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1.
A 60-day feeding trial was conducted to study the effect of dietary microbial levan on growth performance and metabolic responses of Cyprinus carpio fry exposed to sublethal dose (1/10th LC50) of fipronil [(±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile]. Two hundred and twenty five fry were randomly distributed in five treatments in triplicates. Four purified diets were prepared with graded levels of microbial levan. Five different treatment groups were levan control L0P0 (basal feed + 0 % levan without exposure to pesticide); pesticide control L0P1 (basal feed + 0 % levan with exposure to pesticide); L0.25P1 (basal feed + 0.25 % levan with exposure to pesticide); L0.50P1 (basal feed + 0.50 % levan with exposure to pesticide); and L0.75P1 (basal feed + 0.75 % levan with exposure to pesticide). Weight gain% and specific growth rate were significantly higher (p < 0.05) in levan fed groups compared to their non-levan fed counterpart. Highest (p < 0.05) content of ascorbic acid in muscle, liver and brain tissues was observed with higher level of dietary levan. Glucose-6-phosphate dehydrogenase activity decreased with the increasing level of dietary levan in the liver and muscle. Aspartate aminotransferase activity exhibited a second order polynomial relationship with the dietary levan, both in liver (Y = ?1.001x 2 + 5.366x + 5.812, r 2 = 0.887) and muscle (Y = ?0.566x 2 + 2.833x + 6.506, r 2 = 0.858) while alanine aminotransferase activity showed third order polynomial relationship both in liver (Y = 1.195x 3 ? 12.30x 2 + 35.23x + 9.874, r 2 = 0.879) and muscle (Y = 0.527x 3 ? 8.429x 2 + 31.80x + 8.718, r 2 = 0.990). Highest (p < 0.05) superoxide dismutase activity in gill was observed in the group fed with 0.75 % levan supplemented diet. Overall results indicated that dietary microbial levan at 0.75 % in C. carpio fry ameliorated the negative effects of fipronil and augmented the growth.  相似文献   

2.
Effect of nitrite exposure on growth and immuno‐metabolic responses of Labeo rohita fed L‐tryptophan (TRP) was studied. Fish previously fed normal and elevated levels of tryptophan for 60 days were exposed to nitrite (2.0 mg L?1) for another 45 days with same feeding regime. There were four treatment groups, viz., TRP0‐N (control), TRP0+N, TRP0.75+N (0.75% supplemental tryptophan in the diet) and TRP1.5+N (1.5% supplemental tryptophan in the diet). Highest weight gain% and SGR were observed in control and lowest in TRP0+N. Dietary supplementation of elevated levels of tryptophan augmented weight gain% and SGR. Nitrite exposed groups recorded higher catalase, SOD, LDH, AST and ALT activities compared with control. However, activities reduced with additional levels of tryptophan supplementation. Nitrite exposure reduced WBC count, total protein, albumin, globulin and lysozyme activity compared with unexposed group but groups which were fed additional amounts of tryptophan restored total protein, albumin and globulin similar to TRP0‐N. In conclusion, nitrite exposure had adversely affected growth, increased activities of LDH, AST, ALT, catalase, but decreased WBC, serum protein, lysozyme and acetylcholine esterase activity of L. rohita. Normal requirement of tryptophan was unable to combat nitrite stress. However, dietary fortification with tryptophan (minimum 0.75% of diet + normal requirement) found effective in combating nitrite induced stress.  相似文献   

3.
The nitrite toxicity was estimated in juveniles of L. vannamei. The 24, 48, 72 and 96 h LC50 of nitrite‐N on juveniles were 8.1, 7.9, 6.8 and 5.7 mg L?1 at 0.6 g L?1; 14.4, 9.6 8.3 and 7.0 mg L?1 at 1.0 g L?1; 19.4, 15.4, 13.4 and 12.4 mg L?1 at 2.0 g L?1 of salinity respectively. The tolerance of juveniles to nitrite decreased at 96 h of exposure by 18.6% and 54.0%, when salinity declined from 1.0 to 0.6 g L?1 and from 2.0 to 0.6 g L?1 respectively. The safe concentrations at salinities of 0.6, 1.0 and 2.0 g L?1 were 0.28, 0.35 and 0.62 mg L?1 nitrite‐N respectively. The relationship between LC50 (mg L?1), salinity (S) (g L?1) and exposure time (T) (h) was LC50 = 8.4688 + 5.6764S – 0.0762T for salinities from 0.6 to 2.0 g L?1 and for exposure times from 24 to 96 h; the relationship between survival (%) and nitrite‐N concentration (C) for salinity of 0.6–2.0 g L?1, nitrite‐N concentrations of 0–40 mg L?1 and exposure times from 0 to 96 h was as follows: survival (%) = 0.8442 + 0.1909S – 0.0038T – 0.0277C + 0.0008ST + 0.0001CT–0.0029SC, and the tentative equation for predicting the 96‐h LC50 to salinities from 0.6 to 35 g L?1 in L. vannamei juveniles (3.9–4.4 g) was 96‐h LC50 = 0.2127 S2 + 1.558S + 5.9868. For nitrite toxicity, it is shown that a small change in salinity of waters from 2.0 to 0.6 g L?1 is more critical for L. vannamei than when wider differences in salinity occur in brackish and marine waters (15–35 g L?1).  相似文献   

4.
Indoxacarb is a relatively new pesticide from oxadiazin class, which is used near carp ponds for agricultural purposes. Thus, the aim of this study was to determine indoxacarb effects on common carp (Cyprinus carpio). The fish were exposed to 0 (control), 0.75, 1.5 and 3 ppm of indoxacarb over 21 days and plasma biochemical characteristics and liver histopathology were examined. Exposure to indoxacarb induced fall in total protein after 21 days. Globulin increased after 7 days and then decreased after 14‐ and 21‐day exposure. Plasma alanine transaminase and aspartate transaminase activities increased in 1.5 and 3 ppm treatments after 7‐day exposure. Indoxacarb exposure significantly decreased plasma alkaline phosphatase after 7 days with no change at the second and third samplings. After 7 days, plasma T3 levels had no significant change; however, it decreased after 14 days in the 1.5 and 3 ppm treatments and also reduced after 21‐day exposure to the 3 ppm treatment compared to the control group. Plasma T4 level only decreased significantly in the 3 ppm treatment compared to the control group after 21 days. Different histopathological symptoms such as necrosis, hyperaemia, sinusoidal space extension, pyknotic nuclei, leucocyte infiltration and melanomacrophage aggregates were observed after 21‐day exposure to indoxacarb. The symptoms intensity was dependent on indoxacarb concentration. In conclusion, the present results show that indoxacarb exposure adversely affects common carp health and welfare, which consequently may induce serious problems in this species aquaculture.  相似文献   

5.
This study explores the anaesthetic activity of Alpinia galanga oil (AGO) in fish. Cyprinus carpio (koi carp) was used as a fish model. It was found that the induction time to stage 3 anaesthesia and the recovery time of the fish after exposure to AGO were exponentially and polynomially correlated to AGO concentrations. The viability of normal blood cells of koi carp anaesthetized with 500 mg/L AGO was found to be higher than 90% for normal red blood cells and white blood cells and 89% for peripheral blood nuclear cells indicating nontoxicity of AGO to the fish. A concentration of 300 mg/L of AGO was the most suitable for anaesthetizing koi carp due to the safety and effectiveness aspects as being ideally fitted to anaesthetic criteria. This concentration gave the induction time of 205.55 ± 5.07 s and the recovery time of 202.50 ± 9.30 s. Determination of stress biomarker such as blood cortisol and glucose as well as gene expression showed that the blood cortisol level of the fish anaesthetized with AGO was similar to normal levels. Moreover, blood glucose level was significantly less increased than those anaesthetized with tricaine methanesulfonate. Gene expressions of the fish cortisol receptor, cytochrome oxidase subunit1, heat shock protein 70 and Na+/K+‐ATPaseα3 were significantly reduced after exposure to AGO indicating the advantages of AGO on fish stress reduction. Thus, AGO is a promising natural source for an alternative fish anaesthetics.  相似文献   

6.
A feeding trial was conducted to evaluate the effect of inclusion of Sesbania leaf meal in the diet of Cyprinus carpio as a replacer of de‐oiled rice bran (DORB). Bacillus subtilis was used to ferment the Sesbania leaf meal (SLM) to produce FSLM (fermented sesbania leaf meal). Fishes were fed with five isonitrogenous (30% CP) and isocaloric diets for 60 days and treatments were viz., C (30% DORB, 0% SLM), R15 (15% DORB, 15% SLM), R30 (0% DORB, 30% SLM), F15 (15% DORB, 15%FSLM) and F30 (0% DORB, 30% FSLM) by replacing DORB with SLM. A similar growth performance with control was observed in 15% FSLM group while there was a growth reduction in all the raw leaf meal fed groups. Similarly, the expression of insulin‐like growth factor‐1 (IGF‐1) was significantly (p < .05) higher in control and 15% FSLM fed groups. Growth and metabolic enzymes such as protease, amylase, ALT and AST activities were significantly higher in the fermented leaf meal fed groups compared to their non‐fermented counterparts. Antioxidant enzymes, serum transaminase enzymes (SGOT, SGPT) and total bilirubin (TBR) were found to be increased by enhanced level of RSLM, however, reduced by inclusion of FSLM. However, 30% inclusion level of FSLM even after fermentation showed detrimental effect on growth and metabolic response at cellular and molecular level. Thus, the results concluded that fermented Sesbania leaf meal (FSLM) using B. subtilis could replace 50% DORB (15% FSLM group) in the diet of C. carpio without affecting the growth and other physiological responses.  相似文献   

7.
Different laboratory synthesized metal nanoparticles viz. Copper oxide (CuO), Zinc oxide (ZnO) and silver doped titanium dioxide (Ag‐TiO2) were studied for their effect on hatching and survival of larvae and fry of Indian major carp, rohu, Labeo rohita both in direct application in tank water & coated onto tanks. Among these nanoparticles, CuO and ZnO nanoparticles exhibited highest percentage of hatching in both direct addition (78.0 ± 3.1% and 78.05 ± 4.2%, respectively) and coating onto tanks (58.6 ± 2.1% and 61.2 ± 2.7%, respectively) at 1 mg mL?1 while least percentage of hatching was recorded in Ag‐TiO2 nanoparticles irrespective of its concentration & mode of supplementation. Highest survival of L. rohita fry (50.13 ± 2.2%) was observed after 15 days post hatching in CuO coated tanks followed by ZnO coated tanks (38.6 ± 2.8%) while least was recorded in Ag‐TiO2 coated tanks (22.53 ± 3.0%). However in control tanks coated with Poly‐Urethane base with hardener and uncoated control tanks, the survival was 42.4 ± 1.2% and 41.36 ± 1.8% respectively. Further, significantly lower microbial load of water was recorded in CuO nanoparticles coated tanks (1.5 × 1010 CFU L?1) as compared to uncoated control tanks (1.1 × 1016 CFU L?1) without affecting water quality parameters. On the other hand, in Ag‐TiO2 coated tanks, significantly lower microbial load (1.0 × 106 CFU L?1) as compared to uncoated control tanks at 15 days post hatching was recorded. However, Ag‐TiO2 was toxic to L. rohita larvae & fry both in direct application and coating onto tanks. Considering the beneficial effects of CuO nanoparticle application, it has the scope of being used in a more eco‐friendly way in hatchery operations.  相似文献   

8.
The experiments explored the pharmacokinetics (PK) properties of oxolinic acid (OXA) after oral administration at three dosages (10, 30 and 80 mg/kg) via medicated feed in the shrimp. The results showed that the Cmax values of 4.31, 14.93 and 16.62 mg/L and AUC0–∞ values of 92.61, 252.30 and 364.27 mg hr?1 L?1 were observed at three OXA dosage groups in the haemolymph respectively. In the hepatopancreas, Cmax values of 7.90, 27.23 and 60.51 mg/kg and AUC0–∞ values of 42.01, 133.06 and 219.06 mg hr?1 L?1 were observed at 0.5 hr post administration respectively. In the muscle, Cmax values of 1.62, 5.80 and 7.36 mg/kg and the AUC0–∞ values of 25.64, 98.10 and 134.24 mg hr?1 L?1 were observed at 2 hr post administration respectively. In the gills, Cmax values of 2.87, 8.08 and 12.12 mg/kg and the AUC0–∞ values of 51.38, 118.65 and 206.48 mg hr?1 L?1 were observed at 4 hr post administration respectively. In addition, the in vitro MIC values of OXA at three dosages against 132 strains of Vibrio were examined and showed that the minimum inhibitory concentration (MIC) values for OXA primarily ranged from 0.15–1.25 µg/ml, including eight strains of Vibrio showing MIC values ≥5 µg/ml. The MIC50 and MIC90 values of 132 strains were 0.62 and 1.25 μg/ml respectively. The AUC0–24/MIC90 ratios of Vibrio were 140.4 in 30 mg/kg group. Furthermore, the P‐glycoprotein (P‐gp) expression was determined in shrimp tissues after administration to three dosage groups (10, 30 and 80 mg/kg). The results showed that P‐gp expression was up‐regulated in the hepatopancreas (5.36‐, 13.68‐ and 31.06‐fold respectively) compared with the control group.  相似文献   

9.
Detoxified Jatropha protein isolate (DJPI), prepared from Jatropha seed cake was hydrolysed using Alcalase 2.4L FG. Both DJPI and hydrolysed DJPI (HDJPI) were evaluated as a fish meal (FM) replacement in common carp (Cyprinus carpio L.) diets. The peptide concentration in HDJPI was determined using matrix‐assisted laser desorption ionization‐time of flight mass spectrometer (MALDI‐TOF). Twenty‐two peptides with molecular mass ranging from m/z 906.455 to 1774.943 Da were identified. Fingerlings (45; av. wt. 10.1 ± 0.4 g) were randomly distributed in five groups with three replicates. An 8‐week feeding experiment was conducted to compare the nutritional quality of the HDJPI, DJPI and FM. Fish were fed on iso‐nitrogenous diets: control (FM based protein), J50 (50% of FM protein replaced by DJPI), J75 (75% of FM protein replaced by DJPI), JH50 (50% of FM protein replaced by HDJPI) and JH75 (75% of FM protein replaced by HDJPI). Growth performance was higher for FM fed group compared with the other groups, while nutrient utilization parameters were similar for control and J50 groups and superior (P < 0.05) to J75 and both the HDJPI fed groups. No variation (P > 0.05) was observed in blood albumin and hepatosomatic index among all different groups. Blood urea nitrogen, calcium, sodium and potassium ions in the blood were similar among all five groups.  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.
A 40 days feeding trial with Labeo rohita (rohu) fry was conducted in six outdoor cemented tanks (5m × 4m × 1 m; 6–8 cm soil base) to establish the relative impact of on‐farm grown live Wolffia globosa (a duckweed with crude protein of 28.57%) and a formulated iso‐nitrogenous feed (crude protein 28.37%) on growth performance, survival, health and overall quality of fingerlings. The experimental tanks were dried, limed at 250 kg/ha, filled with ground water and subsequently applied with cow dung (soaked overnight) and mustard oil cake at 1,000 kg/ha and 50 kg/ha respectively. The fry were stocked at 0.3 millions/ha in six prepared tanks, and fed live Wolffia (T1) and formulated feed (T2). Results of the study indicate better performance (p < 0.05) of fry in terms of final mean weight (7.83 g), length (8.82 cm), daily growth index (6.51 g %/day) and survival (89.5%) than those fed on formulated feed. Furthermore, significantly improved (p < 0.05) feed utilization parameters viz. apparent feed conversion ratio (AFCR), apparent protein conversion efficiency (APCE), apparent protein efficiency ratio (APER); haematological parameters viz. total erythrocyte count (TEC), total leucocyte count (TLC), packed cell volume (PCV), plasma glucose and protein of fry were also observed in T1 (live Wolffia). Overall findings from this study hints towards the possible utilization of on‐farm grown live Wolffia as a suitable nutrient source for fry rearing of L. rohita.  相似文献   

12.
In this study, we have tested the effect of seaweed stocking density in an experimental seaweed biofilter using the economically important red seaweed Hydropuntia cornea integrated with the cultivation of the pink shrimp Farfantepenaeus brasiliensis. Nutrient removal efficiency was evaluated in relation to seaweed stocking density (2.5, 4, 6 and 8 g fw L?1). Total ammonia nitrogen (TAN) was the main nitrogen source excreted by F. brasiliensis, with concentrations ranging from 41.6 to 65 μM of NH4+‐N. H. cornea specific growth rates ranged from 0.8 ± 0.2 to 1.4 ± 0.5% day?1 with lowest growth rates at higher seaweed stocking density (8 g fw L?1). Nutrient removal was positively correlated with the cultivation densities in the system. TAN removal efficiency increased from 61 to 88.5% with increasing seaweed stocking density. Changes in the chemical composition of the seaweed were analysed and correlated with nutrient enrichment from shrimp effluent. The red seaweed H. cornea can be cultured and used to remove nutrients from shrimp effluents in an integrated multi‐trophic aquaculture system applied to a closed recirculation system. Recirculation through seaweed biofilters in land‐based intensive aquaculture farms can also be a tool to increase recirculation practices and establish full recirculation aquaculture systems (RAS) with all their known associated benefits.  相似文献   

13.
Allometric growth and ontogeny were studied in thick‐lipped grey mullet Chelon labrosus reared in mesocosms from 1 to 71 day post hatching (dph). Multivariate allometric analysis of morphometric growth distinguished three distinct developmental stanzas separated by two morphometric metamorphosis lengths (Lm1 = 4.46 ± 0.06 mm; Lm2 = 28.56 ± 1.04 mm). Body mass growth also showed three distinct episodes separated by two inflections, correlated with morpho‐functional changes. First episode concerned pre‐flexion larvae and ended around 4.5 mm‐LT (14‐dph), coinciding with estimated Lm1. It was distinguished by reduced growth, but intense morphogenesis and differentiation processes. Organogenesis and allometric changes indicated that development priorities concerned feeding efficiency, by improving detection ability (sensory system development), ingestion capacity (head growth) and assimilation performance (digestive system differentiation), together with respiration efficiency (gill development). Second episode concerned post‐flexion larvae and, ended around 8.6 mm‐LT (25‐dph). It was distinguished by fast growth of trunk and tail, acquisition of adult axial muscle distribution and completion of gill filament development, improving locomotion and oxygenation performances. It corresponded to transition towards metamorphosing stage as indicated by later isometric growth, musculature maturation and acquisition of juvenile phenotype. Metamorphosis seemed to end at Lm2, suggesting to avoid zootechnic handling before this size.  相似文献   

14.
The aim of this study was to assess the chronic effects of a bio‐pesticide (NeemAzal) on some biochemical parameters of grass carp (Ctenopharyngodon idella) under laboratory conditions. At first, 96 h LC50 of the pesticide was determined using probit analysis software and was found to be 0.73 mg L?1 of the active ingredient (azadirachtin) of the pesticide. Fresh fish were then divided into three treatments and a control and were exposed to sublethal concentrations (10%, 20% and 30% of the 96 h LC50 value) of the pesticide for a month. The biochemical examination of the blood showed a remarkable decrease in values of protein, albumin, AST, ALT, ALP and LDH (P < 0.05).  相似文献   

15.
This study investigates the effects of inclusion of low levels of dietary short chain fructooligosacchairde (sc‐FOS) on physiological response and intestinal microbiota of carp (Cyprinus carpio) larvae. After acclimation, fish (550 ± 20 mg) were allocated into nine tanks (40 fish per tank) and triplicate groups were fed a control diet (0%) or diets containing 0.5% and 1% sc‐FOS for 7 weeks. At the end of the experiment, the growth performance parameters (final weight, weight gain, specific growth rate (SGR), food conversion ratio (FCR) and condition factor (CF), survival rate as well as digestive enzyme activities (amylase, lipase and protease), total viable counts of heterotrophic aerobic bacteria (TVC) and lactic acid bacteria (LAB) level in intestinal microbiota were measured. Our results revealed no significant (P > 0.05) effects of sc‐FOS on growth performance and TVC when compared with the control group. However, administration of low levels of dietary sc‐FOS significantly increased digestive enzyme activities (lipase and amylase) and LAB levels (P < 0.05). Also, survival rate was significantly elevated in sc‐FOS fed carp. These results revealed that administration of low levels of sc‐FOS can be considered as a beneficial dietary supplement for larval stage of common carp.  相似文献   

16.
The aim of this study was to determine the biochemical and histopathological effects of indoxacarb on an economic fish species Cyprinus carpio. The fish were divided into four triplicated groups exposed to either of 0% (control), 5% (0.75 mg/L), 10% (1.5 mg/L) or 20% (3 mg/L) of the pesticide LC50. Blood sampling was performed after 7, 14 and 21 days exposure. There were no changes in blood calcium levels at any times. In the indoxacarb‐treated fish, chloride levels decreased at the first and increased at the second sampling compared to the control. In 3 mg/L treatment, phosphorus increased significantly after 7 days compared to the control. Plasma glucose levels decreased significantly at the 7th and 14th days sampling; however, it increased at the 21st day. After 7 days, creatinine level in 3 mg/L treatment was significantly lower than the control; however, the creatinine levels of indoxacarb treatments were higher than the control at the 21st day. The indoxacarb‐treated fish had higher plasma urea levels compared to the control at the 7th day. At the 21st day, plasma urea level at 3 mg/L was significantly lower than the control treatment. Edema, Lamellar curling, hyperplasia, lamellar fusion and hyperaemia were observed in the indoxacarb‐treated fish gill. Tubular necrosis, hematopoietic necrosis, melanomacrophage aggregates, Bowman's capsule edema, glomerulus degeneration and hyperaemia were observed in the indoxacarb‐treated fish kidney. Generally, sublethal concentrations of indoxacarb cause stress, hydromineral imbalance, metabolism alteration and gill and kidney damages in common carp.  相似文献   

17.
Common carp, Cyprinus carpio (13.54 ± 0.48 g), were fed soybean lecithin‐incorporated diets for 8 weeks. After the feeding trials, the different groups of fishes were assessed by survival, growth parameters, digestive enzymes, antioxidant enzyme activities, mucosal immune parameters, etc. The lecithin‐incorporated diets (10–30 g kg–1) helped to increase the weight gain significantly (p < .05) compared with control groups; activity of digestive enzymes was also significantly (p < .05) higher compared with experimental groups. The antioxidant enzymes including catalase and serum superoxide dismutase were significantly (p < .05) higher in the C. carpio fed lecithin‐incorporated feed than the ones fed the control feed. The serum thiobarbituric acid‐reactive substances and serum glutathione peroxidase activity did not differ significantly (p > .05) between control and experimental groups. The positive correlation supported that antibacterial activity was significantly (p < .05) increased with increasing concentration of lecithin in the diets. Among the different mucosal immune parameters, lysozyme, protease and esterase activities were significantly (p < .05) increased with lecithin‐incorporated diets. The results of this study confirm that 20 and 30 g kg–1 lecithin inclusion in diets helped to enhance the activities of digestive enzymes, antioxidant enzymes, antibacterial factors and mucosal immune parameters in C. carpio.  相似文献   

18.
Ammonia is a metabolite of aquatic organisms which might reach deleterious levels in intensive fish farms. The aim of the present study was to determine median lethal concentrations (96‐h LC50) of total ammonia nitrogen (TA‐N) on marbled spinefoot rabbitfish (Siganus rivulatus) and chronic effects of TA‐N on survival, growth and behaviour of juvenile rabbitfish over a 50 day period. In the first experiment, fish were exposed to 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 mg L?1 TA‐N for 96 h and survival evaluated. In the second experiment, 12 fish were stocked per 50‐L tank and treated with one of 0, 2, 4, 6, 8, 10 and 12 mg L?1 TA‐N with three replicate tanks per treatment. Survival and growth were determined and histopathological alterations of gills due to chronic ammonia exposure were studied by light and electron microscopy. The 96‐h LC50 values were 16–18 mg L?1 TA‐N. In the chronic exposure experiment, fish reared in water with 0 mg L?1 TA‐N had 100% survival and had 50% weight increase in 50 days. Fish at 2 and 4 mg L?1 TA‐N all died whilst fish in 6, 8, 10 and 12 mg L?1 TA‐N survived and grew albeit less than in treatment 0 mg L?1. Gills from ammonia treated fish displayed severe histological and ultrastructural alterations including hyperplasia, hypertrophy and fusion of secondary lamellae, aneurysms and presence of pleomorphic altered cells. Chronic exposure to ammonia is deleterious to marbled spinefoot rabbitfish and low concentrations of ammonia appear to kill the fish in <50 days whilst fish can survive for more than 50 days at concentrations between 6 and 12 mg L?1 TA‐N.  相似文献   

19.
This study assessed the effect of cyclical feeding on compensatory growth, nitrogen (N) and phosphorus (P) budgets of juvenile Litopenaeus vannamei. A 36‐day growth trial was performed with four different feeding protocols. The control group (S0) was fed to satiation twice every day during the whole experimental period; treatment groups S1, S2 and S3 were fed by the 9, 5 and 3 cycles of 1:3, 2:5 and 3:9 (fasting days:feeding days) respectively. Fasting in S1, S2 and S3 groups did not change the specific growth rate in wet weight (SGRw), but the feed conversion efficiency (FCE) and protein efficiency ratio (PER) were significantly increased (P < 0.05) in comparison with control. The N and P consumed per unit wet weight gain of shrimp in S1, S2, S3 groups were significantly lower (P < 0.05) than control group by 15.39%, 15.96%, 19.33% for N, and 15.16%, 15.98%, 19.26% for P respectively. The total discharge of N and P (including N and P discharged by faeces (FN/P), non‐faecal excretions (UN/P) and exuviations (EN/P); ) was significantly lower (P < 0.05) in the experiment groups by 19.91–22.07% for N and 18.68–26.37% for P respectively. Overall, the results suggest that the L. vannamei can reach completely compensatory growth, and the total discharge of N and P per unit wet weight gain of L. vannamei significantly decreased by cyclical feeding, which could have a positive effect on the reduced of environmental N and P loading due to the cultured of L. vannamei.  相似文献   

20.
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   

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