首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
The use of prebiotics and probiotics as feed supplements that improve efficiency of intestinal bacteria is becoming de rigueur in animal husbandry in many regions worldwide. We tested the effects of a commercial probiotic (Biogen®) containing allicin, high unit hydrolytic enzyme, Bacillus subtilis spores and ginseng extracts on survival, growth, carcass composition and feed cost/benefit in rabbitfish Siganus rivulatus. Fifteen net cages (100 × 100 × 40 cm; L × W × H) were stocked with 10 juvenile rabbitfish (10.3 g per fish) each and placed in a large rectangular tank and offered feed at 4% body weight daily. Cages were offered one of five isonitrogenous and isocaloric diets containing 0, 1, 2, 3 and 4 g kg−1 probiotic at three replicates per treatment for 98 days. Fish in all cages were weighed at 2‐week intervals and feed regimen was adjusted accordingly. Rabbitfish offered the control diet exhibited lower growth and feed utilization than all experimental treatments. There was no effect of probiotic inclusion level on survival but growth was better at all inclusion levels than in the control. No significant differences (P > 0.05) in growth were observed among fish groups fed various levels of the probiotic. Carcass composition was not affected by dietary probiotic inclusion. Ultimately, when all variables are considered, Biogen® inclusion to diets appears to reduce feed cost per unit growth of rabbitfish.  相似文献   

2.
The present study was performed to investigate the effects of a commercially available probiotic product (compound probiotic) containing Bacillus subtilis 7.0 × 109 CFU g?1, Bacillus licheniformis 3.0 × 109 CFU g?1, Lactobacillus spp. 5.0 × 108 CFU g?1 and Arthrobacter spp. 1.0 × 108 CFU g?1 on the growth performance, non‐specific immunity and protection against Vibrio harveyi infection in cobia (Rachycentron canadum). Fish were fed diets containing six graded levels of compound probiotic (0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 g kg?1) for 8 weeks. The results showed that the survival rate ranged from 81.1% to 84.4% with no significant difference among dietary treatments (P > 0.05) after feeding experiment. Dietary compound probiotic significantly increased the specific growth rate (SGR), serum lysozyme, alternative complement pathway (ACP) activity, phagocytosis percentage (PP) and respiratory burst activity of head‐kidney macrophages of cobia. Moreover, feeding of supplemented diets containing compound probiotic resulted in significantly lower mortality against the pathogens Vibrio harveyi compared with the control group. To elevate the growth and immune resistance ability of cobia, an optimal dose of dietary compound probiotic administration determined by second‐order polynomial regression analysis was 3.3 g kg?1, on the basis of the SGR and mortality after challenge with V. harveyi.  相似文献   

3.
The aim of this study was to evaluate the effect of dietary supplementation with the autochthonous probiotic bacteria Bacillus cereus on growth performance, haematological parameters and survival of tambaqui (Colossoma macropomum). Tambaqui fingerlings (0.94 ± 0.02 g) were fed for 120 days the following diets: basal (without probiotic) and three supplemented diets (4.2 × 104, 3.9 × 106 and 3.3 × 108 CFU/g). Growth performance and haematological parameters were evaluated every 30 days. Thereafter, fish were challenged against Aeromonas hydrophila and survival was evaluated. Probiotic B. cereus improved weight and length gains (p < 0.05), and increased neutrophils and thrombocyte counts (p < 0.05) in tambaqui supplemented with 3.9 × 106 CFU/g diet. Challenged fish fed unsupplemented diet presented the lowest survival rate (33.4%) while fish fed diets supplemented at 4.2 × 104, 3.9 × 106 and 3.3 × 108 CFU/g B. cereus had 88.8%, 80.5% and 80.5% relative per cent survival respectively. These results demonstrated that B. cereus supplemented as probiotics to C. macropomum for 120 days improved physiological and haematological responses, leading to enhanced survival in this fish species.  相似文献   

4.
A 2 × 3 factorial design with triplicates examined the interaction between dietary inorganic phosphorus (IP) and phytase on growth, mineral utilization and phosphorus (P) mineralization in juvenile red sea bream. The treatments were three levels of dietary IP supplementation at 0, 2.5 and 5 g kg?1, either without or with phytase supplementation [2000 FTU kg?1; phytase unit is defined as the amount of enzyme activity which liberates 1 micromol of inorganic phosphorus per minute at pH 5.5 and 37 °C at a substrate concentration (sodium phytate) of 5.1 mmol L?1]. Juvenile red sea bream (IBW = 1.3 g ± 0.1) were stocked twelve fish per tank and fed for 50 days. Growth and feed efficiency were significantly (P < 0.05) enhanced by both dietary P and phytase supplementation. Feed intake and survival rate were not significantly affected by the dietary treatments. Both dietary IP and phytase supplementation significantly increased plasma IP and Mg levels. Concentration of vertebral mineral and scale P was significantly increased by both dietary treatments. A skeletal malformation syndrome of scoliosis occurred in fish fed both non‐IP and non‐phytase supplemented diet. Interaction between main dietary effects was detected for vertebral Zn, scale P and whole‐body ash and Mg content. With regard to growth and other examined productivity traits, phosphorus requirement of juvenile red sea bream can be met if supplemented with 2000 FTU phytase kg?1 or in the absence of phytase, by dietary inclusion of 2.5–5 g kg?1 of IP.  相似文献   

5.
The present study investigates the effects of dietary commercial Bacilli probiotic (Bacillus subtilis and Bacillus licheniformis) on the growth performance, feed efficiency, body composition and immune parameters of Litopenaeus vannamei. The L. vannamei postlarvae were supplied and acclimated (in 500‐L tanks) to laboratory conditions for 14 days. The shrimps were fed with diets containing 1 × 104 and 1 × 108 CFU/g probiotic Bacilli for 60 days. At the end of the feeding trial, growth performance parameters, body composition, serum biochemical parameters and the hemocytes count were evaluated. Shrimps fed diets supplemented with 1 × 104 and 1 × 108 CFU/g probiotic Bacilli showed improved weight gain, total length, specific growth rate, FCR and survival compared with the control group. The body composition studies revealed higher dry matter, crude protein and ash in shrimps fed with 1 × 104 and 1 × 108 CFU/g probiotic Bacilli. Also, dietary administration of 1 × 104 and 1 × 108 CFU/g probiotic Bacilli decreased serum glucose and cortisol levels. However, significantly increased total protein, lysozyme and hemocyte cell count were noticed in shrimps fed 1 × 104 and 1 × 108 CFU/g probiotic Bacilli. In general, the findings of this study proved that oral administration of 1 × 104 and 1 × 108 CFU/g commercial probiotic Bacilli improved growth performance, feed utilization and immune parameters in whiteleg shrimp (Litopenaeus vannamei).  相似文献   

6.
The effect of dietary administration of Lactococcus lactis MM1 and Enterococcus faecium MM4, two strains of lactic acid bacteria isolated from the gut of juvenile grouper Epinephelus coioides, on the growth, feed utilization, digestive enzymes and immune response of juvenile E. coioides was evaluated. The fish were fed for 60 days with three different diets: control diet (without probiotic), diet P1 supplemented with 1.0 × 108 CFU g?1L. lactis or diet P2 with 1.0 × 108 CFU g?1E. faecium. Although growth and feed intake decreased slightly, significant improvement of feed utilization was observed in fish fed diet P1 and diet P2 for 60 days. The hepatopancreatic protease activities in the two probiotic treatments were significantly higher than that in the control. The phagocytic activity, serum superoxide dismutase activity and complement component 4 (C4) and IgM levels were not significantly affected by diet P1 and diet P2. Serum complement component 3 (C3) levels in the two treatments were significantly higher than that in the control. Significant increased serum lysozyme activity was observed in fish fed the diet P1, while significant decreased lysozyme activity was observed in fish fed the diet P2 compared with the fish fed the control diet. There was a significant interaction effect between diet and administration date for the complement C4. The study demonstrates potential for L. lactis MM1 and E. faecium MM4 to improve the feed utilization and modulate the immune function in E. coioides.  相似文献   

7.
Intensive fish farming has resulted in an increased concern for disease outbreaks. Probiotic use is one of the strategies being developed to improve fish health and productivity. Measures of probiotic colonization, growth performance, haematological characteristics and parasite load were used to evaluate the effect of diets supplemented with Enterococcus faecium on growth and health of Arapaima gigas juveniles. A completely randomized design with four treatments (diet with E. faecium at 1 × 106 CFU/g and 1 × 108 CFU/g, control diet and diet with the culture medium MRS) and three replicates was used. Ninety‐six Arapaima juveniles were distributed in 12 cages fed with the specified diet for 68 days. Colonization of the intestinal tract by lactic acid bacteria reduced the total number of heterotrophic bacteria in fish fed with probiotics compared to controls. Fish fed a supplemented diet containing 1 × 108 CFU/g presented higher values of weight gain, survival and fish growth uniformity, and lower values of feed conversion ratio. The prevalence of Trichodina sp. could have affected the survival of fish in the control group. Reduction in parasite load and an increase in haematocrit, the number of erythrocytes, thrombocytes, neutrophils and monocytes were also observed in fish fed the diet containing 1 × 108 CFU/g. Enterococcus faecium presented a probiotic effect in A. gigas juveniles and can be recommended for use at a concentration of 1 × 108 CFU/g to modify the gut microbiota, improve growth performance and haematology and reduce parasitic load.  相似文献   

8.
The present study was conducted to determine the effects of Bacillus subtilisKADR1 and its subcellular components on immunity and disease resistance in Labeo rohita against Aeromonas hydrophila infection. Fish were fed diet containing different concentrations of live bacterial cells (DI‐106, DII‐108 and DIII‐1010 CFU/g) and another group of fish were immunized intraperitoneally with cellular components (WCPs, CWPs and ECPs) of Bacillus subtilisKADR1. After 4 weeks of trial, fish were challenged intraperitoneally with Aeromonas hydrophila cell suspension and survival percentage was recorded. Significantly higher post‐challenge survivability was recorded in fish groups fed 108 CFU/g of KADR1 (80.24%; RPS = 75.76%) or immunized with WCPs (77.77%; RPS = 72.73%), compared with the control (18.51%). Analysis of immunological parameters viz. serum lysozyme, phagocytosis, serum total protein, respiratory burst, serum IgM levels, superoxide dismutase and alternative complement pathway activity reflected significant enhancement (p < .05) of immune response in fish fed 106, 108 and 1010 CFU/g of live cells, or immunized with cellular components of Bacillus subtilisKADR1, with the highest values were observed DII fed group, followed by the group immunized with WCPs. Our results suggest that dietary administration of Bacillus subtilisKADR1 at 108 CFU/g can effectively enhance the immune responses and disease resistance in Labeo rohita against Aeromonas hydrophila.  相似文献   

9.
A feeding experiment was conducted to determine the dietary calcium (Ca) requirement for juvenile hybrid tilapia, Oreochromis niloticus × O. aureus reared in nature water. Purified diet supplemented with 0, 1, 2, 3, 4, 5, 7 and 10 g Ca kg−1 diet providing of 0.6, 1.6, 2.6, 3.7, 4.7, 5.5, 7.5 and 10.7 g Ca kg−1 diet, respectively, were fed to tilapia (mean initial weight: 0.52 ± 0.01 g, n = 3) for 8 weeks. Each diet was fed to three replicate groups of fish in a closed, recirculating fresh water rearing system. The rearing water contained 27.1–33.3 mg L−1 Ca. The tilapia fed the diets supplemented with ≥3.7 g Ca kg−1 had significantly (P < 0.05) higher weight gain, when compared with fish fed the diet with ≤1.6 g Ca kg−1. Fish fed the unsupplemented control showed significantly lower weight gain when compared with the other groups (P < 0.05). Bone Ca concentration was highest in fish fed the diets with ≥4.7 g Ca kg−1, intermediate in fish fed the diet with 2.6 g Ca kg−1 and lowest in fish fed the control diet. Scale Ca concentration was higher in fish fed the diets with ≥3.7 g Ca kg−1 than in fish fed the diets with ≤2.6 g Ca kg−1. Serum alkaline phosphatase activity was 36% increased in fish fed the diets with ≥2.6 g Ca kg−1 than fish fed the diets with <1.6 g Ca kg−1. Analysis by broken‐line regression of weight gain, bone and scale Ca concentrations indicated that the adequate dietary Ca concentration for tilapia in water containing 27.1–33.3 mg Ca L−1 was 3.5, 4.3 and 4.2 g Ca kg−1 diet, respectively, supplied as Ca‐lactate.  相似文献   

10.
We evaluated the effects of Bacillus cereus, as an additive in water and feed, on the gut microbiota and immunological parameters of Nile tilapia (Oreochromis niloticus) fingerlings. Experiments were performed in tanks and net cages respectively. Experiment 1: Tilapia were housed in tanks for 42 days, and B. cereus was added to the water at 1.0 × 104 cfu mL?1 (Treatment 1) and 1.0 ×105 cfu mL?1 (Treatment 2) weekly. For the control, no probiotic was added. Experiment 2: Tilapia were housed in cages for 42 days, and the feed was supplemented with B. cereus at 1.0 × 107 cfu g?1 (Treatment 1) and 1.0 × 108 cfu g?1 (Treatment 2) weekly. For the control, no probiotic was added. Each treatment contained three replicates, with 50 male tilapias per replicate. The fish from the probiotic treatments in both tank and cage experiments had significantly higher serum lysozyme and peroxidase activities than the control. In the cage experiment, alkaline phosphatase and total superoxide dismutase activities in tilapia were significantly higher in probiotic treatments compared with the control. The results of polymerase chain reaction‐denaturing gradient gel electrophoresis showed that B. cereus supplementation in the feed and water affected the autochthonous gut bacteria community of tilapia and stimulated various potentially beneficial bacteria. Therefore, B. cereus, as a water or feed additive, could enhance the immune status and affect the gut microbiota of tilapia. Bacillus cereus was more effective as a feed supplement rather than a water additive for enhancing the immune status of tilapia.  相似文献   

11.
The objective of this study was to evaluate the effect of dietary supplementation of a probiotic bacterium, Bacillus subtilis, on the growth, immune response and antioxidant activities of shrimp (Litopenaeus vannamei). Shrimps with an average initial weight of 2.11±0.17 g were randomly assigned to four groups with three replicates. The control group was fed a basal diet, and three treated groups were fed diets supplemented with B. subtilis at doses of 1 × 104, 5 × 104 and 10 × 104 colony‐forming unit (CFU) g?1 feed respectively. After 40 days of culture, 10 shrimps from each replicate were taken randomly for the determination of immune response and oxidization resistance indices. The results showed that the shrimps fed with B. subtilis at a dose of 1 × 104, 5 × 104 CFU g?1 feed showed significantly better growth than that of the control diet. The phenoloxidase activities showed a tendency to increase with an increased dose of B. subtilis in diets but there was no significant difference among the three treated groups. In addition, phenoloxidase activities were found to be significantly higher (P<0.05) in the groups treated with B. subtilis than that of the control group. Shrimps treated with 5 × 104 CFU g?1 feed probiotic bacterium showed the highest lysozyme activity and it was significantly higher (P<0.05) than the other groups. However, there was no significant difference in acid phosphatase and alkaline phosphatase activity across all the groups. The total antioxidant capacity, superoxide dismutase and glutathione peroxidase activities in the probiotic‐treated groups were significantly increased (P<0.05) as compared with the control groups. Both maleic dialdehyde concentration and superoxide anion activities in the probiotic‐treated groups were significantly lower (P<0.05) than those of the control. The probiotic did not affect the nitric oxide synthase and the catalase activity in any of the control and treated groups. These results indicated that the probiotic B. subtilis could significantly promote the growth rate of shrimp by increasing the immune function and antioxidant capacity. The most effective dose of B. subtilis in the diet was 5 × 104 CFU g?1 feed.  相似文献   

12.
The effects of dietary astaxanthin supplemented at 0, 40, 80 or 150 mg astaxanthin kg−1 on growth, survival, moult frequency, osmoregulatory capacity (OC) and selected metabolic and haematological variables in Litopenaeus vannamei acclimated to low‐salinity water (3 g L−1) were evaluated. Supplemented astaxanthin at 80 mg kg−1 improved growth, survival and moult frequency in shrimp. The lowest OC was also exhibited in shrimp fed with dietary astaxanthin at 80 mg kg−1. Shrimp haemolymph concentrations of glucose, lactate, haemocyanin and total haemocyte count were all significantly enhanced by feeding the diet supplemented with 80 mg astaxanthin kg−1 compared with shrimp fed with the other diets. On the basis of these results, dietary astaxanthin supplementation of 80 mg kg−1 is recommended for juvenile L. vannamei cultured in low‐salinity water.  相似文献   

13.
Channel catfish Ictalurus punctatus were vaccinated at 12 d of age (post‐hatch) by a 2‐min bath immersion with attenuated Edwardsiella ictaluri RE‐33 at doses of 2.5 × 105, 2.5 × 106, and 2.4 × 107 colony‐forming units CFU/mL of water. Following vaccination, RE‐33 was recovered from a greater percentage of fry that were vaccinated at the high and intermediate doses compared to fry vaccinated at the lowest dose. Independent of dose, the greatest percentage of RE‐33 positive fry occurred between 1 and 6 d post‐vaccination with a significant decrease in positive fry observed on day 12. A significant increase in mortality occurred 6 to 12 d post‐vaccination in fry vaccinated at the highest dose. No differences in post‐vaccination mortalities occurred between the other treatments. Following virulent E. ictaluri challenge, mortalities of fish vaccinated at doses of 2.5 × 106 and 2.4 × 107 CFU/mL were significantly less than those of fish vaccinated at 2.5 × 105 CFU/mL and sham‐vaccinated control fish. These data show that vaccination with RE‐33 can offer protection against subsequent virulent E. ictaluri infection.  相似文献   

14.
This study examined the diversity of siderophore‐producing bacteria in the intestinal tracts of coastal fish in Japan and screened candidate bacterial strains for probiotic use in aquaculture. Of the 2637 bacteria isolated from the 27 fish specimens (13 species) and six environmental samples collected in this study, 266 isolates exhibited the ability to produce siderophores. Siderophore producers were detected in the intestines of 18 of the fish specimens caught (68%) at densities of 2.3 × 104–2.3 × 108 CFU g?1, in all three seawater samples at 2.0 × 102–1.3 × 103 CFU mL?1 and in all three sand samples at 2.6 × 101–2.8 × 104 CFU g?1. These findings suggest that siderophore‐producing bacteria are widely distributed in the intestinal tracts of coastal fish and their environments. Analysis of 16S rRNA gene sequences revealed that the siderophore producers belonged to 38 species, of which Vibrio splendidus, Vibrio ichthyoenteri and Vibrio crassostreae accounted for 32.7%, 19.5% and 11.3% of the 266 isolates, respectively, suggesting that these bacteria are indigenous to the intestinal tract of coastal fish. Six bacterial species, Enterovibri norvegicus, Photobacterium leiognathi, Photobacterium phosphoreum, Photobacterium rosenbergii, V. crassostrea and Vibrio scophthalmi were identified as possible candidates for use as probionts in fish aquaculture.  相似文献   

15.
This study aimed to find out whether dietary carotenoid (CD) supplement could influence the resistance of characins (Hyphessobrycon eques Steindachner) to ammonia stress. Two types of CD and its combination [astaxanthin (AX), β‐carotene (BC), 1 : 1 combination of AX and BC (MX)] at three concentrations (10, 20 and 40 mg kg−1) were used resulting in nine pigmented diets. No differences in growth and survival of the fish among treatments were found after 8‐week rearing. Experimental and control fish were then exposed to 15 mg total ammonia nitrogen L−1 (stress group) and 0.15 mg total ammonia nitrogen L−1 (normal group) for 72 h, and their blood was withdrawn. No mortality resulted under such TAN concentrations. Serum total antioxidant status (TAS), serum antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidases (GPx)] and serum transaminases [alanine aminotransferase (ALT), aspartate aminotransferase (AST)] were chosen as indices of fish antioxidant capacity or stress resistance. SOD, GPx and AST were affected by the interactions of dietary CD and ammonia stress. The activities of TAS, SOD, GPx and AST increased under the stress. Dietary CD reduced serum SOD, GPx, ALT and AST activities. In conclusion, dietary CD increased the resistance of characins to ammonia stress.  相似文献   

16.
A feeding trial was conducted to investigate the effect of different levels of Bacillus subtilis LT3‐1 in diets on growth, immune parameters, intestinal morphology and disease resistance in genetically improved farmed tilapia, Oreochromis niloticus. Fish (46.91 ± 0.17 g) were fed with a basal diet supplemented with B. subtilis LT3‐1 at 0 (B0), 3.8 × 1010 (B1), 7.6 × 1010 (B2), 1.14 × 1011 (B3) and 1.52 × 1011 (B4) CFU kg?1 for 6 weeks. The results showed that the weight gain of fish in B1 group was significantly enhanced compared to that in B0 group (p < 0.05). The addition of B. subtilis significantly affected serum biochemical indices (total protein, albumin, aspartate aminotransferase, alkaline phosphatase). Besides, the haematocrit, total counts of red and white blood cells, as well as the serum catalase and lysozyme activities, were increased, whereas the serum malondialdehyde, the serum immunoglobulin M and complement three contents were reduced. Parameters for intestinal morphology suggested a healthier intestine for the fish fed B. subtilis‐supplemented diets than fish fed the control diet. The survival rate after Streptococcus agalactiae challenge increased in tilapia fed with B. subtilis. The present study demonstrated B. subtilis can effectively improve growth, immunological status and resistance against S. agalactiae infection in tilapia farming.  相似文献   

17.
The present study aimed to investigate the effects of dietary supplementation of Lactobacillus delbrueckii (L. delbrueckii) on growth performance, body composition, intestinal enzyme activities and gene expression of Cyprinus carpio Huanghe var. Fish (mean 1.05 ± 0.03 g in triplicate) were conducted for 8 weeks with five treatments in triplicate. The fish in the control were fed a basal diet, and those in D2, D3, D4 and D5 were fed basal diet containing L. delbrueckii at 1 × 10 CFU/g, 1 × 10 CFU/g, 1 × 10 CFU/g and 1 × 10 CFU/g. The growth performance and the hepatic IGF‐I expression of fish increased significantly as L. delbrueckii level increased from 0 to 1 × 10 CFU/g, but decreased significantly with further increasing L. delbrueckii levels. The whole body protein, lipid contents, intestinal digestive and absorptive enzyme activities were significantly affected by dietary L. delbrueckii levels with the highest values observed in fish fed diet containing 1 × 106 CFU/g L. delbrueckii. The carbohydrate content showed the opposite trend. The results suggest that supplementation of L. delbrueckii as probiotic in the diet at approximately 1 × 10 CFU/g can improve growth performance, intestinal enzyme activities and the growth‐related gene expression in Cyprinus carpio Huanghe var.  相似文献   

18.
An 8‐week feeding trial was conducted to evaluate the efficacy of dietary l ‐ascorbic acid (AA) dosages on immunity, growth and survival of the fingerlings of Labeo rohita. AA was supplemented at 0, 100, 200 and 500 mg kg−1 basal diets. Each diet was fed for 8 weeks to duplicate groups of fingerlings of rohu with initial body weight of 35 ± 5 g. Selected biochemical and haematological analyses were evaluated every second week. At the end of the feeding trial of 56 days, fish were divided into two subgroups under each major treatment group for challenge with two pathogens, Aeromonas hydrophila and Edwardsiella tarda. The mortality (%) and agglutinating antibody titre were recorded on 28th day postchallenge. Non‐specific immune parameters like superoxide anion production, lysozyme activity and complement activity increased independently of the levels of AA in the diet. Whereas phagocytic ratio, phagocytic indices, lymphokine production indices and serum bactericidal activity were better in the group of fish fed with 200 mg AA kg−1 feed for 42 days. However, growth parameters such as specific growth rate, feed conversion ratio and survival were better in the group of fish fed with the highest level of AA through feed for 56 days. These data indicated that elevated levels of dietary AA could be recommended for optimum immunity, growth and survival of fingerlings of L. rohita.  相似文献   

19.
Low and unstable shrimp yields of the improved extensive shrimp system has been a tremendous obstacle for economic development in the coastal areas of Southern Vietnam. To investigate the biological characteristics of this system, ponds in the coastal Cai Nuoc district, Mekong delta of Vietnam, were monitored. Results showed that the system was not optimal for shrimp. While chlorophyll a (chl a) (1.51–37.2 μg L?1), phytoplankton density (6333–974 444 cells L?1) and zooplankton density (7.1–517.2 ind L?1) were abundant and comparable to shrimp farms elsewhere, zoobenthic community was very poor (7–1971 ind m?2). Toxin‐producing cyanobacteria (Oscillatoria limosa, Oscillatoria formosa, Anabaena sp. and Phormidium tenue) were found. Total bacteria and Vibrios were present in large numbers (respectively 1.04 × 105 and 6.64 × 102 CFU mL?1 in pond water, 6.33 × 105 and 9.47 × 103 CFU g?1 in sediment). Presence of toxin‐producing organisms, poor zoobenthic community and abundance of Vibrios all can enhance shrimp susceptibility to diseases. The following measures are recommended to improve the situation: (1) complete testing of seeds for pathogens, (2) not to incorporate fish into shrimp ponds and (3) applying no‐culture breaks and pathogen‐killing chemicals.  相似文献   

20.
Four isonitrogenous [30% crude protein (CP)] diets containing different gross energy levels (13.39, 16.74, 20.50 and 23.85 kJ g−1) were evaluated to determine the optimum energy for the Malawian tilapia Oreochromis shiranus. Each tank (120 L) was stocked with 18 juvenile tilapia (average weight 7.32±0.25 g) and they were fed the experimental diets for 10 weeks. The final average weight of the fish was approximately twofold higher (range: 12.64–16.77 g) than the initial weight. The dietary energy significantly (P<0.05) influenced growth. The average weight of fish fed dietary energy level 20.50 kJ g−1 was significantly higher (P<0.05) than the weight of the fish fed any of the other experimental diets. There was no significant difference in growth of fish fed 13.39 and 16.74 kJ g−1 energy levels, but 23.85 kJ g−1 produced the lowest growth rates. There were no significant differences (P>0.05) between feed intake across the treatments. Feed conversion ratio (range: 2.2–3.0) and protein efficiency ratio (range: 1.10–1.50) among the dietary treatment groups were in agreement with trends for weight gain. Dietary energy level significantly (P<0.05) influenced the body composition of O. shiranus. Whole‐body moisture (range: 64.27–67.15%) and ash (range: 13.21–14.73%) decreased in all treatments. Whole‐body protein (range: 63.57–66.16%) increased only in groups fed on the diet containing 20.50 kJ g−1. Whole‐body fat (range: 13.58–17.27%) and gross energy (range: 28.411–33.210 kJ g−1) increased significantly (P<0.05). Fish survival was 100% in all treatments. The results demonstrated that to maximize growth at a temperature of 23°C, O. shiranus should be fed diets containing 20.50 kJ g−1 gross energy.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号