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1.
Different antibiotic‐based drugs are being used for the treatment of Aeromonas hydrophila infection in rainbow trout, and several studies emphasize the use of medicinal plants as immunostimulants for prophylactic measure against Aeromoniasis disease. However, therapeutic effects of aqueous methanolic extracts of tetra (Cotinus coggygria) against A. hydrophila in rainbow trout were not investigated. Four different concentrations of tetra extract (0 [control], 4, 8 and 12 mg/100 µl) and also two different positive control groups (florfenicol and doxycycline antibiotics) were administered orally using feeding needles to individual rainbow trout, Oncorhynchus mykiss of all experimental groups twice a day after intramuscular inoculation of A. hydrophila. The study period was for 10 days. On 0th, 3rd, 7th and 10th day, blood and tissues were collected from the fish and changes in humoral immune responses, haematology and immune‐related gene expressions were determined. In the study, superoxide radical production was decreased generally in all experimental groups except in 12 mg tetra and florfenicol treatments compared to control (p < .05). Lysozyme activity was generally decreased (p < .05), or no differences were observed in all experimental groups compared to the control. Myeloperoxidase activity was significantly increased in florfenicol‐treated fish group on 7th day (p < .05). Generally, myeloperoxidase activity showed an increase in almost all tetra‐treated groups. Haematological parameters increased but were not significantly high enough in treatments. Almost all immune‐related gene expressions were significantly enhanced on 3rd and 10th day of the study. Survival rate of 53.33% was found in control group. There were no significant differences in survival between control and 4 mg tetra‐treated group (p > .05). All the other groups' survival rate was significantly increased compared to control. The highest survival rate was found in florfenicol group (80%). In 12 mg tetra‐, doxycycline‐ and 8 mg tetra‐treated groups, survival rate was recorded as 74.44%, 70% and 70%, respectively. Our results suggest that tetra methanolic extract is an effective therapeutic remedy against A. hydrophila infection in rainbow trout at the dose of 24 mg/32.34 g body weight/day.  相似文献   

2.
Flavobacterium psychrophilum is responsible for significant economic losses in rainbow trout aquaculture. Antimicrobial treatment remains the primary means of control; however, there are limited choices available for use. The objectives of the study were therefore to determine the minimum inhibitory concentrations for erythromycin and florfenicol in selected F. psychrophilum isolates and to evaluate their clinical treatment efficacy in experimentally infected rainbow trout. All isolates tested had moderate susceptibility to florfenicol and erythromycin except one isolate, which had low susceptibility to erythromycin. Two isolates (one with moderate and one with low susceptibility to erythromycin) were used in an experimental infection trial. Rainbow trout juveniles were injected intraperitoneally with 108 cfu/fish and after mortality had begun, fish were given erythromycin‐ and florfenicol‐medicated feed at a rate of 75 mg kg?1 day?1 and 10 mg kg?1 day?1 fish body weight, respectively, for 10 consecutive days. The splenic F. psychrophilum load was determined using an rpoC quantitative PCR throughout the 30‐day trial. Relative to antibiotic‐free controls, erythromycin treatment significantly (p < 0.05) reduced mortality of rainbow trout juveniles infected with FPG101, even when treatment was initiated after clinical signs developed.  相似文献   

3.
The probiotic activity of 15 bacterial isolates that inhibit Saprolegnia parasitica in vitro was tested for the biocontrol of saprolegniosis in rainbow trout (Oncorhynchus mykiss Walbaum), adding the bacteria to tank water for 14 days at a concentration of 106 bacteria ml?1 water. Pseudomonas fluorescens LE89 and Pseudomonas fluorescens LE141 were effective in controlling experimental infection with S. parasitica since of the fish treated with LE89, 24.5% ± 16.27% (p < 0.05) became infected, as did 42.8% ± 8.41% (p < 0.05) of those treated with LE141. Given their protective effect when administered in water, their effect was also studied when administered in feed before and after experimental infection. Both bacterial isolates survived low pH levels and the action of bile, grew in skin and intestinal mucus, were resistant to several antibiotics and survived in feed; however, neither of the two isolates prevented S. parasitica infection when administered in feed.  相似文献   

4.
This study was designed to investigate the effects of restrictive and cyclical feeding on the growth parameters of dolphin cichlid (Cyrtocara moorii Boulenger, 1902). In the study, 300 dolphin cichlid with an initial average weight of 1.12 ± 0.23 g were placed in 15 aquariums (each of them were 60 L). The five experimental groups, were designed as; the control group (A), feeding until satiation twice a day for 90 days, starvation for 1 week (B), starvation for 2 weeks (C), starvation for 1 day/satiation for 3 days (D), starvation for 1 day/satiation for 1 day (E); and the study was carried out in three repetitions. At the end of the study, groups B, C and D showed partial compensatory growth. The highest weight gains and specific growth rates were observed in control group (A), followed by groups B, C and D (p > 0.05). The lowest weight gain was observed in group E (p < 0.05). The feed conversion ratio did not show any significant difference between the groups (p > 0.05). In terms of feed consumption ratio, Control, C and D groups consumed similar amounts of feed (p > 0.05), while B and E groups consumed less feed (p < 0.05) than the other groups.  相似文献   

5.
The influence of timing of extended photoperiods on growth and maturity of brook trout was investigated in a 112‐day experiment. The fish with mean initial weight of ~192 g were reared under four light regimes: one control group with natural ambient photoperiod and three groups exposed to an 18L:6D regime initiated at days 1, 23 or 46 of the growth trial. Light‐emitting diodes, with intensity of 250–1000 lux, depending on the distance from the light source, were used for extending light periods. There was a positive effect of prolonged day length on fish growth (p < 0.05), and a delay in gonad development and sexual maturity. Significantly higher numbers of sexually mature fish were found among controls groups, regardless of sex. Survival rate was not affected by light regime. This study demonstrated that the short‐term expansion of the photo period delayed maturation and increased the growth rate of brook trout.  相似文献   

6.
The present study was conducted to investigate the effects of Bacillus pumilus on the growth performance, innate immunity and digestive enzymes of the giant freshwater prawn, Macrobrachium rosenbergii. Prawns (mean weight: 1.81 ± 0.01 g) were fed different levels of B. pumilus at doses of 0, 1 × 107, 1 × 108 and 1 × 109 CFU/g to produce one control group and three experimental groups (G1, G2 and G3), respectively. After a 60‐day experimental feeding period, the results showed that the final weight, weight gain rate (WGR) and specific growth rate (SGR) were significantly higher in experimental groups than in the control (p < 0.05), whereas these improvements did not differ significantly (p > 0.05) among experimental groups. The improvements in phagocytic activity, respiratory burst (RBs) activity and the activity of catalase (CAT), nitric oxide synthase (NOS) and acid phosphatase (ACP) were significantly higher in G2 and G3 than in the control and G1 (p < 0.05). Further, the activity of CAT, NOS and ACP significantly increased with an increase in the dietary level of B. pumilus (p < 0.05). The activity of phenoloxidase (PO) in G3 was significantly higher than that in the control (p < 0.05). The activity of amylase was significantly higher in the groups G2 and G3 than that in the control group. G3 improved the activity of protease compared with the control (p < 0.05). In conclusion, the results of this study indicated that the potential use of B. pumilusat a dose of 1 × 108 CFU/g feed could improve the growth, immunity and digestive enzymes of M. rosenbergii.  相似文献   

7.
The current study was conducted to evaluate the effect of dietary soy isoflavones (SI) on growth performance, antioxidant status, immune response and resistance to Aeromonas hydrophila in juvenile grass carp (Ctenopharyngodon idella). Six diets were formulated to contain 0 (control), 10, 50, 100, 500 or 1,000 mg SI per kg feed. Each diet was randomly allotted to triplicate net cages, and each net cage was stocked with 30 fish. The fish were fed one of the experimental diets to satiation twice per day for 60 days. The results showed that the WGR and DGC of the 500 mg/kg SI‐supplemented group were significantly higher than those of the non‐SI‐supplemented group (p < .05). Serum LZM and IgM activities in the SI‐supplemented groups were improved compared to the control group. SOD and GSH‐Px levels of fish fed the diet containing 500 mg/kg SI were significantly enhanced compared to those of fish fed the control diet (p < .05). Additionally, serum CAT, GSH‐Px and AKP activities in 50, 100 and 500 mg/kg SI‐supplemented groups were significantly higher than that in the control group (p < .05). The expression of most immune‐related genes (including IFN‐γ2, TNF‐α, M‐CSF2, IL‐6, IL‐12p40 and IL‐4) was significantly affected by dietary supplementation of SI. The group fed with 500 mg/kg SI had the highest 7‐day cumulative survival rate after challenge test (p < .05). The current results revealed that dietary inclusion of SI could improve the immune response and resistance against A. hydrophila and the supplementation level is suggested to be 500 mg/kg diet.  相似文献   

8.
The present study investigated the effects of combination of dietary Bacillus subtilis and trans‐cinnamic acid on serum biochemical parameters, innate immune responses and resistance of rainbow trout, Oncorhynchus mykiss to Yersinia ruckeri. Six experimental groups of fish with mean weights of 20.58 ± 0.35 g were used in the study. Five experimental groups of fish were fed diets containing Bacillus subtilis (107 per gram) or a mix of the Bacillus subtilis (BS) and trans‐cinnamic acid (25 mg/kg‐25trcBS, 50 mg/kg‐50trcBS, 75 mg/kg‐75 trcBS, 150 mg/kg‐150 trcBS), whereas an additive‐free basal diet served as the control (Cont). In this study, an increase was observed in granulocyte percentage, respiratory burst activity, phagocytic activity, phagocytic index, myeloperoxidase activity and total antiprotease activity especially in fish fed with mix of the BS and trans‐cinnamic acid‐supplemented diets (p < .05). Moreover, at the end of the 20‐day challenge period the survival rates and antibody titre (p < .05), and relative per cent survival were higher in the BS group and all trcBS groups compared with control group. As a conclusion, the results in the present study show that feeding rainbow trout with diets containing a mix of B. subtilis and trans‐cinnamic acid over a 60‐day period might be sufficient for improving fish immune responses and disease resistance against Y. ruckeri.  相似文献   

9.
Lactic acid bacteria (LAB) have a crucial role in inorganic selenium metabolism as well as their known desirable effects on fish. In this study, the synergistic effects of dietary sodium selenite and Pediococcus acidilactici on growth performance, intestinal bacterial counts, selenium bioavailability, hepatic antioxidant enzyme thioredoxin reductase activity and hepatic glycolytic enzyme activity that is hexokinase, phosphofructokinase and pyruvate kinase, and non‐specific immune response such as serum lysozyme and complements C3, C4 and ACH50 activity in rainbow trout (Oncorhynchus mykiss) were investigated. Thus, a 3 × 3 factorial design experiment was conducted with nine purified diets including three levels of sodium selenite (0, 1 and 2 mg/kg) and three levels of P. acidilactici (0, 7 and 9 log CFU/g). After 8 weeks of feeding, weight gain and specific growth rate were increased by increasing dietary sodium selenite and P. acidilactici levels compared to control (p < .05), whereas feed conversion ratio and condition factor was decreased by increasing dietary sodium selenite and P. acidilactici amounts in comparison with control (p < .05). Survival rate was not significantly affected among the experimental treatments (p > .05). Total cultivable bacterial populations after 4 and 8 weeks of the feeding trial were not significantly different among the dietary treatments, while LAB levels were higher in P. acidilactici‐fed groups than in control and selenium‐fed groups (p < .05). Selenocysteine, methylselenocysteine and selenomethionine levels in the intestine of rainbow trout were increased by increasing the sodium selenite and P. acidilactici levels (p < .05), and selenocysteine was found the most selenium species in the trout intestine. The quantity of total selenium in the whole body, intestine, blood, liver and muscle of rainbow trout were increased by increasing the amounts of sodium selenite and P. acidilactici compared to control (p < .05). Hepatic thioredoxin reductase and hexokinase activity were increased by increasing dietary selenium and P. acidilactici levels in comparison to control (p < .05), whereas phosphofructokinase and pyruvate kinase activity in the liver of rainbow trout were not significantly different between the dietary treatments. Serum lysozyme, complements C3, C4 and ACH50 activity were enhanced by increasing dietary selenium and P. acidilactici levels compared to control (p < .05). The most synergistic effects of dietary supplements on growth and metabolism of rainbow trout were obtained at 2 mg/kg sodium selenite and 7 log CFU/g P. acidilactici. The findings revealed the synergistic effect of dietary selenium and P. acidilactici on growth and metabolism in rainbow trout (O. mykiss).  相似文献   

10.
Diets containing deoxynivalenol (DON) were fed to rainbow trout Oncorhynchus mykiss (Walbaum) for 4 weeks followed by experimental infection (intraperitoneal) with Flavobacterium psychrophilum (4.1 × 106 colony‐forming units [CFU] mL−1). Mortality of rainbow trout fed either 6.4 mg kg−1 DON or trout pair‐fed the control diet was significantly reduced (P < 0.05) in comparison with trout fed the control diet to apparent satiation (<0.1 mg kg−1 DON). In a second experiment, trout were fed one of three experimental diets; a control diet, a diet produced with corn naturally contaminated with DON (3.3 mg kg−1 DON) or a diet containing purified DON (3.8 mg kg−1); however, these fish were not experimentally infected. The presence of DON resulted in significant reduction (P < 0.0001) in feed intake as well as weight gain after 4 weeks. Respiratory burst of head‐kidney leucocytes isolated from rainbow trout fed diets containing purified DON (3.8 mg kg−1) was significantly higher (P < 0.05) at 35 day post‐exposure compared with controls. The antimicrobial activity of DON was examined by subjecting F. psychrophilum in vitro to serial dilutions of the chemical. Complete inhibition occurred at a concentration of 75 mg L−1 DON, but no effect was observed below this concentration (0–30 mg L−1).  相似文献   

11.
In this study, we used artificial insemination to generate hybrid groups of fish [MC‐F1(MA♀×CA♂) and MC‐F2(MC‐F1♀×♂)] by intergeneric crosses of Megalobrama amblycephala (MA) and Culter alburnus (CA); sequential backcrosses [CAM‐B1 (CA♀×MC‐F1♂) and MCC‐B1 (MC‐F1♀×CA♂)] were also performed. All these hybrids showed high rates of fertilization, hatching and survival (p > 0.05). For genetic traits, compared with those of the M. amblycephala and C. alburnus parental lines (Table 1), the fertilization rate, hatching rate and 7‐day survival rate of MC‐F1(MA♀×CA♂), MC‐F2(MC‐F1♀×♂), CAM‐B1 (CA♀×MC‐F1♂) and MCC‐B1 (MC‐F1♀×CA♂) by artificial insemination exhibited similar high rates (p > 0.05). The morphology of the four hybrids MC‐F1/F2, CAM‐B1 and MCC‐B1 were intermediate between those of their parents. Compared with their parents of MA and CA, weight gain rate (WG), specific growth rate (SGR) and protein efficiency ratio (PER) of hybrids MC‐F1/F2, CAM‐B1 and MCC‐B1 were significantly (p < 0.05) increased and feed conversion ratio (FCR) was significantly (p < 0.05) decreased after 3 months feeding. Moreover, protein content of muscle for MC‐F1/F2, CAM‐B1 and MCC‐B1 was significantly (p < 0.05) higher and carbohydrate content of muscle was significantly (p < 0.05) lower than their parents. The females and males of the four hybrids had normal gonadal development. In this study, we successfully generated intergeneric and backcross hybridization lines with fertile potential among fish of the Cultrinae subfamily and these hybrids had obvious heterosis in terms of growth performance, feed utilization and muscle quality.  相似文献   

12.
Flavobacterium psychrophilum, the causative agent of bacterial cold‐water disease (BCWD) in freshwater‐reared salmonids, is also a common commensal organism of healthy fish. The virulence potential of F. psychrophilum isolates obtained from BCWD cases in Ontario between 1994 and 2009 was evaluated. In preliminary infection trials of rainbow trout juveniles, significant differences (0% to 63% mortality) in the virulence of the 22 isolates tested were noted following intraperitoneal injection with 108 cfu/fish. A highly virulent strain, FPG 101, was selected for further study. When fish were injected intraperitoneally with a 106, 107 or 108 cfu/fish of F. psychrophilum FPG 101, the 108 cfu/fish dose produced significantly greater mortality (p < 0.05). The bacterial load in spleen samples collected from fish every 3 days after infection was determined using rpoC quantitative polymerase chain reaction amplification and by plate counting. Bacterial culture and rpoC qPCR were highly correlated (R2 = 0.92); however, culture was more sensitive than the qPCR assay for the detection of F. psychrophilum in spleen tissue. Ninety‐seven per cent of the asymptomatic and the morbid fish had splenic bacterial loads of <2.8 log10 gene/copies and >3.0 log10 gene copies/reaction, respectively, following infection with 108 cfu/fish.  相似文献   

13.
The effect of rapeseed meal (RM) and Aspergillus oryzae fermented rapeseed meal (RM‐Koji) on red sea bream (Pagrus major) was examined. Three groups of fish (initial weight, 4.5 ± 0.02 g) were fed a basal diet (RM0) and two test diets where half of fishmeal was replaced by RM (RM50) and RM‐Koji (FRM50) for 56 days. The obtained results showed that fish fed RM0 and FRM50 exerted significantly higher growth performance, feed utilization and haemoglobin level but lower triglyceride and cholesterol than RM50 group (p < 0.05). Interestingly, except of antiprotease activity, all the immune parameters including lysozyme, respiratory burst (NBT) and bactericidal activities were significantly increased in fish fed RM0 and FRM50 diets compared to RM50 diet (p < 0.05). In addition, malondialdehyde and reactive oxygen metabolites were significantly reduced in RM0 and FRM50 groups over RM50 group (p < 0.05). The present results suggest that fermented RM induced better growth performance and immune responses than feeding red sea bream with non‐fermented RM and both RM and RM‐Koji improved the antioxidative status of fish, making RM‐Koji an interesting candidate as a functional feed for aquatic animals.  相似文献   

14.
This study was done to assess the effect of the colouration of the red zebra cichlid (Maylandia estherae), using beet root red (Beta vulgaris ruba) and henna (Lawsonia inermis). The fish with an average weight of 1.21 ± 0.69 g was placed in 12 aquariums. Fifteen fish were placed in each aquarium. The fish were fed with diets which were without carotenoid supplement (AK), containing astaxanthin (AA), beet root red (AP) and henna (AI). Except the AK, each group contained 50 mg/kg carotenoid additives. As a result of the experiment, total carotenoid values between groups were not significant (p > .05). The redness (a*) value of groups was significant (p < .05), and the values of brightness (L*) and yellowness (b*) were not significant (p > .05). Samples were kept in the freezer at ?20°C for 120 days to see whether the fish kept their colour. All groups decreased compared with the 50th day. This difference in groups except the AP was significant (p < .05). The FCR, SGR and weight gain% was not significant (p > .05). The survival was 97.28%, and it was the same in all groups. The study concluded that natural carotene sources with lower costs had similar effects with astaxanthin.  相似文献   

15.
In this study, the effect of combined feeding Black Sea trout (Salmo trutta labrax) broodstock with commercial feed and mealworm larvae (Tenebrio molitor) for 50 days before the breeding period in order to evaluate the gamete quality. While the control group was fed with commercial feed, mealworm larvae were given as an additional protein source 2 days a week and 3 days a week to the experimental groups formed from female and male individuals. In addition to the growth parameters, the number of eggs (number/individual) and the egg diameter (mm), sperm volume (ml), density of spermatozoa (×109 cell/ml), total motility (%), progressive motility (%) and average curvilinear velocity (VCL, µm/sec) values were determined. At the end of the study, the highest live weight gain was found as 46.2 g in the control group of male. The egg diameters were 4.3 ± 1.8 mm and 4.5 ± 1.4 mm in the worm treatment groups fed twice and three times with mealworm respectively. As a result, it was determined that feeding fish with mealworm larvae as an addition to the commercial diet in female individuals did not affect the amount of eggs (p > .05), but the egg diameters were significantly smaller in the control group than the mealworm groups (p < .05). In spermatological characteristics, only the amount of sperm was different between the groups (p < .05); all other parameters were found to be similar to each other with no statistical differences (p > .05).  相似文献   

16.
Using plant extracts as immunostimulants in aquaculture has prove effectiv in resisting infectious disease, in addition to being safe and inexpensive. The present study is concerned about the prospective mode of action of using lesser galangal extract (Alpinia officinarum) encapsulated into amine surface functionalized mesoporous silica nanoparticles (MSN) in order to elevate the immune status of rainbow trout (Oncorhynchus mykiss). Fish were randomly divided into 6 groups and fed for 4 weeks with commercial diets supplemented with 0% (control), 0.5% and 1.5% of lesser galangal extract, and with previous concentrations encapsulated with MSN (0.5% + MSN, 1.5% + MSN) and MSN (without extract). The effects of the feeding trial on the innate humoural immune parameters (total protein, myeloperoxidase content, lysozyme antiproteases and bactericidal activities) in rainbow trout were examined. Also, the influence of dietary supplement on some immune‐related genes in rainbow trout head kidney (TNF, IL‐8, IL‐1b, LYZ2 and CD4) after challenge with Yersinia ruckeri was examined. The results revealed enhancement in immune parameters in all treatment groups compared to the control, especially in the fish group fed with 1.5% + MSN which showed the highest significant difference (p < .05) in total protein, lysozyme and antiproteases activities. Also, feeding lesser galangal extract encapsulated into MSN led to an increase in myeloperoxidase content and bactericidal activity. An improvement in the expression of immune‐related genes has been recorded in fish groups fed doses of lesser galangal extract and lesser galangal extract encapsulated into MSN compared to the control or to the group fed with MSN only. Particularly, the group fed with 0.5% + MSN showed a significant up‐regulation in most of the immune‐related genes. The current investigation supports using lesser galangal extract encapsulated into MSN in fish diets as a supplement to enhance the immune response of rainbow trout and elevate its resistance to infectious diseases.  相似文献   

17.
This study evaluated effects of fishmeal replacement by cottonseed meal protein hydrolysate (CPH) on growth, antioxidant and immunity of Megalobrama amblycephala and its resistance to Aeromonas hydrophila. Fish (average weight: 38.66 ± 0.08 g) were divided into five groups and fed with five isonitrogenous (320 g/kg crude protein), isolipidic (70 g/kg crude fat) and isocaloric (17.8 MJ/kg gross energy) diets replacing fishmeal with 0%, 1%, 3%, 5% and 7% CPH, respectively. The control diet contained 60 g/kg fishmeal. Final weight and weight gain of fish fed 5% and 7% CPH were significantly lower than that of fish fed control diet (p < 0.05). 3% CPH significantly increased total protein, globulin, acid phosphatase, C3 and C4 contents of plasma and total‐superoxide dismutase and catalase activities of liver (p < 0.05), as well as upregulated the antimicrobial peptides 1 and 2 (Leap‐1 and Leap‐2) expression levels in liver and spleen (p < 0.05). After challenge, the lowest mortality was observed in fish fed 3% CPH, and it was significantly lower than that in fish fed the 7% CPH (p < 0.05). In conclusion, dietary fishmeal replacement by 3% CPH could increase antioxidative capacity, as well as enhance immunity of fish.  相似文献   

18.
The study was to examine the effects of dietary L. aspera on growth performance, physio-metabolic response and health status of Rita rita fish reared in tanks for 60 days. Six experimental diets were formulated containing 0 g/kg, 3 g/kg, 6 g/kg, 9 g/kg and 12 g/kg L. aspera and designated as D0, D3, D6, D9 and D12 respectively. The inclusion of L. aspera at graded levels resulted in significantly varying effects on growth performance where the weight gain (%), specific growth rate (SGR) and feed conversion efficiency (FCE) were significantly higher (p<0.05) in D6 and D9 groups than others. The protease and amylase activities were elevated in L. aspera supplemented groups than the control group (p<0.05), whereas lactate dehydrogenase, malate dehydrogenase and serum transaminase enzyme activities were significantly reduced with the increasing level of L. aspera and comparatively higher activities of the respective enzymes were found in the control group. The activities of oxidative stress enzymes were significantly higher (p<0.05) in the D9 group and lower in control. The blood glucose level significantly decreased with the increasing level of L. aspera in the experimental diets. The L. aspera supplemented fish had significantly higher liver glycogen, serum protein, albumin and globulin than control group. Red blood cell count was significantly higher (p<0.05) in D6-D12, whereas white blood cell count and haemoglobin content were significantly higher (p<0.05) in D6 and D9 groups. Regression analysis showed that L. aspera at the level of 7.3–7.9 g/kg is optimum for better growth and feed efficiency.  相似文献   

19.
An 84‐day feeding trial was carried out to evaluate the effects of aqueous Psidium guajava leaf extract (PGE) on growth, intestinal morphology, physiology, immune response and susceptibility of Oreochromis niloticus to Aeromonas hydrophila. Diets containing 0% (P0), 0.25% (P1), 0.50% (P2), 0.75% (P3) and 1.00% (P4) PGE were fed to triplicate groups of fish (mean weight; 1.32 ± 0.04 g) for 84 days. After the 84‐day feeding trial, test fish were injected with pathogenic A. hydrophila and then fed for 14 days. More feed were consumed in groups of fish fed PGE‐treated diets and resulted in significantly higher weight gain and feed intake. Incidentally, there was an increase in the calculated area of absorption of fish fed PGE diets, as accounted for by marginally higher villi length and width. Antioxidant and immune response were improved with PGE inclusion in diets as total protein, superoxide dismutase, glutathione peroxidase and glutathione S‐transferase significantly increased (p < 0.05) in fish fed PGE diets. Results of the challenge test with A. hydrophila revealed that the highest mortality (100%) was recorded in P0. This study revealed that inclusion of P. guajava extract in the diet of O. niloticus improved growth, nutrient utilization, immune system and survival of O. niloticus fingerlings.  相似文献   

20.
This study investigated the effects of a synbiotic Lacto Forte on growth performance, haemato‐immunological responses, plasma bactericidal capacity, histological profiles and resistance of Oreochromis niloticus to Pseudomonas fluorescens. The experimental fish were divided into three groups; two of them (T1 and T2) were given Lacto Forte incorporated diets at increasing level (0.7 and 1.5 g/kg, respectively) and an additive‐free basal diet served as the control (T0) for 30 and 45 days. At the end of the feeding trial, a challenge was performed using a virulent strain of P. fluorescens and mortalities were recorded over an additional 14‐days period. The results showed that Lacto Forte has a pronounced effect on haematological and growth performance parameters at 1.5 g/kg rather than 0.5 g/kg (p < 0.05). Plasma lysozyme, proteases, antiproteases and bactericidal capacity were significantly enhanced (p < 0.05) in Lacto Forte‐treated groups, particularly after 45 days of supplementation. Long‐term supplementation with Lacto Forte (1.5 g/kg) induced degenerative changes in the liver, spleen and intestine. Additionally, a significant increase (p < 0.05) in survival rates were found in Lacto Forte‐treated groups compared to the control one 14 days post‐challenge. As a result, Lacto Forte fortifies tilapia immune response and can be used as a surrogate for antibiotics to control P. fluorescens.  相似文献   

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