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1.
The comparative effects of Freund's and Aloe vera gel as adjuvants on the expression of IL‐1β and TNF‐α genes were studied in vaccinated common carp (Cyprinus carpio) with Aeromonas hydrophila bacterin. Fishes were intraperitoneally immunized with A. hydrophila bacterin in combination with Aloe vera gel or Freund's and also without any adjuvant. At day 28 after immunization, all groups were challenged by lethal dose of A. hydrophila (107 cells/fish). Changes in the expression of IL‐1β and TNF‐α genes were evaluated in anterior kidney before challenge and 12, 24, 72 and 7 days postchallenge using quantitative real‐time PCR. Higher expression levels of both genes were observed in all vaccinated groups compared with non‐immunized group. Fishes which received Aloe vera gel showed higher expression of IL‐1β and TNF‐α in relation to animals which vaccinated with or without Freund's adjuvant. We concluded that Aloe vera gel in compared with Freund's adjuvant had a more stimulatory effect on the expression of immune‐related genes in vaccinated common carp and it can use as a novel adjuvant in aquaculture.  相似文献   

2.
A 35 days feeding trial was conducted to assess the haemato‐immunological response of Labeo rohita fingerlings fed ethanolic leaf extracts of Psidium guajava and Mangifera indica, and infected with Aeromonas hydrophila. Six iso‐nitrogenous (354.6–361.6 g kg?1) purified diets were prepared with graded level of leaf extracts viz., control (basal feed without any extract); TG‐5 (5 g kg?1 guava extract); TG‐10 (10 g kg?1 guava extract); TM‐5 (5 g kg?1 mango extract); TM‐10 (10 g kg?1 mango extract); and TGM (5 g kg?1 guava extract +5 g kg?1 mango extract). Haematological, immunological, biochemical, along with antioxidant enzyme activities were examined after a 35 day‐feeding trial and following a 7 day challenge with A. hydrophila. The haemoglobin, total leucocyte and erythrocyte counts, respiratory burst activity, lysozyme, total protein, albumin and globulin contents increased significantly (P < 0.05) in leaf extracts fed groups compared with the control in pre‐ and post‐challenge conditions. A significant (P < 0.05) decrease was observed in SOD (superoxide dismutase) and catalase activities of the treatment groups compared with the higher value in control. The trends in mortality indicated that groups of fish showing significantly elevated haemato‐immunological responses had the lowest mortality following challenge with A. hydrophila. The results showed that extracts of P. guajava and M. indica appear to be potential immunostimulant at an inclusion level of 5 g kg?1 in the diet of rohu. But, mixing of both the extract at similar level did not show any synergistic effect, which needs to be tested at its lower level of inclusion.  相似文献   

3.
Diseases caused by motile aeromonads in freshwater fish have been generally assumed to be linked with mainly Aeromonas hydrophila while other species were probably overlooked. Here, we identified two isolates of non‐A. hydrophila recovered from Nile tilapia exhibiting disease and mortality after exposed to transport‐induced stress and subsequently confirmed their virulence in artificial infection. The bacterial isolates were identified as Aeromonas jandaei and Aeromonas veronii based on phenotypic features and homology of 16S rDNA. Experimental infection revealed that the high dose of A. jandaei (3.7 × 106 CFU fish?1) and A. veronii (8.9 × 106 CFU fish?1) killed 100% of experimental fish within 24 h, while a 10‐fold reduction dose killed 70% and 50% of fish, respectively. When the challenge dose was reduced 100‐fold, mortality of the fish exposed to A. jandaei and A. veronii decreased to 20% and 10%, respectively. The survivors from the latter dose administration were rechallenged with respective bacterial species. Lower mortality of rechallenged fish (0%–12.5%) compared to the control groups receiving a primary infection (37.5%) suggested that the survivors after primary infection were able to resist secondary infection. Fish exposed to either A. jandaei or A. veronii exhibited similar clinical signs and histological manifestation.  相似文献   

4.
In this study, the effect of extracts of two herbs (Oliviera decumbens and Satureja khuzestanica) on immune response of carp was investigated. At the beginning of experiment, fish were divided to two groups including vaccinated (using vaccine developed against A. hydrophila) and non‐vaccinated. Fish in both groups were fed diets containing O. decumbens and S. khuzestanica and combination of two herbal extracts for 5 weeks. Control fish (negative control) and fish vaccinated only (positive control) were fed basal diets without supplements of herbal extracts. Lysozyme activity, antibody titre, complement activity and bactericidal activity in serum were measured. After 5 weeks feeding, fish were infected with A. hydrophila and mortalities were recorded. In both experimental groups, no significant differences were found in terms of alternative haemolytic complement (ACH50) activity and antibody titres of Serum. In non‐vaccinated fish group, lysozyme and bactericidal activity of fish fed S. khuzestanica or combination of O. decumbens and S. khuzestanica was higher compared with control and other experimental treatments. In vaccinated fish group, the lysozyme and bactericidal activity was not significant in all treatments compared with control group. The results of this study showed that feeding non‐vaccinated and vaccinated carp with only S. khuzestanica or in combination with O. decumbens enhance only some immunity indices including lysozyme and bactericidal activity in non‐vaccinated fish and these extracts have no immunological stimulatory role on vaccinated individuals.  相似文献   

5.
This study was conducted to determine the systemic, mucosal immunity and protective capacity of the feed‐based adjuvant vaccine (FAV) of Streptococcus agalactiae following oral vaccination against streptococcosis in tilapias. Two hundred and sixteen red tilapia fish were divided into three major groups. Each major group consisted eight tilapia kept in nine 2000 L glass aquaria. At day 0, all fish from the FAV group were fed with feed that had been incorporated with an adjuvant, while fish in the feed‐based vaccine (FNV) group were fed with vaccine incorporated into the pellet without adjuvant. Fish in the control‐unvaccinated group, FC, were fed with normal commercial pellet. Booster dose was performed on day 14 post immunization. Fish from each group were sacrificed on a weekly basis for the entire 7 weeks. Serum, body mucus and gut lavage fluid were evaluated for antibody responses by indirect ELISA, while histological examination was carried out on the gut following intraperitoneal challenge. The FAV group had a significantly higher protection (P < 0.05) following challenge with 3.4 × 109 CFU mL?1 of live S. agalactiae than FNV group. This level of protection may be due to high antibody responses, increase in size of gut‐associated lymphoid tissue and high number of lymphocytes in the FAV group.  相似文献   

6.
This study evaluated the effects of basil (Ocimum basilicum) leaves extract supplement on growth, blood parameters and resistance to Aeromonas hydrophila in Cyprinus carpio fingerlings. Basil leaves were mixed thoroughly with feed at 0, 100, 200, 400, 800 and 1600 mg kg?1 of diet and were fed in triplicate group for 2 months. At the end of this period, growth performance and survival were determined. Then fish were challenged intraperitoneally with A. hydrophila and mortalities were recorded up to 10 days post challenge. Results indicated that WBC, RBC, Ht, Hb, total protein, albumin and globulin were higher (P < 0.05) in fish fed diets containing O. basilicum compared with the control. Highest specific growth rate values were observed in 400 mg kg?1 group. Feed conversion ratio was significantly lower (P < 0.05) in fingerlings fed 400 and 800 mg O. basilicum kg?1 dry diet. After 10 days post challenge, total protein, WBC, RBC and Hb were significantly higher in 400 mg kg?1 compared with other groups. These results reveal that a dietary O. basilicum leaves extract of 400 mg kg?1 fed for 60 days leads to increased growth performance and survival rate as well as improved feeding efficiency in common carp fingerlings rendering them more resistant against infection by A. hydrophila.  相似文献   

7.
An 11‐week feeding trial was conducted to evaluate the effect of dietary methionine on the growth, antioxidant status, innate immune response and disease resistance to Aeromonas hydrophila of juvenile yellow catfish. Six isonitrogenous and isolipidic practical diets were formulated to contain different graded methionine levels ranging from 6.1 to 16.4 g kg?1 of dry weight. The results indicated that growth performance and feed utilization were significantly influenced by the dietary methionine levels; fish fed the diet containing 6.1 g kg?1 methionine level had lower specific growth rate, percentage weight gain (PWG), feed efficiency and protein efficiency ratio than those fed the other diets (P < 0.05). Fish fed the diet containing 16.4 g kg?1 methionine level had lowest protein contents in whole body and muscle among all treatments. Triacylglycerols, cholesterol, aspartate aminotransferase, alanine aminotransferase and haemoglobin (Hb) in plasma or whole blood were significantly affected by dietary methionine levels. Fish fed the diet containing 6.1 g kg?1 methionine level had higher superoxide dismutase, glutathione peroxidase activities and malondialdehyde values than those fed other diets. Fish fed diets containing 9.7 and 11.8 g kg?1 methionine levels had higher lysozyme activity, total immune globulin, phagocytic activity and respiratory burst than those fed other diets. The lowest survival after A. hydrophila challenge was observed in fish fed a diet containing 6.1 g kg?1 methionine. Quadratic regression analysis of PWG against dietary methionine levels indicated that the optimal dietary methionine requirement for the maximum growth of juvenile yellow catfish was estimated to be 11.5 g kg?1 of the diet in the presence of 4.0 g kg?1 cystine (corresponding to 23.5 g kg?1 of dietary protein on a dry weight basis).  相似文献   

8.
The role of dietary linolenic acid (LN), vitamin E (E) and vitamin C (C) in regulating fish growth and immune response was tested on juvenile darkbarbel catfish Pelteobagrus vachelli. Five dietary combinations were used (?E?LN, +E?LN, ?E+LN, +E+LN and ?C+E+LN; ‘+’ with addition and ‘?’ without addition) in triplicate. Weight gain was highest in the ?E+LN feeding group. Red blood cell in fish fed the +E+LN diet was highest. The haematocrit and haemoglobin of fish fed the ?E+LN diet was lowest. Superoxide dismutase, catalase, glutathione peroxidase and glucose‐6‐phosphate dehydrogenase activities in fish fed the ?E+LN diet were higher than those in fish fed other diets. Malondialdehyde in fish fed the ?C+E+LN diet was highest. Fish fed the +E+LN diet had higher levels of lysozyme activity, serum protein, complements C3 and C4, and immunoglobulin contents than fish fed other diets. Fish fed the +E+LN diet showed lower mortality and higher antibody titre than fish fed other diets after the fish were challenged with Aeromonas hydrophila for 14 day. This study suggests that the growth of darkbabel catfish is improved by increasing dietary linolenic acids. The diets with high linolenic acid, vitamin E and vitamin C can enhance the immune response and resistance in darkbarbel catfish challenged with A. hydrophila.  相似文献   

9.
This study evaluated the effects of dietary supplementation with two symbiotics in the hybrid surubim (Pseudoplatystoma corruscans × P. reticulatum) prior to and after challenge with Aeromonas hydrophila. The fish were divided into unsupplemented fish, supplemented fish with Weissella cibaria and inulin, and supplemented fish with Lactobacillus plantarum and inulin. Twenty days after being fed symbiotics, the fish were sampled for immunological, haematological, and microbiological analysis pre‐challenge. After this period, they were challenged with Aeromonas hydrophila, and after 96 h the fish were sampled for blood collection and survival. Fish fed W. cibaria and inulin from the pre‐challenge showed the highest values of lysozyme activity. Fish fed L. plantarum and inulin presented a higher number of thrombocytes and granular leukocyte PAS+ than the other fish. After challenge, fish fed both symbiotics presented an increased red blood cells number. Fish fed L. plantarum and inulin showed an increased total leucocyte count (WBC), neutrophils, and monocytes number as well as total immunoglobulin. The W. cibaria‐ and inulin‐supplemented fish showed improved haematological and immunological parameters and reduced cumulative mortality after the challenge.  相似文献   

10.
Four alkaloids (Sanguinarine, 6‐Methoxyl‐dihydro‐chelerythrine, Cryptopine and β‐Allocryptopine) were isolated from aerial parts of Macleaya microcarpa (Maxim) Fedde using bioassay‐guided isolation method, and the inhibitory activity of ethanolic extract, various fractions and these four alkaloids against four fish pathogenic bacteria (Aeromonas hydrophila, Aeromonas salmonicida, Vibrio anguillarum and Vibrio harveyi) was assessed in vitro using the agar dilution method and the microdilution assay method respectively. A. hydrophila was the most sensitive strain to all the tested compounds. Minimum inhibitory concentration (MIC) values were lower for sanguinarine against all tested Gram‐negative strains than other three alkaloids, with MIC values of 12.5 mg L?1 for A. hydrophila and 50 mg L?1 to other pathogenic bacteria. Followed by 6‐methoxyl‐dihydro‐chelerythrine, which showed considerable antibacterial activity with MIC values of 80 mg L?1 for A. hydrophila, 100 mg L?1 for V. harveyi, and 125 mg L?1 for both V. anguillarum and A. salmonicida. Cryptopine and β‐allocryptopine revealed similar inhibitory activity with MIC values of 100 mg L?1 for A. hydrophila and 200 mg L?1 for other three bacterial species. These finding provided evidence that extract, as well as isolated compounds from M. microcarpa might be potential sources novel antibacterial agents for the treatment of fish infectious diseases.  相似文献   

11.
An experimental trial was conducted for 90 days to evaluate the growth performance, immunophysiological response of GIFT strain of Tilapia in biofloc‐based rearing system and to assess the relative percentage survival in 3 days after challenging with the virulent strain of Aeromonas hydrophila. Fingerlings with an average body weight 0.98 ± 0.06 g were stocked in triplicate at different stocking densities of 200 (SD1), 250 (SD2), 300 (SD3) and 350 (SD4) m?3 in biofloc‐based treatments and 150 (C) m?3 in control (clear water). Biofloc‐based units (SD1 and SD2) obtained significantly better (P < 0.05) growth performances at the end of the experimental period. Mean body weight of fish in biofloc‐based units showed a decreasing trend with increase in stocking density with 100% survival in all units including control. The stress parameters were significantly lower in biofloc‐based rearing units especially in treatments SD1 and SD2 as compared to the control. The fish from the biofloc‐based units (SD1 and SD2) possessed significantly (P < 0.05) higher immune status as compared to control and other biofloc treatments in terms of respiratory burst, serum lysozyme and myeloperoxidase activity. Relative survival percentages were significantly better in biofloc treatments with highest in SD1 and SD2 (83.33%) after challenge study. GIFT strain of Tilapia at higher stocking densities 200–250 nos m?3 can be taken as optimum stocking density whereas higher stocking densities up to 350 nos m?3 can be reared in the biofloc systems without compromising the growth and immunity.  相似文献   

12.
The specific and non‐specific immune parameters and protection of European eels (Anguilla anguilla) were evaluated after bathing eels with Aeromonas hydrophila. Two hundred eels were distributed into two equal groups and bathed with Phosphate‐buffered saline (Control group) or 1.0 × 107 cfu mL?1 A. hydrophila (Test group) for 1 h respectively. Then, eels were bled aseptically from the caudal sinus on 1, 4, 7, 14 and 28 days post treatment. The blood cells were used to evaluate the cellular immunity and the serum was used to determine the titres of specific antibody as well as the activities of superoxide dismutase (SOD) and lysozyme. Eels from both groups were challenged by intraperitoneal injection of 1.0 × 107 cfu of A. hydrophila on 28 and 42 days post bathing. The results show that eels bathed in A. hydrophila significantly (P < 0.05) enhanced the proliferation of different types of blood cells and the serum titres of anti‐A. hydrophila antibody. The Relative Percent Survival (RPS) after challenge on 28 and 42 days post bathing in Test group vs. Control group was 40% and 50% respectively. These results suggest that bathing European eels in A. hydrophila would positively affect specific as well as non‐specific immune parameters and protect against A. hydrophila infection in freshwater farming.  相似文献   

13.
In the present study, the effects of Artemia supplemented with 2‐β‐mercapto‐ethanol (β‐ME) treated yeast cell, Saccharomyces cerevisiae, on growth and reproductive performance, lysozyme activity, and disease resistance to Aeromonas hydrophila of freshwater ornamental species, Poecilia latipinna, were investigated. Within 60 days, molly fish were fed with three treatments including commercial food (T1), un‐supplemented Artemia (T2), and Artemia supplemented with β‐ME‐treated yeast cell (at concentration of 4 × 107 CFU/L of water) (T3). After the feeding period, the fish were exposed to 100 μl of a suspension (1.1 × 107 cells/ml) of A. hydrophila (BCCM5/LMG3279) and the cumulative mortality rates were recorded for 12 days. No significant difference was found between survival rate and growth performance of P. latipinna except for weight gain that was higher in fish fed through Artemia supplemented with β‐ME‐treated yeast cell compared to control group. Fecundity rate was significantly improved in fish fed using T3 with the maximum amount of 49.5 ± 2.29 per female (p < 0.05). Besides, lysozyme activity was significantly increased in group 3 (p < 0.05). Moreover, lowest fish mortality was significantly observed in this treatment (p < 0.05). In addition, the number of colonies formed by yeast cell in T3 (634 × 103 CFU/g intestine) showed significant difference with other treatments (p < 0.05). In sum, Artemia enriched with β‐ME‐treated yeast improved reproductive indices, immune responses, and resistance against A. hydrophila of P. latipinna.  相似文献   

14.
An 11‐week growth trial was conducted to determine dietary myo‐inositol (MI) requirement for juvenile gibel carp (Carassius auratus gibelio). Myo‐inositol was supplemented to the basal diet to formulate six purified diets containing 1, 56, 107, 146, 194 and 247 mg MI kg?1 diet, respectively. Each diet was fed to triplicate groups of juvenile gibel carp (initial body weight 3.38 ± 0.27 g, mean ± SD) in a flow‐through system. The diets were randomly assigned to different fish tanks. Fish fed ≥ 107 mg MI kg?1 diet had significantly higher weight gain (WG), feed efficiency (FE) and protein efficiency ratio than those fed 1 mg MI kg?1 diet. Fish fed ≥ 56 mg MI kg?1 diet had higher feeding rate and survival compared with fish fed 1 mg MI kg?1 diet. Dietary supplemental inositol did not affect fish liver inositol concentration. Fish fed ≥ 56 mg MI kg?1 diet had higher body dry matter, crude protein and gross energy and lower hepatosomatic index than fish fed 1 mg MI kg?1 diet. Dietary inositol supplementation decreased fish body ash. Quadratic regression of weight gain indicated that the myo‐inositol requirement to maximum growth for juvenile gibel carp was 165.3 mg MI kg?1 diet.  相似文献   

15.
We investigated the efficacy of praziquantel (PZQ) and fenbendazole (FBZ), each administered by bath and orally, against the monogenean Lepidotrema bidyana Murray, a gill parasite of the freshwater fish silver perch, Bidyanus bidyanus (Mitchell). PZQ and FBZ were each administered by bath at 10 mg L?1 for 48 h and on surface‐coated feed pellets at 75 mg kg?1 per body weight (BW) per day for 6 days. Bath treatments of PZQ and FBZ had an efficacy of 99% and 91%, respectively, against adult L. bidyana. Oral treatments of PZQ and FBZ had an efficacy of 79% and 95%, respectively, against adult L. bidyana. Fish rejected feed pellets surface‐coated with PZQ, suggesting that palatability of surface‐coated PZQ‐medicated feed is poor, which undermined efficacy. In all trials, some juvenile parasites were present on fish after treatment during efficacy assessment, indicating that efficacy may be lower against juvenile parasites or that recruitment occurred post‐treatment, demonstrating that repeat treatments are necessary to effectively control L. bidyana in aquaculture.  相似文献   

16.
Fish are always susceptible to a wide variety of deadly pathogens which cause a huge loss in aquaculture industries. In this investigation, we have demonstrated the in vivo probiotic efficiency of Bacillus sp. MVF1 (GenBank Acc. No. KP256503) in Labeo rohita challenged with pathogenic strain of Aeromonas hydrophila (MTCC 1739). To check the probiotic potential of the selected bacterial strain, fish were divided into four groups: control, D1, D2 and D3. A total of 100 days (70 days probiotic feeding + 71th day sampling and 28 days challenged test + 29th day sampling) of feeding trial was conducted. To establish the probiotic potential of Bacillus sp. MVF1, certain haematological parameters (haemoglobin, total erythrocyte and leucocyte count), serum biochemical parameters (total protein, albumin and globulin), immune parameters (serum lysozyme and total IgM levels) and hepatic stress profile (malondialdehyde production, superoxide dismutase and catalase activity) have been measured. Our results demonstrated that red blood cell number, white blood cell number and haemoglobin content were much higher in D2 group fish compared to other groups and control fish. Similarly, total protein contents, albumin concentration, globulin concentration, lysozyme activity and IgM production were also recorded to be highest in D2 group fish. This finding clearly indicated the probiotic potential of Bacillus sp. MVF1 in L. rohita. Furthermore, our results also demonstrated that 1 × 107 CFU g?1 feed (D2) provides better immunity compared to 1 × 105 (D1) and 1 × 109 (D3). Due to beneficial effects, the bacterium Bacillus sp. MVF1 might be useful in aquaculture industries to reduce the disease susceptibility.  相似文献   

17.
Intensive culture of the hybrid surubim (Pseudoplatystoma corruscans × Pseudoplatystoma fasciatum) in Brazil is responsible for the occurrence of diseases and consequent economic losses. However, the causative agents are not well known. The objective of this study was to isolate and to characterize the pathogenic agent responsible for mortalities in cultured surubim and to demonstrate its virulence. Ten fish from a fish farm located in the Mato Grosso do Sul State (Brazil) were collected and 14 haemolytic bacteria characterized as Aeromonas hydrophila were isolated from the kidneys (eight) and brain (six). As an experimental challenge, fish weighing 98.1±23.6 g were injected with 1 mL of saline solution and 2 × 102, 2 × 104, 2 × 106 and 2 × 108 CFU A. hydrophila mL?1. Fish infected with 2 × 108 CFU showed increased external and internal symptoms and mortality of 50±12.5% after 96 h. Increased A. hydrophila concentration was responsible for a decrease in haematocrit percentage and erythrocyte number, lymphocytes and eosinophils, as well as an increase in monocytes, neutrophils, serum agglutination titre and serum antimicrobial activity. It was concluded that A. hydrophila was responsible for characteristic symptoms of bacterial haemorrhagic septicaemia as well as important haematological and immunological alterations, which led to surubim mortality.  相似文献   

18.
The efficacy of copper sulphate (CuSO4) against the early stages of an experimental acute infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus) was evaluated. Fish were challenged, by waterborne exposure to F. columnare in an ultra‐low flow‐through water delivery system, and treated with CuSO4 at 4.2 and 2.1 mg L?1 at 5.5 h post challenge for 4 h. Bacterial challenged non‐treated fish acted as a positive control and non‐challenged non‐treated fish acted as a negative control. Fish challenged with F. columnare and treated with CuSO4 at 4.2 and 2.1 mg L?1 post challenge had mortalities of 6.4% and 18.3%, respectively, compared with the positive control, which had 90.2% mortality. The mortality of challenged fish treated with CuSO4 at 4.2 and 2.1 mg L?1 was significantly different from the positive control. There was no significant difference between the mortalities of the 4.2 and 2.1 mg L?1 treatments. The results suggest that CuSO4 has clear therapeutic value against columnaris infections.  相似文献   

19.
Growth, survival and production of endangered Indian butter catfish (Ompok bimaculatus) fingerlings were examined at different stocking densities. The experiment was conducted for 8 months in nine earthen ponds having an area of 0.03 ha each. 30‐day‐old fingerling, stocked at 40 000 ha?1 was designated as treatment‐1 (T1), 50 000 ha?1 as treatment‐2 (T2) and 60 000 ha?1 as treatment‐3 (T3). At stocking, all fingerlings were of same age group with a mean length and weight of 3.36 ± 0.08 cm and weight of 0.83 ± 0.02 g respectively. Fish in all the treatments were fed with a mixture of rice bran (50%), mustard oil cake (30%), fish meal (19%) and vitamin‐mineral premix (1%). Physicochemical parameters, plankton populations and soil parameters were at the optimum level for fish culture. Highest weight gain was observed in T1 and lowest in T3. Final length, weight and survival of fish also followed the same trend as weight gain. Highest specific growth rate was observed in T1 followed by T2 and T3. Feed conversion ratio was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher amount of fish was produced in T1 than T2 and T3 respectively. Higher net benefit was obtained from T1 than from T2 and T3. Overall, the highest growth, survival and benefit of fish were obtained at a density of 40 000 fingerlings ha?1. Hence, of the three stocking densities, 40 000 fingerlings ha?1 appears to be the most suitable stocking density for culturing of Indian butter catfish in grow‐out system.  相似文献   

20.
Dietary supplementation (0, 10, 20, 40, 60, 80 g kg?1) of a nucleotide source (NuPro®) was evaluated on growth, nutrient utilization, haemato‐immunological responses and resistance to experimental infection of Nile tilapia. Fish (2.63 ± 0.63 g) were fed experimental diets to satiation three times a day for 75 days. Feed intake increased linearly with increasing levels of NuPro® promoting higher weight gain (P < 0.05). Survival, feed conversion and protein retention were not affected. Following the growth trial, fish were challenged with Aeromonas hydrophila by intraperitoneal injection. Survival and innate immune responses (phagocytosis and lysozyme activity) were not significantly affected. However, among the haematological variables, thrombocyte, leucocyte and monocyte counts increased linearly (P < 0.05). The indirect measurement of digestibility in juvenile Nile tilapia (122.32 ± 11 g) indicated a linear decrease in protein (1.41%), dry matter (5.72%) and energy (4.10%) digestibility coefficients as dietary supplementation increased (P < 0.05). NuPro® showed to be a beneficial additive to be supplemented in diets for juvenile Nile tilapia, providing 32.8% increase in feed intake and 28.8% in weight gain, as well as in thrombocyte, leucocyte and monocyte counts in blood, possibly indicating a more efficient defence response in the highest dietary supplementation levels tested.  相似文献   

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