Gilthead seabream (Sparus aurata L.) innate immune response after dietary administration of heat-inactivated potential probiotics

The effects of the dietary administration of two heat-inactivated whole bacteria from the Vibrionaceae family, singly or combined, on innate immune response of the seabream were studied. The two bacteria (Pdp11 and 51M6), which were obtained from the skin of gilthead seabream, showed in vitro characteristics that suggested they could be considered as potential fish probiotics. The fish were fed four different diets: control (non-supplemented), or diets supplemented with heat-inactivated bacteria at 10(8) cfu g(-1) Pdp11, 10(8) cfu g(-1) 51M6 or with 0.5 x 10(8) cfu g(-1) Pdp11 plus 0.5 x 10(8) cfu g(-1) 51M6 for 4 weeks. Six fish were sampled at weeks 1, 2, 3 and 4, when the main humoral (natural haemolytic complement activity and serum peroxidase content) and cellular innate immune responses (leucocyte peroxidase content, phagocytosis, respiratory burst and cytotoxicity) were evaluated. The serum peroxidase content and the natural haemolytic complement activity increased with time, reaching the highest values in the third and fourth weeks of feeding, respectively. The phagocytic ability of specimens fed the mixture of the two inactivated bacteria was significantly higher than in the controls after 2 and 3 weeks of treatment. The same activity increased significantly in seabream fed the Pdp11 diet for 2 weeks or the 51M6 diet for 3 weeks. Respiratory burst activity was unaffected by all the experimental diets at all times assayed. Cytotoxic activity had significantly increased after 3 weeks in fish fed the 51M6 diet. These results are discussed in terms of the usefulness of incorporating inactivated probiotic bacteria into fish diets.     

Nonspecific immune response of rainbow trout (Oncorhynchus mykiss Walbaum) in relation to different status of vitamin E and highly unsaturated fatty acids

This study was designed to examine the effects of dietary vitamin E (VE) on modulation of immune responses when supplied with two levels of n-3 highly unsaturated fatty acids (n-3 HUFA) in rainbow trout, Oncorhynchus mykiss. Six semipurified diets were prepared containing three levels of dietary VE (0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet) and n-3 HUFA either at 20 or 48% of dietary lipid provided from fish oil or docosahexaenoic acid (DHA) concentrated fish oil respectively. The diets were fed to rainbow trout (100 g initial mean weight) for 15 weeks. The VE, vitamin C (VC) content in plasma and tissues and the nonspecific immune responses, both humoral (alternative complement activity, total immunoglobulin) and cellular (phagocytosis, nonspecific cytotoxicity) were examined. VE contents in the kidney reflected the dietary input but were lower in fish fed 48% n-3 HUFA diets, and could have impaired some of immune responses compared to fish fed 20% n-3 HUFA. VC contents in kidney followed the same pattern as VE. Both humoral and cellular immune functions deteriorated in fish fed VE deficient diets whereas improvement in most of the parameters corresponded to its supplementation. However, the higher dose of dietary VE did not substantially enhance the responses assayed compared to the 100 mg dose. Besides clearly indicating the role of VE in maintaining the immune functions in fish in relation to dietary n-3 HUFA, this study has revealed that optimum health benefits could be achieved when VE is maintained slightly above the levels generally recommended for normal growth.     

Coriolus versicolor polysaccharides enhance the immune response of crucian carp (Corassius auratus gibelio) and protect against Aeromonas hydrophila

To investigate the effect of Coriolus versicolor polysaccharides (CVPS) on the immune response of crucian carp (Corassius auratus gibelio), fish were fed diets containing CVPS at different concentrations including 0.5, 1.0 and 2.0 g kg^?1 for 5 weeks. Other groups of fish were vaccinated by intraperitoneal injection (i.p.) against Aeromonas hydrophila with a killed bacterin at the beginning of the experiment and fed the same diets as described above. Additionally, control fish and vaccinated‐only fish were fed basal diets without CVPS supplementation. The phagocytosis, lysozyme activity, complement components C3 and C4, E‐C3bRR (Erythrocyte‐C3b rosette rate) and E‐CIRR (Erythrocyte‐immune complex rosette rate) levels and circulating antibody titers in the serum were monitored. Five weeks after feeding the prescribed diet, fish were challenged with A. hydrophila and the mortalities recorded. Results showed that feeding non‐vaccinated and vaccinated crucian carp with CVPS stimulated the phagocytosis of leukocytes, lysozyme, complement components C3 and C4, erythrocyte immune adherence, and circulatory antibody titers in serum in vaccinated crucian carp. Immune parameters increased to their highest levels after 3 weeks of feeding the diet containing 0.5 or 1.0 g kg^?1 CVPS. These doses also resulted in the highest protection in the challenge experiment. Best survival (85%) was in the vaccinated group fed the diet containing 1.0 g kg^?1 CVPS, whereas almost 80% of control fish (negative control) and 50% of vaccinated‐only fish (positive control) died.     

Inonotus obliquus containing diet enhances the innate immune mechanism and disease resistance in olive flounder Paralichythys olivaceus against Uronema marinum

The present study describes the effect of diet supplementation with Chaga mushroom, Inonotus obliquus extract at 0%, 0.01%, 0.1%, and 1.0% levels on the innate humoral (lysozyme, antiprotease, and complement), cellular responses (production of reactive oxygen and nitrogen species and myeloperoxidase), and disease resistance in olive flounder, Paralichythys olivaceus against Uronema marinum. The lysozyme activity and complement activity significantly increased in each diet on weeks 2 and 4 against pathogen. The serum antiprotease activity and reactive nitrogen intermediates production significantly increased in fish fed with 0.1% and 1.0% diets from weeks 1-4. However, reactive oxygen species production and myeloperoxidase activity significantly increased in 1.0% and 2.0% diets on weeks 2 and 4. In fish fed with 0.1% and 1.0% diets and challenged with U. marinum the cumulative mortality was 50% and 40% while in 0% and 0.01% diets the mortality was 85% and 55%. The results clearly indicate that supplementation diet with I. obliquus at 0.1% and 1.0% level positively enhance the immune system and confer disease resistance which may be potentially used as an immunoprophylactic in finfish culture.     

Effect of dietary ascorbic acid on growth and non-specific immune responses of tiger puffer, Takifugu rubripes

We report nutritional physiology and non-specific immune responses of ascorbic acid (AA) in puffer fish for the first time. This study aimed to examine the essentiality and requirements of AA in diets for the tiger puffer, Takifugu rubripes based on growth performance, liver AA and bone collagen concentration, and non-specific immune responses. Five casein-gelatin based semi-purified diets were formulated to contain five graded levels of l-ascorbyl-2-monophosphate at 0, 40, 80, 160 and 700mg/kg (designated as AMP0, AMP40, AMP80, AMP160 and AMP700, respectively) and fed to triplicate groups of fish. After 10weeks of feeding trial, growth performances of fish (initial body weight, 35g) fed the AMP0 were significantly lower compared to that of fish fed diets supplemented with AMP. The fish fed the AMP0 diet also exhibited significantly lower hematocrit, condition factor and hepatosomatic index compared to the fish fed diets supplemented with AMP. Phagocytic activity (NBT assay) was significantly lower in fish fed the AMP0 diet than in fish fed the AMP containing diets. Plasma lysozyme activity of fish fed the AMP80 and AMP160 was significantly higher than that of fish fed the AMP0. Dietary supplementation of AMP significantly increased the liver superoxide dismutase in the fish. Myeloperoxidase activity of fish fed the AMP0 was significantly lower compared to that of fish fed the AMP containing diets. Bone collagen level tended to increase numerically and total AA concentration in liver of fish was significantly increased in a dose dependent manner by the supplementation of AMP. Therefore, tiger puffer requires exogenous ascorbic acid and the optimum dietary level could be 29mg AA/kg diet for normal growth and physiology. Dietary AA concentration over 82mg/kg could be required to enhance non-specific immune responses of the fish. However, it does not seem that the fish needs an overdose of dietary AA (>160mg/kg) for better non-specific immune responses.     

Dietary administration of Lactobacillus delbrüeckii and Bacillus subtilis, single or combined, on gilthead seabream cellular innate immune responses

The effects of oral administration of Lactobacillus delbrüeckii ssp. lactis and Bacillus subtilis, single or combined, on gilthead seabream cellular innate immune responses were investigated. Fish were fed four different diets: control (non-supplemented); or diet supplemented with 10(7) cfu g(-1)L. delbrüeckii ssp. lactis; 10(7) cfu g(-1)B. subtilis; or with 0.5x10(7) cfu g(-1)L. delbrüeckii ssp. lactis and 0.5x10(7) cfu g(-1)B. subtilis. This feeding regime lasted for 3 weeks, and all experimental groups were then fed the control commercial diet for another week. Six fish were sampled at weeks 1, 2, 3 and 4. Head-kidney leucocytes were isolated and the main cellular innate immune parameters (leucocyte peroxidase content, phagocytosis, respiratory burst activity and cytotoxicity) were evaluated. Leucocyte peroxidase content was lower in all groups at week 3 but the levels tended to recover during the last week of the experiment. Respiratory burst activity was not affected at any time of the experiment in any of the experimental groups. However, phagocytic activity increased after 2 weeks of feeding the single bacteria-supplemented diets, whereas the combination of the two caused an increment which persisted for as long as the bacteria were being administered. Cytotoxic activity was also significantly increased after 3 weeks of feeding the mixture of the two bacteria. After 1 week back on the control diet, the parameters in the experimental groups had recovered or even dropped below those recorded in the control group, suggesting that the bacteria did not persist in the seabream gut.     

Dietary oligonucleotides from yeast RNA influence immune responses and resistance of hybrid striped bass (Morone chrysops x Morone saxatilis) to Streptococcus iniae infection

Three feeding trials were conducted to evaluate potential immunomodulatory effects of nucleotides in the diet of hybrid striped bass. A basal diet was formulated from menhaden fish meal to contain 40% crude protein and 10% lipid. An oligonucleotide product (Ascogen P) from brewer's yeast was added to the basal formulation at the manufacturer's recommended rate of 0.5% to produce the experimental diet. Each diet was fed to four replicate groups of juvenile hybrid striped bass for seven or eight weeks in two separate trials. After Trials 1 and 2, a Streptococcus iniae bath challenge was executed to test the effects of diet on disease resistance. No significant difference in growth performance was observed between fish fed the basal and experimental diets. Body composition of whole fish, hematocrit and serum lysozyme levels were observed to be within normal ranges and not influenced by dietary nucleotides. Neutrophil oxidative radical production of fish fed the nucleotide-supplemented diet was significantly (P=0.011) higher than in fish fed the basal diet. Significantly (P<0.05) enhanced survival after exposure to S. iniae also was generally observed in fish fed the nucleotide-supplemented diet. In addition, fish fed the nucleotide-supplemented diet tended to have a higher antibody response based on microtitration agglutination; however, the difference was not statistically significant because of high variation between individual fish. Long-term (16 weeks) administration of oligonucleotides in Trial 3 failed to show enhancement of immune responses between treatments. It is concluded that dietary oligonucleotides positively influenced immune responses and resistance of juvenile hybrid striped bass to S. iniae infection.     

Changes in some innate defence parameters of seabream (Sparus aurata L.) induced by retinol acetate

The effects of high doses of dietary or intraperitoneally (i.p.) injected retinol acetate on the gilthead seabream (Sparus aurata L.) innate immune system were studied. Gilthead seabream specimens were fed a commercial non-supplemented diet containing 1.75 mg of vitamin A kg(-1) (as control) or the same diet supplemented with 50, 150 or 300 mg of retinol acetate kg(-1) (as vitamin A source). After 1, 2, 4 or 6 weeks, serum samples and head-kidney leucocytes were obtained from each fish. Serum lysozyme activity and myeloperoxidase (MPO) content were unaffected by the vitamin A diet content. The phagocytic and respiratory burst activities of head-kidney leucocytes were established, as well as their myeloperoxidase content. While phagocytosis was not enhanced by dietary vitamin A intake and was even slightly decreased after 2 weeks, respiratory burst activity was enhanced in specimens fed supplements of 150 and 300 mg retinol acetate kg(-1) diet for 1 or 2 weeks. Leucocyte MPO content was also enhanced when seabream were fed the highest vitamin A dose for 2 or 4 weeks and after being fed the 150 or 50 mg supplemented diets for 4 or 6 weeks, respectively. Three different groups of seabream were i.p. injected with 1 ml of phosphate buffer containing an amount of retinol acetate equivalent to the daily dietary supplements from the first experiment (0-control-, 0.05 or 0.30 mg 100 g(-1) biomass). Both injection doses of retinol acetate were toxic for the gilthead seabream which showed hypervitaminic effects. These data show that retinol acetate plays an important role in the gilthead seabream nonspecific cellular immune system due to its antioxidant properties. They also point to the importance of the way in which it is administered, by dietary uptake or intraperitoneal injection.     

Effects of dietary beta-1, 3 glucan on innate immune response of large yellow croaker, Pseudosciaena crocea

The present study was conducted to investigate the effects of dietary beta-1, 3 glucan on the innate immune response and protection against Vibrio harveyi infection in large yellow croaker, Pseudosciaena crocea. A basal diet was supplemented with 0% (control), 0.09% (low) and 0.18% (high) beta-1, 3 glucan to formulate three experimental diets. Each diet was randomly allocated to triplicate groups of fish in floating sea cages (1.5 x 1.5 x 2.0m), and each cage was stocked with 100 fish (initial average weight 9.75+/-0.35 g). Fish were fed twice daily (05:00 and 17:00) to apparent satiation for 8 weeks. The results of 8 weeks feeding trial showed that low glucan supplementation (0.09%) significantly enhanced fish growth, whereas high supplementation (0.18%) did not. The serum lysozyme activity was significantly increased with the increase of dietary glucan (P < 0.05), and fish fed the diet with high glucan had significantly higher lysozyme activity compared with low glucan. There were no significant differences in alternative complement pathway (ACP) activity between fish fed diets with and without supplementation of glucan. The phagocytosis percentage (PP) and respiratory burst activity in fish fed the diet with 0.09% glucan were significantly higher than those in fish fed with the control diet (P < 0.05), but both immunological parameters significantly decreased in fish fed the diet with high supplementation compared with low supplementation and no significant difference was observed between the control and high supplementation groups. The challenge experiment showed that fish fed the diet with low glucan had significantly lower cumulative mortality compared with the control and high glucan groups (P < 0.05), but no significant difference was observed between the control and high supplementation groups. These results suggested that low glucan could enhance growth and innate immunity of large yellow croaker with an 8-week oral administration, but higher supplementation did not influence growth, or further improve immunity of large yellow croaker.     

Influence of diet enriched with green tea on innate humoral and cellular immune response of kelp grouper (Epinephelus bruneus) to Vibrio carchariae infection

Effect of diet enriched with green tea at 0, 0.01, 0.1 or 1.0% levels on immune responses such as non-specific humoral (lysozyme, antiprotease and complement) and cellular (myeloperoxidase content, production of reactive oxygen, and nitrogen species) and disease resistance on week 1, 2 or 4 in kelp grouper Epinephelus bruneus challenged with Vibrio carchariae (2.47 × 10(8) CFU ml(-1)) was quantified. At all doses green tea supplementation significantly enhanced the serum lysozyme activity from weeks 1 to 4. On the other hand, after week 2 the serum hemolytic complement activity, leucocyte myeloperoxidase content and reactive nitrogen species protection significantly increased in groups fed with 0.01 and 0.1% green tea supplementation diets. The serum antiprotease activity significantly increased in group fed with at 1.0% green tea from week 1 to 4. However, all diets except at 0.01% level resulted in a significant decrease in reactive oxygen species protection during the experimental period. Challenged groups fed with green tea enriched diet at 0.01 and 0.1% level had a higher relative percent survival than with 1.0% diet on week 1, 2 or 4. The results suggest that dietary administration of green tea supplementation at a concentration of 0.01 and 0.1% level positively enhances the non-specific humoral and cellular immune responses and disease resistance of kelp grouper E. bruneus to V. carchariae.     

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.     

Effect of dietary vitamin C on the growth performance and innate immunity of juvenile cobia (Rachycentron canadum)

This study was conducted to evaluate the effects of dietary vitamin C on growth performance, hematologic parameters and innate immune responses in juvenile cobia, Rachycentron canadum. Seven practical diets were formulated to contain 0.0 (as the basal diet), 13.6, 27.2, 54.4, 96.6, 193.4 and 386.5 mg ascorbic acid equivalent kg(-1) diet. Each diet was fed to triplicate groups of juvenile cobia with initial body weight of 5.5 g in 500-L cylindrical fiberglass tank. The results of 8 weeks feeding trial showed that typical vitamin C-deficient signs such as spinal deformation and body nigrescence were observed in the fish fed the basal diet. Fish fed the basal diet had significantly lower weight gain, specific growth rate (SGR), protein efficiency ratio (PER) and feed efficiency (FE) than those fed the diets supplemented with vitamin C, but no significant differences were observed among diets supplemented with vitamin C. However, survival rate was significantly affected by the dietary vitamin C levels, fish fed the basal diet had lower survival rate than those fed the diets supplemented with vitamin C. The ascorbic acid concentration in liver was correlated positively with the dietary vitamin C levels, however, the thiobarbituric acid reactive substances (TBARS) concentrations in liver was not significantly affected by the dietary vitamin C levels, although, fish fed the basal diet had the highest TBARS values among all treatments. The activities of serum lysozyme, superoxide dismutase (SOD), alkaline phophatase (AKP) and total immunoglobulin (Ig) were significantly influenced by the dietary vitamin C levels, fish fed the basal diet had lower lysozyme, SOD, AKP and total Ig than those fed diets supplemented with vitamin C. The serum glucose and triglyceride concentrations were significantly affected by the dietary vitamin C levels. Fish fed the basal diet had lower red blood cell and hemoglobin values than those fed the vitamin C supplemented diets. The challenge experiment with Vibrio harveyi showed that lower cumulative survival was in fish fed the unsupplemented diet, the cumulative survival were significantly increased with increase of the dietary ascorbic acid levels from 13.6 to 96.6 mg kg(-1), while the cumulative survival reached plateau when dietary ascorbic acid levels increased from 96.6 to 386.5 mg kg(-1). These results indicated that dietary vitamin C did significantly influence on growth performance and immune response of juvenile cobia.     

Dietary supplementation with chitin and chitosan on haematology and innate immune response in Epinephelus bruneus against Philasterides dicentrarchi

The present study investigated the effect of 1.0% chitin and chitosan supplementation diets on haematology and immune response in Kelp grouper, Epinephelus bruneus against protozoan parasite, Philasterides dicentrarchi. The red blood cells (RBC), white blood cells (WBC), haemoglobin levels, lymphocytes, monocytes, and neutrophils significantly increased in kelp grouper fed with chitin or chitosan enriched diets against P. dicentrarchi. The mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), and thrombocytes did not significantly change against pathogen. The phagocytic activity, respiratory burst activity, complement activity, antiprotease activity, and α2-macroglobulin were significantly enhanced in fish fed with 1% chitin and chitosan diet on weeks 2 and 4. The lysozyme activity, total protein, and myeloperoxidase activity significantly increased in fish fed with chitin or chitosan supplementation diet from weeks 1 to 4 against pathogen. The cumulative mortality was found low in fish fed with chitin and chitosan enriched diets than those of control against pathogen. The present study suggests that supplementation of 1.0% chitin or chitosan in diets positively enhances immune response and affords disease resistance in kelp grouper, E. bruneus against P. dicentrarchi infection.     

Effect of dietary supplementation with Suaeda maritima on blood physiology, innate immune response, and disease resistance in olive flounder against Miamiensis avidus

The effect of Suaeda maritima enriched diet on blood physiology, innate immune response, and disease resistance in olive flounder Paralichythys olivaceus against Miamiensis avidus on weeks 1, 2, and 4 was investigated. Feeding with any enriched diet and then challenging with M. avidus significantly increased white blood cells (WBC) on weeks 2 and 4; the red blood cells (RBC) significantly increased with 0.1% and 1.0% enriched diets on week 4. The hemoglobin (Hb) and hematocrit (Ht) levels significantly increased when fed with 0.1% and 1.0% supplementation diets on weeks 2 and 4. The mean corpuscular volume (MCV) did not significantly vary with any diet and time; however the mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) significantly increased with 0.1% and 1.0% supplementation diets on weeks 2 and 4. The leukocytes such as lymphocytes (Lym), monocytes (Mon), neutrophils (Neu) and biochemical parameters such as total protein (TP), glucose (GLU), and calcium (CAL) levels significantly increased in 0.1% and 1.0% supplementation diet fed groups on weeks 2 and 4. The serum lysozyme activity was significantly enhanced in 0.1% and 1.0% supplementation diet fed groups from weeks 1 to 4 when compared to the control (0% herbal extract enriched diet). The scuticocidal activity and respiratory burst activity were significantly enhanced when fish were fed with 0.1% and 1.0% supplementation diets from weeks 2 and 4. The protective effect in terms of cumulative mortality (50% and 40%) was low in groups on being fed with 0.1% and 1.0% supplemented diet. Therefore the present study suggested that 0.1% and 1.0% S. maritime-supplemented diets protect the hematological and biochemical parameters, improving the innate immunity, affording protection disease from M. avidus infection in olive flounder.     

The effect of dietary phosphorus deficiency on the immune responses of European whitefish (Coregonus lavaretus L.)

Low phosphorous (P) feeds in aquaculture are recommended to reduce eutrophication of water systems. However, the feed should be adequate for normal growth and intact immune defence. Influence of low dietary P supply on non-specific and specific immune defence of European whitefish (Coregonus lavaretus) was studied in two trials. For Trial 1, a semi-purified, low-P diet was formulated and supplied with 0, 2.5, 5.0, 7.5, or 10.0 g P kg(-1)to obtain a P gradient of 4.4-14.9 g kg(-1)diet. Diets were fed to four replicate groups of fingerling whitefish for 42 days in a flow-through, freshwater system maintained at 15 degrees C. Fish fed with the P-unsupplemented diet had significantly lower plasma immunoglobulin M (IgM) levels than fish fed with the P-fortified diets (means 2.53 vs. 3.19 mg ml(-1); P=0.047). Plasma lysozyme activity did not differ between fish fed with the P-unsupplemented diet and fish fed with the P-fortified diets (means 21.8 vs. 25.5 U ml(-1); P=0.107). For Trial 2, fish were acclimated for 49 days by feeding the lowest or highest dietary P contents, and thereafter immunised with a single intraperitoneal injection of a novel antigen, bovine gamma globulin (BGG). A clear antibody response against BGG was elicited but the antibody levels did not differ between fish fed low-P or high-P contents. Similar to Trial 1, plasma IgM was lower in fish fed low-P diets, and low-P diet did not influence plasma lysozyme activity. In both trials the growth of fish, having received low-P diet, was significantly lowered. It is concluded that P deficiency has only minor effects on the immune parameters in whitefish, and the practical aquafeed with P contents sufficient for normal growth does not compromise immune functions of this species.     

Immunostimulant effects of Cotinus coggyria on rainbow trout (Oncorhynchus mykiss)

In this study, non-specific immune effects of tetra (Cotinus coggyria) on rainbow trout (Oncorhynchus mykiss) by dietary intake were investigated. Fish were fed daily ad libitum with diets containing 0.5% and 1.0% tetra for 3 weeks. After this period, fish were switched back to the basal diet for additional 6 weeks. Extracellular and intracellular respiratory burst activities, phagocytosis in blood leukocytes, lysozyme activities, and total plasma protein levels were evaluated at the end of the tetra feeding period and every 3 weeks during the basal diet period. Extracellular and intracellular respiratory burst activities, phagocytic activity, lysozyme activity and total protein level parameters of the groups containing 0.5% and 1.0% tetra were higher than the control group at the end of the 3rd, 6th and 9th weeks, respectively (P < 0.05). The highest values of the non-specific immune parameters were observed in the group fed with 1.0% tetra. Tetra groups did not show any significant difference (P > 0.05) in terms of specific growth rate and average weight of the fish.     

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.     

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.     

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 effect of vitamin B6 deficiency on cytotoxic immune responses of T cells, antibodies, and natural killer cells, and phagocytosis by macrophages

The effect of vitamin B6 on cytotoxic immune responses of T cells, natural killer (NK) cells, cytotoxic antibody production, and macrophage phagocytosis was assessed in 5-week-old female C57B1/6 mice. Mice were fed 20% casein diets with pyridoxine (PN) added at 7, 1, 0.1, or 0 mg/kg diet, which represents 700, 100, 10, and 0% of requirement, respectively. Compared to mice fed 7 or 1 mg PN diet, animals fed 0 or 0.1 mg PN diet showed significantly reduced primary splenic and peritoneal T-cell-mediated cytotoxicity (CMC). Animals fed 0 mg PN diet also showed significantly depressed secondary T CMC of splenic and peritoneal lymphocytes against P815 tumor cells. Complement-dependent antibody-mediated cytotoxicity against P815 cells, phagocytosis of SRBC by macrophages, and native and interferon-induced NK cell activities against YAC cells were not affected by the level of vitamin B6 intake. The percentage of macrophages present in the peritoneal exudate cells was increased in animals fed the 0 mg PN diet. The immune responses were not enhanced or altered by the excess intake of vitamin B6 (7 mg PN). It appears that vitamin B6 is an essential nutrient for maintenance of normal T-cell function in vivo.