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1.
Francisella noatunensis orientalis is a bacterium that causes emerging bacteriosis in Nile tilapia (Oreochromis niloticus) in many parts of the world, including Brazil. It is a non-motile, Gram-negative, strictly aerobic, facultative intracellular coccobacillus. This species of bacteria is responsible for low to high mortality in fish farms, causing economic losses for fish farmers. This study aimed to detect the presence of F. noatunensis orientalis using qPCR (real-time polymerase chain reaction) and to describe lesions caused by the bacterium in O. niloticus in Brazilian aquaculture. For this purpose, 360 fish from six fish farms (30 per farm) were sampled at two time points (n = 180 per sampling). Necropsies and histopathology were performed for lesion observation, in addition to qPCR and sequencing for detection and identification of Francisella species. Environmental data were collected using a multiparameter sonde YSI EXO2. All measured limnological variables were within the optimum range for cultivation of Nile tilapia. The major lesions present were melanization of the skin, splenomegaly, granulomas, and inflammatory cell responses. The prevalence of francisellosis varied from 0 to 86.66% between time periods and fish farms analyzed, and an outbreak was observed during the second sampling period. This study describes the prevalence of francisellosis in O. niloticus and reports that the lesions found are not exclusively associated with this bacterial disease.  相似文献   

2.
Partial substitutions of fish meal by 5, 15, or 25 % of Gracilaria cornea or Ulva rigida in experimental diets were evaluated to study their effects on biodiversity of intestinal microbiota composition in gilthead seabream (Sparus aurata) juveniles. The diets were offered to duplicate groups of 15 juvenile fish (14.0 ± 0.5 g) for 70 days, and at the end of the experiment the intestinal microbiota from four specimens of each treatment was analysed by denaturing gel gradient electrophoresis. Results showed that the substitution of fish meal by algae meal induced important modifications in the intestinal microbiota community, as a big reduction of the biodiversity when the highest percentage (25 %) of U. rigida was included. On the contrary, an increase on the number of species was detected when a 15 % of algae was included. Various Lactobacillus delbrueckii subspecies were selectively stimulated when G. cornea was included in the feed, and other bacterial species, such as those included in the Vibrio genus, were reduced.  相似文献   

3.
Several outbreaks of Streptococcus agalactiae infection of bighead carp (Aristichthys nobilis) were observed in China. The molecular epidemiology and pathogenicity of S. agalactiae in bighead carp and tilapia (Oreochromis sp.) is poorly understood. In the present study, we identified S. agalactiae strains isolated from diseased bighead carp using the API 20 Strep kit and 16S rDNA sequencing and determined whether these strains came from tilapia. Of the 46 identified S. agalactiae strains, 24 strains were successfully isolated from diseased bighead carps, 20 S. agalactiae strains were isolated from tilapia, and two S. agalactiae strains were isolated from tiger frog (Hoplobatrachus chinensis). The results of molecular typing, including multilocus sequence typing, molecular serotyping, surface protein gene detection, and virulence-related gene detection showed that the 44 strains from bighead carp and tilapia were highly similar, whereas different from tiger frog GBS strains. Remarkably, the bighead carp strain Hn1404 showed high virulence in bighead carp and zebrafish. Moreover, this strain was pathogenic to Nile tilapia (Oreochromis niloticus). In addition, comparative genomic analysis showed that isolate Hn1404 had a close relationship with the bighead carp and tilapia S. agalactiae strains. All the analyses of the genetic characteristics of bighead carp and tilapia strains showed that tilapia S. agalactiae strains could be transmitted to other fish species such as bighead carp.  相似文献   

4.
The yeast Saccharomyces cerevisiae is one of the commonest probiotics incorporated in aquafeeds. An 84-day feeding trial was conducted to evaluate the effects of varying dietary inclusions of S. cerevisiae, 0% (control), 3% (YF3), 5% (YF5), and 7% (YF7), on growth, stress tolerance, and disease resistance in juvenile (body mass ~?21 g) Nile tilapia (Oreochromis niloticus). Fish were randomly distributed in groups of 20 into 12 1-m3 hapas and fed isoenergetic (~?17 kJ g?1 gross energy) and isonitrogenous (~?300 g kg?1 crude protein) diets at 3% of their bulk weight daily. Specific growth rates were significantly higher for the yeast-fed fish (0.77–0.78% day?1) than for the control fish (0.60% day?1) and resulted in significantly higher mean final weights for the yeast-treated groups. Protein and lipid retention efficiencies were also significantly higher in the yeast-fed fish than in the control group. In subsequent stress challenge trials, the yeast-fed fish had greater tolerance to acute heat as well as hypoxia exposure than the control fish. Survival rates of the yeast-treated groups following sudden exposure to elevated water temperature (40 °C) ranged from 82.5 to 100% compared to 15% for the control. Mean survival rates following a 24-h hypoxia exposure were also generally significantly higher for the yeast-fed fish. The probiotic groups recorded a relative percent survival (RPS) of 75% after a 14-day Aeromonas hydrophila infection challenge. The results of this study indicate that S. cerevisiae as an additive in Nile tilapia diets has beneficial impacts on growth, stress tolerance, and disease resistance.  相似文献   

5.
A feeding experiment was conducted to investigate the effects of exogenous non-starch polysaccharide (NSP)-degrading enzymes in diets containing Gracilaria lemaneiformis (GL) on growth performance and digestive enzyme activities of white-spotted snapper Lutjanus stellatus Akazaki (initial mass 8.0 ± 0.1 g). A basal diet (D0) containing a mixed protein source (fish meal, soybean meal and GL meal) was used as the control. Two diets supplemented with 0.5 g (D1) and 1 g (D2) exogenous NSP-degrading enzymes per kilogram of diet were formulated. Each diet was assigned to triplicate groups of fish in a total of nine floating sea cages (270 fish, 30 fish per cage). After a 60-day feeding trail, significantly higher weight gain, specific growth ratio and feed efficiency ratio were observed in fish fed D2 diet compared to those of control (P < 0.05). Body lipid, moisture and ash contents were not significantly affected by NSP-degrading enzyme supplementation, but significantly higher protein content was noticed in fish fed D2 diet compared to that of control (P < 0.05). The amylase activity in the stomach and intestine was significantly higher in fish fed D2 diet (P < 0.05), but no significant differences were observed in pepsin and lipase activities in the stomach or trypsin and lipase activities in the intestine between all treatments. The results suggested that addition of 1 g kg?1 NSP-degrading enzymes in diet could efficiently improve seaweed feed utilization and growth performance of white-spotted snapper fish.  相似文献   

6.
This study examined the effects of two probiotics (Virgibacillus proomii and Bacillus mojavensis) on the digestive enzyme activity, survival and growth of Dicentrarchus labrax at various ontogenetic stages in three separate experiments. These probiotics were incorporated as single or mixed into fish feed for a period of 60 days. The growth parameters, proximate composition of whole body, digestive enzymes and gut microbiology were monitored at regular. The increments in length and weight and the survival were significantly higher (P < 0.05), and the values of food conversions were significantly lower (P < 0.05) in fishes fed the probiotic. The administration of V. proomii and B. mojavensis in diet resulted in an increase (P > 0.05) in body ash and protein content and in the specific activity of phosphatase alkaline and amylase in the digestive tract of all the fishes. V. proomii and B. mojavensis persisted in the fish intestine and in the feed in high numbers during the feeding period (group 1: 5.8 × 104 CFU/ml, group 2: 9.6 × 104 CFU/ml, and group 3: 9.8 × 104 CFU/ml day 60). The two probiotics V. proomii and B. mojavensis were adequate for improved growth performance and survival and for healthy gut microenvironment of the host.  相似文献   

7.
This study was designed to assess the potential effects of Astragalus membranaceus (AM) on the growth performance and antioxidative stress response in bluegill sunfish (Lepomis macrochirus) exposed to challenging cold water temperature conditions. In this regard, fish with an average weight of 43 ± 1 g were divided into four groups and fed daily with an AM-free diet (control), and 1.5, 3, and 4.5 % (w/w) AM-incorporated diets for an 8-week period. Oxidative stress response, biochemical, and growth parameters were measured, and subgroups of fish were exposed to the outside challenging cold pond water temperature (1.6–9.9 °C) with an average of 7.0 ± 0.1 °C beyond the optimal temperature. The results showed that incorporating AM in the diet significantly improved growth performance parameters (body mass gain, specific growth rate, length, condition factor, and feed conversion ratio) and biochemicals (aspartate aminotransferase and alanine transaminase activities, and glucose and cortisol concentrations). In addition, markedly up-regulated superoxide dismutase, glutathione peroxidase, and catalase activities were observed in AM-treated fish groups over the control. Conclusively, feeding AM diets significantly increased (P < 0.05) growth performance and antioxidative stress profiles throughout the entire experiment, and this increase was much more pronounced at 8 weeks after the water temperature began to rise, which can be related to the nature of Bluegill fish as it is known to be a warm water fish. These findings are considered to be of great importance for sustainable aquaculture.  相似文献   

8.
The current study aimed to evaluate the possible effect of Origanum essential oil on innate immune parameters as well as the hematological profiles of Tilapia zillii following challenge with Vibrio anguillarum. Fifty-four of Tilapia zillii weighing 180?±?10.2 g were randomly distributed into three identical closed recirculating seawater systems. The study included three groups (G1, G2, and G3) repeated in triplicates. Fish of the first two groups were fed on a basal diet without herbs, whereas fish of the last group were fed on a basal diet supplemented with Origanum essential oil at concentration 1 g kg?1 for 15 days. Subsequently, fish of G2 and G3 subjected to a peritoneal inflammation by intraperitoneally injecting V. anguillarum (5.5?×?105 CFU mL?1), whereas fish of G1 injected with saline and served as control. Fish of all groups were then sampled at 4, 12, and 24 h post injection. No mortalities were observed in both basal and Origanum fed groups. However, some specimens of fish fed basal diet showed dorsal fin erosions, eroded mouth, and detached skin. Although the kinetics of RBCs, WBCs, Hb, and differential leukocyte values remained unchanged in fish fed different diets at the beginning of the trial, significant increases in those values were observed in fish fed Origanum essential oil at 12 and 24 h post injection. Similarly, an augmentation of plasma proteases, antiproteases, and lysozyme activities were recorded in fish fed Origanum essential oil at the same particular sampling points. A significant enhancement in plasma bactericidal capacity was only recorded in fish fed Origanum essential oil at 12 and 24 h post challenge compared to those fed basal diet. In conclusion, Origanum essential oil had a pronounced influence on the innate immunity and increased the fish resistance to V. anguillarum. These data gave insight into the potential use of Origanum in prophylactic strategies against threatening pathogens.  相似文献   

9.
Increasing demand for eco-friendly botanical piscicides and pesticides as replacements for harmful synthetic chemicals has led to investigation of new sources of plant materials. Stem bark of Terminalia arjuna, which has been used as a popular folk medicine since ancient time, was examined for its piscicidal activity. This study aims to determine toxicity of ethanol extract of T. arjuna bark on fresh water stinging catfish (Heteropneustes fossilis), along with evaluation of changes in hematological parameters of the fishes exposed to a lethal concentration. The percent mortality of fishes varied significantly in response to concentrations of the extract and exposure times (between exposure time F = 36.57, p < 0.001; between concentrations F = 39.93, p < 0.001). The lethal concentrations (LC50) of ethanol extract were found to be 12.7, 8.94, 5.63 and 4.71 mg/l for 24, 48, 72 and 96 h, respectively. During acute toxicity test, blood samples of treatment fishes showed significant decreases in the red blood cells count, hematocrit content, hemoglobin concentration, mean corpuscular hemoglobin concentration and plasma protein level when compared to those of the control group, while there were significant increases in the mean corpuscular volume, mean corpuscular hemoglobin, white blood cells count and plasma glucose concentration. These results suggest that T. arjuna bark extract could be considered as a potent piscicide due to its toxic effect on fish, particularly fish hematology.  相似文献   

10.
We evaluated the effects of diets incorporating the red algae Pyropia yezoensis, prepared by several different extraction methods, on the growth of juvenile Japanese flounder Paralichthys olivaceus. We assessed growth performance, as well as the levels of amino acids, fatty acids, insulin-like growth factor I (IGF-I) and interleukins (ILs). Four experimental diets were developed based on different methods of processing P. yezoensis. A commercial feed, laver powder (P), high-pressure heat extraction of laver (HPHE) and acid hydrolysis extraction of laver were used as the experimental diets. Three experimental replicates were established for each diet (40 fish/group, body weight 123.7 ± 1.1 g), and the fish were fed for 6 weeks. We found no significant differences in weight gain, specific growth rate or feeding efficiency among the groups (P > 0.05); however, the fish fed HPHE had the greatest growth performance. Fish fed the laver extracts exhibited the highest protein efficiency ratio compared with the control and P groups. The experimental groups fed P. yezoensis extracts had significantly higher levels of IGF-I (P < 0.05) than those of the control group. High levels of IL-2 were found in the P and HPHE groups, IL-12 in the HPHE group, and IL-6 in all experimental groups. Therefore, these results suggest that a P. yezoensis extract improved the growth performance and immunity of Japanese flounder. In particular, the high-pressure heating process was a useful extraction method for preparing a P. yezoensis extract, which had beneficial effects as a dietary supplement in Japanese flounder.  相似文献   

11.
Fucoidan mainly produced by brown algae is a sulfated polysaccharide with fucose as a main molecule backbone. The objective of this research was to evaluate the non-specific immune potentiating activity of fucoidan from a tropical brown alga, Sargassum cristaefolium indigenous to the Gunungkidul coast, Yogyakarta, Indonesia. Fucoidan was extracted by acidic extraction, separated from alginate by CaCl2 precipitation and precipitated with ethanol. To know the component of fucoidan, acid hydrolysis was conducted and analyzed by using silica gel thin layer chromatography. In these analyses, a commercial fucoidan from Fucus vesiculosus was used as a standard fucoidan. Fucoidan isolated from S. cristaefolium was composed by monosaccharide components of fucose and galactose. The result revealed that injection of fucoidan increased phagocytic activity, total plasma protein, leukocrit and leukocyte count significantly (p < 0.05). The immunomodulating activity of fucoidan from S. cristaefolium was comparable to that of fucoidan standard from F. vesiculosus. However, administration of fucoidan did not affect the phagocytic index and leukocyte differentiation. Injection of fucoidan from S. cristaefolium effectively increased innate immunity parameters of tilapia at doses of 0.4–0.6 mg/kg fish suggested that this fucoidan was potential use for immunostimulant to control fish diseases.  相似文献   

12.
Hospital effluents contain myriad of mutagens and genotoxins capable of increasing DNA damage in aquatic biota. African mudfish, Clarias gariepinus, are exposed to genotoxins when cultured in swamps and derelict water bodies often contaminated by effluents. Moreover, its DNA is susceptible to xenobiotic-induced lesions since it lacks l-gulonolactone oxidase and hence cannot synthesize l-ascorbic acid. This study investigated 96-h acute toxicity and protective effects of dietary ascorbic acid (AA) against micronucleus (MN) and abnormal nuclear (NAs) formation in C. gariepinus exposed to sub-lethal concentrations of hospital effluent. Six concentrations (0.5–3.0%) of the effluent were selected to determine the 96-h acute toxicity of the effluent in C. gariepinus, after range finding test. Fish were exposed to sub-lethal concentrations (0.08–1.30%) of the 96 h LC50. Two other groups were exposed to the 96 h LC50 (1.30%) of the effluent +50 and +100 mg/kg of dietary ascorbic for 7 days, and MN and NAs assessed in peripheral erythrocytes. The 96 h LC50 (1.30%) was 1.18 times more toxic than the 24 h LC50 (1.54%), indicating that the toxicity of the effluent increased with exposure duration. MN, nuclear bud, enucleated, fragmented nucleus (apoptosis), and necrotic erythrocytes significantly increase in effluent treated fish. Dietary AA reduced MN from 6.35-fold (1.30% treated group) to 3.72-fold (1.30% + 50 mg AA) and 3.54-fold (1.30% + 100 mg AA). Also, AA reduced total NAs from 2.26-fold (1.30%) to 1.40-fold (1.30% + 50 mg AA) and 1.06-fold (1.30% + 100 mg AA) compared to the control. Heavy metals and physicochemical parameters analyzed in the tested effluent possibly induced the mortality and cytogenotoxicity in C. gariepinus, and this was ameliorated by dietary AA.  相似文献   

13.
Multidomain proapoptotic Bcl-2-associated X (Bax) protein is an essential effector responsible for mitochondrial outer membrane permeabilization, resulting in cell death via apoptosis. In this study, two Bax genes of grass carp (Ctenopharyngodon idellus), designated as CiBax1 and CiBax2, were isolated and analyzed. The obtained CiBax1 cDNA is 2058 bp long, with a 579 bp open reading frame (ORF) coding a protein of 192 amino acid residues. The full-length cDNA of CiBax2 is 1161 bp, with a 618 bp ORF coding 205 amino acids. Both CiBax1 and CiBax2 are typical members of Bcl-2 family containing conserved Bcl and C-terminal domains, and they share conserved synteny with zebrafish Bax genes despite the grass carp Bax mapping to different linkage groups. Phylogenetic analysis showed that CiBax1 was clustered with Bax from most teleost fish, and CiBax2 was close to Bax2 from teleost fish but far separated from that of Salmo salar. Quantitative real-time PCR analysis revealed broad expression of CiBax1 and CiBax2 in tissues from healthy grass carp, but the relative expression level differed. The mRNA expression of CiBax1 and CiBax2 was both upregulated significantly and peaked in all examined tissues at days 5 or 6 post-infection with grass carp reovirus. Subcellular localization indicated that CiBax1 protein was localized in both nucleus and cytosol, while CiBax2 protein only in cytosol. Moreover, CiBax2, but not CiBax1 was colocalized with mitochondrion under normal condition. Taken together, the findings would be helpful for further understanding of the function of Bax in teleost fish.  相似文献   

14.
We investigated the effects of replacing non-fermented wheat grains with wheat grains fermented by fungal mycelia in the diet of juvenile rainbow trout (Oncorhynchus mykiss). We assessed growth performance, feeding parameters, and body composition in three experimental groups (0.33?±?0.01 g, in triplicates of 50 individuals each). The diets for all the groups contained ca. 43% protein and 19% lipids. Experimental diets were made by replacing the 100 g kg?1 of wheat grains present in the basal diet (CTRL) with the same proportion of wheat grains fermented by Pleurotus ostreatus (PWD) or Lentinus edodes (LWD) mycelium. Fish were fed to apparent satiation twice a day for 56 days. Both, PWD and LWD, significantly increased fish body weight from day 28 onwards. Final body weight was 2.37?±?0.04 g (CTRL), 4.29?±?0.02 g (PWD), and 3.50?±?0.05 g (LWD), and feeding efficiency (%) was increased from 64.5?±?0.7 (CTRL) to 92.5?±?0.5 (PWD) and 84.8?±?1.5 (LWD). The experimental diets also improved nutrient retention efficiency (%): 30.0?±?0.5 (PWD), 27.7?±?1.1 (LWD), and 21.0?±?0.1 (CTRL), for crude protein; 40.3?±?0.6 (PWD), 31.0?±?1.8 (LWD), and 16.1?±?0.7 (CTRL), for ether extract; and 16.1?±?0.1 (PWD), 14.0?±?0.3 (LWD), and 11.6?±?0.6 (CTRL), for phosphorus. Body lipid content was highest for PWD followed by LWD and CTRL (81.4?±?1.4, 63.2?±?2.5, 42.3?±?2.6 g kg?1, respectively), while viscerosomatic index was lowest for PWD (p?<?0.05). Liver glycogen in LWD and PWD fish (0.62?±?0.10 and 0.21?±?0.08% liver weight) was significantly higher than in CTRL fish (0.05?±?0.01% liver weight). Wheat-mycelium meals appear to be suitable dietary ingredients for improving juvenile rainbow trout growth and nutritional performance. These benefits vary according to the mushroom species used.  相似文献   

15.
Corn gluten meal (CGM) has a high protein content and absence of antinutrients. However, it has high levels of carotenoids that can cause a yellowing of fish fillets and impair further commercialisation. Graded levels of CGM were incorporated in pacu diets to replace soybean meal (SM) protein. The experimental diets were formulated to be isonitrogenous (220 g kg?1 digestible protein) and isoenergetic (13.4 MJ kg?1 digestible energy) with 0, 25, 50, 75, and 100 % replacement of SM protein by CGM protein over a 60-day period. One hundred fish (32.79 ± 3.43 g) were randomly distributed in 20 experimental cages (70 L) placed within five (1000 L) aquaria with continuous water renewal. The experimental design was completely randomised with five treatments and four replicates. A quadratic effect (P < 0.05) was observed for fillet and carcass yields, feed conversion ratio, weight gain, and specific growth rate, with the optimum values for replacement of SM protein by CGM protein estimated as 21.95, 29.13, 30.94, 37.71, and 38.75 %, respectively. There were no differences (P > 0.05) for blood parameters, proximal composition, water-holding capacity, pH, lipid oxidation, and a* value of fillets. The L* and b* values of fillets showed differences (P < 0.05). Replacement between 21.95 and 38.75 % of SM protein by CGM protein (5.37 and 9.48 % of inclusion in the diet) improves the growth performance and body yield of pacu juveniles without altering blood parameters or affecting the fillet quality.  相似文献   

16.
Seeking alternatives to the depleting fish oil are crucial for marine fish aquaculture, which is currently dependent on fish oil as the primary source of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs). Five isonitrogenous (46% crude protein) and isolipidic (16% crude lipid) feed diets (FO, ISO2.9, ISO4.8, ISO6.7, ISO8.6) were formulated by partially replacing fish oil with microalgae Isochrysis galbana. These diets were fed to triplicate tanks of Trachinotus ovatus (mean initial weight 1.92 g) for 80 days. This work demonstrates that a moderate inclusion (around 4.5–5.0 wt%, equivalent to the replacement of 24–26 wt% fish oil) of I. galbana biomass in fish diet improves fish growth performance, lipid deposition and enhances total n-3 fatty acids, DHA, and EPA contents in neutral and polar lipids (PLs) of fish muscle and liver of T. ovatus. The results disclosed in this study suggest that I. galbana microalgae represents a potential high-quality substitute for fish-based ingredients in aquaculture feeds, which can be a promising sustainable solution to resolve the depleting fish oil resource in a cost-effective manner.  相似文献   

17.
Reproduction allows organisms to produce offspring. Animals shift from immature juveniles into mature adults and become capable of sexual reproduction during puberty, which culminates in the first spermiation and sperm hydration or ovulation. Reproduction is closely related to the precise control of the hypothalamic–pituitary–gonadal (HPG) axis. Kisspeptin peptides are considered as the important regulator of HPG axis in mammalian. However, the current understanding of kisspeptin in flatfish is not comprehensive. In this study, we cloned and analyzed the kiss2 and kissr2 genes in Cynoglossus semilaevis. Interesting alternative splicing in the 5′-untranslated regions (UTR) of the Cskissr2 gene was found. The expression profiles of Cskiss2 and Cskissr2 showed relative high messenger RNA (mRNA) levels at the late gastrula stage during embryonic development, at total length = 40 mm during early gonadal differentiation, and in the brains and gonads of all investigated tissues. These results suggested that the kisspeptin system participated in embryogenesis and in the regulation of gonadal differentiation and development. Considering that the control and regulatory mechanisms of kisspeptin in the central reproductive axis are still unclear, we documented that the intramuscular injection of kisspeptin caused different sGnRH and cGnRH mRNA levels in a dose- and tissue-dependent manner. The mRNA expressions of FSH and LH were stimulated in the ovary and were inhibited in the testis under the kisspeptin treatments. These results provided foundations for understanding the roles of kisspeptin in the neuroendocrine system in fish. The manipulation of the kisspeptin system may provide new opportunities to control the gonadal development and even reproduction in fish.  相似文献   

18.
The effects of transporting silver catfish (Rhamdia quelen) for 6 h in plastic bags containing 0 (control), 30 or 40 µL/L of essential oil (EO) from Lippia alba leaves were investigated. Prior to transport, the fish in the two experimental groups were sedated with 200 µL/L of EO for 3 min. After transport, dissolved oxygen, carbon dioxide, alkalinity, water hardness, pH, temperature and un-ionized ammonia levels in the transport water did not differ significantly among the groups. However, total ammonia nitrogen levels and net Na+, Cl? and K+ effluxes were significantly lower in the groups transported with EO of L. alba than those in the control group. PvO2, PvCO2 and HCO3 ? were higher after transporting fish in 40 µL/L of EO of L. alba, but there were no significant differences between groups regarding blood pH or hematocrit. Cortisol levels were significantly higher in fish transported in 30 µL/L of EO of L. alba compared to those of the control group. The metabolic parameters (glycogen, lactate, total amino acid, total ammonia and total protein) showed different responses after adding EO to the transport water. In conclusion, while the EO of L. alba is recommended for fish transport in the conditions tested in the present study because it was effective in reducing waterborne total ammonia levels and net ion loss, the higher hepatic oxidative stress in this species with the same EO concentrations reported by a previous study led us to conclude that the 10–20 µL/L concentration range of EO and lack of pre-sedation before transport are more effective.  相似文献   

19.
The present study was conducted to investigate the effects of stocking density on serum cortisol (COR) levels and expression of immune genes in the head kidney of juvenile GIFT tilapia (Oreochromis niloticus) after Streptococcus iniae (S. iniae) infection. Juveniles (2700) were distributed into 30 tanks at five stocking densities (150, 300, 450, 600 and 750 g/m3), and each treatment had six replicates. After a 45-day feeding trial, a S. iniae challenge study was conducted for 96 h. Differences in mortality, serum COR and gene expression of C-type lysozyme, heat-shock protein 70 (HSP70), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were analyzed. The levels of serum COR at all infected treatments were significantly higher compared with the levels of pre-infection (P < 0.05). At 96 h post-infection, serum COR levels of high stocking densities (600 and 750 g/m3) were significantly higher than those of low-density groups (P < 0.05); the mRNA levels of C-type lysozyme, HSP70, IL-1β, TNF-α and IFN-γ were significantly lower in tilapia reared at 600 g/m3 group than in those reared at 300 g/m3 group (P < 0.05). Fish reared in high-density treatments (600 and 750 g/m3) exhibited significantly higher post-challenge mortality (43.3 and 40.0 %) at 96 h following S. iniae infection, and it was significantly higher than other groups (P < 0.05). The data suggest that when living in high stocking density, GIFT tilapia showed decrease in immune capability, together with increased serum COR and susceptibility to S. iniae.  相似文献   

20.
In the present study, cellulase, protease, lipase and amylase activities were performed to investigate the effects of Lactococcus lactis subsp. lactis CF4MRS bioencapsulation of Artemia franciscana. Our results show that cellulase activities (total cellulase—FPase activity, exoglucanase and endoglucanase—CMCase activity) were significantly higher (P < 0.05) in A. franciscana tissue homogenates compared to those in the control group after 8 h of L. lactic bioencapsulation. Notably, an exception case was found in β-D-glucosidase activity, whereby the cellulase activity was not significantly different (P > 0.05) compared to the control group. Administrations of L. lactis at cell concentration of 108 CFU mL?1 showed considerable improvement of other important enzymatic activities such as amylase, protease and lipase in A. franciscana. The amylase/protease ratio in probiotic-treated A. franciscana was recorded at 0.343, approximately two times higher than those without probiotic administration (0.184). In contrary, amylase/lipase ratio showed half of a reduction (0.330) in L. lactis-administrated A. franciscana compared to the control (0.614). Our study suggests that important digestive enzymes, e.g., cellulase, amylase, protease and lipase, can be enhanced through bioencapsulation of A. franciscana with L. lactis subsp. lactis, which could in turn lead to further stimulation of endogenous enzymes in the fish and shrimp larvae.  相似文献   

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