day 14 and 1:12,000 on day 28 showing promise that the protein is highly immunogenic in fish.     

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.