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1.
A 12‐week growth trial was conducted in a flow‐through system to determine dietary selenium (Se) requirement for on‐growing gibel carp (initial body weight: 76.2 ± 0.05 g, mean ± SEM). Selenomethionine was supplemented to the basal diet to formulate seven semi‐purified diets containing 0.26, 0.58, 0.72, 1.14, 1.34, 1.73 and 2.09 mg Se kg?1 diet. The results showed that plasma superoxide dismutase (SOD) activity significantly increased when fish were fed with 0.58 mg Se kg?1 diet (P < 0.05) and then decreased at 2.09 mg Se kg?1 diet (P < 0.05). Plasma T‐AOC activity was higher in fish fed with 0.72 mg Se kg?1 diet (P < 0.05) and plasma malondialdehyde (MDA) was higher in fish fed with 0.26 mg Se kg?1 diet (P < 0.05). When fish were fed 1.14 mg Se kg?1 diet, hepatic GSH‐Px, T‐AOC, GSH and CAT activities were significantly higher than those fed with 0.26 mg Se kg?1 diet (P < 0.05). Hepatic superoxide dismutase (SOD) activity was higher at 1.34 mg Se kg?1 diet (P < 0.05). Fish liver Se concentrations were significantly higher when fed with 0.72 mg Se kg?1 diet (P < 0.05) and then kept constant when Se ≥ 0.72 mg kg?1 (P > 0.05). Whole‐body and muscle Se concentrations were higher when fed with 1.34 mg Se kg?1 diet (P < 0.05) and kept a plateau when Se ≥ 1.34 mg kg?1 (P > 0.05). In conclusion, based on broken‐line regression of hepatic Se concentrations, hepatic SOD activity and hepatic T‐AOC activity, dietary Se requirements for on‐growing gibel carp was 0.73 mg kg?1, 1.12 mg kg?1 and 1.19 mg kg?1 diet respectively.  相似文献   

2.
Ethoxyquin (EQ) is the most common synthetic antioxidant used for preventing rancidity in fish foodstuffs. However, literature related to the effects of dietary EQ on performance of fish was limited. The present study was conducted to investigate the effects of EQ on performance and EQ residue in muscle of juvenile Japanese seabass Lateolabrax japonicus and to estimate the optimal EQ concentration in the diet. Graded levels [0 (control), 50, 150, 450 and 1350 mg EQ kg?1 diet] of EQ were added to the basal diet, resulting in five dietary treatments in the experiment. Each diet was fed to triplicate groups of seabass (initial body weight 8.01 ± 0.76 g) for 12 weeks in floating sea cages (1.5 × 1.5 × 2.0 m, 30 fish per cage). Survival ranged from 78.9 to 86.7%, and was irrespective of dietary EQ levels. The specific growth rate (SGR) of fish fed diets supplemented with ≤50 mg kg?1 EQ had significantly (P < 0.05) higher SGR than fish fed diets supplemented with ≥150 mg kg?1 EQ, the highest SGR was observed in fish fed diet with 50 mg kg?1 EQ supplementation. Feed intake (FI) and feed efficiency (FE) were not significantly (P > 0.05) different among dietary treatments. Fish fed diets with 50 and 1350 mg kg?1 EQ had a significant (P < 0.05) lower body lipid content than fish in the control group. Muscle EQ level significantly increased when dietary EQ increased. Optimal EQ concentration estimated by polynomial regression based on maximum growth of juvenile Japanese seabass was 13.78 mg kg?1 diet.  相似文献   

3.
Development of alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus) larvae was evaluated after exposure of embryos to thyroid hormones (TH) by two different methods of administration. For the first method, alligator gar embryos were placed in a water bath with triiodothyronine (T3; 1 ppm for 2 h), and control treatment embryos were placed in a water bath without T3. For the second method, spotted gar adult males and females were injected with different TH during induced spawning: a group was injected with T3 [20 mg kg?1 body weight (BW)], a second group with thyroxine (T4; 20 mg kg?1 BW), a third group with thyroid‐stimulating hormone (TSH; 4 IU kg?1BW) and a control group with dimethyl sulfoxide. Both methods resulted in increases in the concentrations of T3 and T4 in embryos of both species. An increase in the alkaline enzymatic activity of TH‐treated larvae was observed as well as an increase in the RNA:DNA, RNA:Dry weight and DNA:Dry weight ratios at hatching. Some positive effects of TH application were: a significant increase in the hatching rate of spotted gar larvae from TH‐injected parents and a higher percentage of successful spawns. Evenness of larval sizes and a higher survival rate were observed in alligator gar larvae. Snout development was accelerated by TH treatment in both species.  相似文献   

4.
To study the effects of manganese on growth performance, digestive and absorptive abilities, as well as the antioxidative capacity in the hepatopancreas and intestine, young grass carp (Ctenopharyngodon idellus Val.) (264 ± 1 g) were fed diets containing graded levels of manganese at 3.65 (control), 8.62, 13.48, 18.24, 22.97 and 27.86 mg kg?1 diet for 8 weeks. Per cent weight gain (PWG) and feed intake were the poorest in fish fed the basal diet (P < 0.05). The activities of trypsin, lipase and alkaline phosphatase in the intestine were significantly enhanced with dietary manganese level at 13.48 mg kg?1 diet (P < 0.05). Additionally, in the hepatopancreas and intestine, the protein carbonyl and malondialdehyde contents were the lowest in fish fed the diet with dietary manganese level at 13.48 mg kg?1 diet (P < 0.05), while the anti‐hydroxyl radical capacities, manganese superoxide dismutase (MnSOD), glutathione peroxidase and glutathione‐S‐transferase activities were significantly enhanced with dietary manganese level at 13.48 mg kg?1 diet (P < 0.05). Moreover, the catalase activity and glutathione content in the intestine were the highest in fish fed the diet with dietary manganese level at 18.24 mg kg?1 diet (P < 0.05). These results indicated that optimum dietary manganese promoted growth, enhanced the digestive and absorptive abilities, and improved the antioxidative capacity in young grass carp. Based on the quadratic regression analysis for PWG and intestinal MnSOD activity, the manganese requirements for young grass carp with the initial body weight of 264 g were 16.91 and 18.21 mg kg?1 diet respectively.  相似文献   

5.
This experiment was conducted to study the effects of different forms and levels of manganese (Mn) on the growth performance, antioxidant activities, tissue Mn content and cytosolic manganese superoxide dismutase (cMnSOD) gene expression of Litopenaeus vannamei. Treatments consisted of 0, 10, 20, 30, 40 and 60 mg Mn kg?1 from manganese sulphate (Mn‐S) and manganese methionine (Mn‐Met), providing the actual dietary value of 5.17, 15.62, 25.55, 34.22, 44.48 and 67.90 mg Mn kg?1 Mn‐S, and 5.17, 15.71, 25.36, 35.86, 45.16 and 65.06 mg Mn kg?1 Mn‐Met, respectively. Each diet was fed to triplicate groups of L. vannamei (initial body weight: 1.925 ± 0.002 g) in a recirculated fresh water rearing system for 8 weeks. Weight gain rate (WGR) increased in prawns provided with from 25.55 to 44.48 mg Mn kg?1 Mn‐S and 15.71 to 45.16 mg Mn kg?1 Mn‐Met and then declined above these levels. The lowest protein efficiency ratio (PER) and the highest feed conversion rate (FCR) were observed in prawns fed the control diet (P < 0.05) and showed no significant differences among other treatments (P > 0.05). Survival rate (SR) was not affected by the dietary treatments (P > 0.05). Total SOD and Mn‐SOD activities were higher in the hepatopancreas of prawns fed with Mn‐supplemented diets from 15.71 to 44.48 mg Mn kg?1 (P < 0.05). On the contrary, malondialdehyde (MDA) content was lower in the hepatopancreas of prawns fed the basal diet (P < 0.05). Mn concentrations in the hepatopancreas and muscles increased with increasing levels of dietary Mn supplementation. Moreover, Mn accumulation was lower in the muscle than in the hepatopancreas of the prawns. The mRNA expression of cMnSOD gene in the hepatopancreas of prawns was upregulated with increasing dietary Mn levels of Mn‐S from 25.55 to 44.48 mg Mn kg?1, Mn‐Met from 15.71 to 45.16 mg Mn kg?1 and then plateaued above these levels. Broken‐line regression analysis of WGR indicated that the optimal dietary Mn requirements for juvenile L. vannamei were 32.26 mg Mn kg?1 Mn‐S and 23.90 mg Mn kg?1 Mn‐Met, respectively.  相似文献   

6.
Jundiá (Rhamdia quelen) is an important species for aquaculture in temperate and subtropical climates. In the present study, the results of different forms of GnRH analogue treatments on ovulation in jundiá have been compared with those from treatment with carp pituitary. Seven out of eight females ovulated in groups treated with carp pituitary (4.0 mg kg?1 BW) and Ovaprim (0.5 mL kg?1 BW). Injection with sGnRHa (10 μg kg?1 BW) combined with metoclopramide (20 mg kg?1 BW) caused a significantly lower rate of ovulation with three out of eight females responding. None of the fish injected with sGnRHa (10 μg kg?1 BW) alone ovulated. Mean PGSI [(weight of stripped egg mass/BW of the female before stripping) × 100] and mean fertilization rate values were high and similar between treatment groups. The obtained results indicate that in jundiá, there is a strong dopamine inhibitory tone on gonadotropin secretion. The gonadotropin releasing activity of sGnRHa can be potentiated by dopamine receptor antagonists and the combined treatment is effective in inducing ovulation. In this regard, domperidone proved to be more potent than metoclopramide.  相似文献   

7.
This study was conducted to determine dietary thiamine requirement of juvenile Sclizothorax prenanti and evaluate the effect of dietary thiamine levels on growth performance, body composition and haemato‐biochemical parameters for this fish species. The seven experimental diets were formulated to contain the graded levels of thiamine (0, 10, 20, 30, 40, 60 and 100 mg kg?1 diet, respectively), providing the actual dietary thiamine values of 0.31 (control), 9.82, 21.49, 29.83, 41.66, 62.24 and 114.58 mg kg?1 diet, respectively. Each diet was assigned to three replicate groups of S. prenanti (initial body weight: 13.46 ± 0.28 g, means ± SD) for 60 days. Increasing dietary thiamine level up to 21.49 mg kg?1 diet increased weight gain rate (WGR), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) (P < 0.05), beyond which they remained nearly unchanged. Similarly, hepatic thiamine concentration and several serum biochemical parameters (transketolase activity, triglyceride and total cholesterol contents) increased with increasing levels of thiamine up to 21.49 mg kg?1 diet (P < 0.05) and, thereafter, remained almost constant. However, no significant differences in body composition (moisture, protein, lipid and ash contents) were found among dietary thiamine treatments (P > 0.05). Analysis by the broken‐line regression of WGR, SGR, FE, PER, hepatic thiamine concentration and serum transketolase activity indicated that dietary thiamine requirements in juvenile S. prenanti were 18.45–25.91 mg kg?1 diet.  相似文献   

8.
To investigate effects of iron (Fe) on growth, haematological parameters, flesh quality and antioxidant status in muscle, young grass carp (Ctenopharyngodon idella) (292.0 ± 3.2 g) were fed graded levels of Fe (20.7, 38.4, 52.8, 79.3, 98.0 and 120.0 mg kg?1 diet) for 8 weeks. Per cent weight gain (PWG) and feed intake were improved with Fe levels up to 52.8 mg kg?1 diet. Serum Fe, erythrocyte counts, haemoglobin (Hb), haematocrit and mean cell haemoglobin increased with optimal Fe levels (38.4–79.3 mg kg?1 diet) (P < 0.05). The muscle protein and lipid contents were increased by dietary Fe, whereas moisture, liquid loss, shear force and hydroxyproline contents followed opposite trends. Malondialdehyde and protein carbonyl contents in muscle were the lowest in fish fed the 52.8 or 79.3 mg Fe kg?1 diet, respectively, while superoxide dismutase, catalase, glutathione‐S‐transferase, glutathione peroxidase and glutathione reductase activities, and glutathione content were increased by Fe levels up to 52.8–79.3 mg kg?1 diet. Results indicated that the optimal Fe improved growth, flesh quality and muscle antioxidant defence of young grass carp. Dietary Fe requirements for PWG, serum Fe and Hb of young grass carp (292–695 g) were 73.5, 72.8 and 69.0 mg kg?1 diet, respectively.  相似文献   

9.
The acceleration of final oocyte maturation and ovulation is recognized as a principal process in Caspian kutum Rutilus frisii kutum, a commercial and valuable species in Caspian Sea. The aim of this study was to evaluate the effects of catecholaminergic pharmaceutics which include Salbutamol (β2‐adrenergic receptor agonist), Metoprolol (β1‐adrenergic receptor antagonist), Clozapine and Olanzapine (the third generation of D4 and D2 dopamine receptor antagonists) which can be more efficient than the first and second generations, in combination with Buserelin ([D‐Ser(tBu)6,Pro9‐NEt]‐GnRHa) and Ovaprim (D‐Ala6,Pro9‐Net)‐sGnRH+Domperidone on ovulation and spawning induction in Caspian kutum. One hundred eight adult females were injected once with Buserelin Acetate (BUS) 5 μg kg?1 BW, Ovaprim 0.5 mL kg?1 BW, Salbutamol Sulphate (SLB) 4 mg kg?1 BW, Olanzapine (OLZ) 5 mg kg?1 BW, Clozapine (CZ) 12 mg kg?1 BW and Metoprolol Tartrate (MTP) 5 mg kg?1 BW, being divided into 12 groups: group 1, intact (negative control); group 2, Ovaprim (positive control); group 3, OLZ+SLB; group 4, OLZ+MTP; group 5, OLZ+BUS; group 6, CZ+SLB; group 7, CZ+MTP; group 8, CZ+BUS; group 9, OLZ+BUS+SLB; group 10, OLZ+BUS+MTP; group 11, CZ+BUS+SLB and group 12, CZ+BUS+MTP (N = 9). The results showed that the highest mean value in ovulation success, ovulation index, fertilization success, relative fecundity and the number of eggs belonged to Ovaprim treatment. On the other hand, spawning was successful in OLZ+BUS+SLB and CZ+BUS treatments (P < 0.05), whereas it was lower in CZ+MTP, CZ+BUS+MTP and OLZ+BUS than the other treatments. Therefore, it could be concluded that Clozapine and Olanzapine potentiated the effect of Buserelin treatment in ovulation and spawning induction, while Metoprolol blocked the stimulatory effects of GnRHa, Clozapine and Olanzapine. Salbutamol also can amplify stimulatory effect of all mentioned pharmaceutics.  相似文献   

10.
The effect of docosahexaenoic acid (DHA) on the growth performance, survival and swim bladder inflation of larval Seriola dumerili during the rotifer feeding period was investigated in two feeding experiments. Amberjack larvae at 3 day post hatching were fed rotifers enriched with (1) freshwater C hlorella (Chlo), (2) a mixture (2:1, v/v) of Chlo and DHA‐enriched C hlorella (DHA‐Chlo), (3) DHA‐Chlo and (4) DHA‐Chlo and commercial DHA emulsion, in triplicate for 7 days. The average DHA contents of the rotifers were 0.0, 0.4, 1.0 and 1.9 mg g?1 DM respectively. The survival rate was improved by the enrichment of rotifers with DHA‐Chlo alone, and DHA‐Chlo and emulsion. Growth and swim bladder inflation of fish fed rotifers enriched with DHA‐Chlo were significantly (P < 0.05) improved, however, with increased levels of DHA further improvement was not found. DHA content in the larval whole body proportionally increased with the DHA level in the rotifers. These results suggest that DHA enrichment of rotifers is effective to improve the growth, survival rate and swim bladder inflation of amberjack larvae. The DHA requirement of amberjack larvae is estimated to be 1.5 mg g?1 on a dry matter basis of rotifers.  相似文献   

11.
Sanguinarine (SA), with antimicrobial and antiparasitic activities against fish pathogens, exhibits great potential commercial use in aquaculture. However, little information on pharmacokinetics of SA restricts further application in aquaculture. In this study, pharmacokinetics of SA in common carp (Cyprinus carpio) following a single intraperitoneal administration [10 mg kg?1 BW (body weight)] was evaluated by high‐performance liquid chromatography (HPLC). The peak concentration (Cmax) of SA in kidney was 11.8 μg g?1, which was higher than in other tissues and plasma. The terminal half‐life in fish tissue and plasma was as follows: 42.3 h (kidney) > 37.2 h (liver) > 20.1 h (gill) > 18.8 h (muscle) > 10.9 h (spleen) > 10.0 h (plasma). Additionally, we determined the bacterial loads in tissues of common carp infected with Aeromonas hydrophila after i.p. administration of SA at 0, 5, 10 and 20 mg kg?1 BW. The results showed that i.p. administration of SA at 10 mg kg?1 BW significantly enhanced antibacterial efficacy against A. hydrophila, where the antibacterial ratio in the gill, kidney, spleen and liver on day 5 was 95.13%, 93.33%, 90.09% and 92.82%, respectively. Overall, these results suggested the potential of SA to treat A. hydrophila infection in common carp farming industry.  相似文献   

12.
Three in vivo experiments were conducted to measure the effectiveness of commercial Bacillus probiotics on survival and development of Litopenaeus vannamei larvae from nauplii 3–4 (N3–4) to zoea 3 (Z3) stages. Experiment I: Nine commercial Bacillus probiotics were individually added to larvae twice at N6 and Z1 at levels of 2, 20, and 100 mg L?1. Only six of nine products at 20 mg L?1 exhibited higher or significantly higher larval survival (P < 0.05) than the control. Experiment II: Two superior products from the first experiment were administered to larvae with six dose frequencies at 20 mg L?1. For both products, three doses, once at each of N3–4, N6 and Z1 stages, yielded the best larval survival and development rates (P < 0.05), and these were confirmed by enhanced activities of tryptase and amylase. Experiment III: The isolates of these two products, identified as Bacillus subtilis and Bacillus licheniformis, were delivered to larvae singly at concentrations of 1.0 × 108 and 1.0 × 109 CFU L?1, or at the same concentrations by mixing the two equally. At 1.0 × 109 CFU L?1, B. subtilis exerted more beneficial effects on larvae than B. licheniformis or the mixture. Therefore, the optimal dosage and dose frequency of commercial Bacillus products should be evaluated prior to large‐scale application in shrimp hatcheries to avoid futility or even adverse effects, as spore counts and non‐bacterial ingredients are key factors influencing the efficacy of Bacillus probiotics.  相似文献   

13.
A 75‐day experiment was conducted with juvenile gibel carp (Carassius auratus gibelio) (4.80 ± 0.01 g) to evaluate effects of dietary chitosan on fish growth performance, haematology, intestine morphology and immune response. Six isonitrogenous (crude protein: 383 g kg?1), isolipid (97.5 g kg?1) and isocaloric (gross energy: 16.7 kJ g?1) diets were formulated to contain 0, 1800, 4000, 7500, 10 000, 20 000 mg kg?1 chitosan, respectively. The results showed that the growth was depressed when the fish fed with 10 000 mg kg?1 chitosan. Serum cholesterol, triglyceride and low‐density lipoprotein decreased in 10 000 and 20 000 mg kg?1 chitosan. On day 75, blood leucocyte phagocytic activity respiratory burst and alternative pathway of complement haemolytic activity were enhanced in 4000 mg kg?1 chitosan. The number of goblet cell, intraepithelial lymphocyte of mid‐intestine and microvilli height of distal intestine increased at 4000 mg kg?1 dietary chitosan. Dietary chitosan modulated intestine microbiota, depressed pathogen bacteria Aeromonas veronii‐like and improved Cellulomonas hominis‐like, Bacillus oceanisediminis‐like and two uncultured bacterium‐like species on day 75. Dietary 7500 and 10 000 mg kg?1 chitosan enhanced the protection against Aeromonas hydrophila infection. In conclusion, oral administration of dietary 7500 mg kg?1 chitosan for 75 days is recommended for the survival of gibel carp.  相似文献   

14.
This study evaluated the effects of basil (Ocimum basilicum) leaves extract supplement on growth, blood parameters and resistance to Aeromonas hydrophila in Cyprinus carpio fingerlings. Basil leaves were mixed thoroughly with feed at 0, 100, 200, 400, 800 and 1600 mg kg?1 of diet and were fed in triplicate group for 2 months. At the end of this period, growth performance and survival were determined. Then fish were challenged intraperitoneally with A. hydrophila and mortalities were recorded up to 10 days post challenge. Results indicated that WBC, RBC, Ht, Hb, total protein, albumin and globulin were higher (P < 0.05) in fish fed diets containing O. basilicum compared with the control. Highest specific growth rate values were observed in 400 mg kg?1 group. Feed conversion ratio was significantly lower (P < 0.05) in fingerlings fed 400 and 800 mg O. basilicum kg?1 dry diet. After 10 days post challenge, total protein, WBC, RBC and Hb were significantly higher in 400 mg kg?1 compared with other groups. These results reveal that a dietary O. basilicum leaves extract of 400 mg kg?1 fed for 60 days leads to increased growth performance and survival rate as well as improved feeding efficiency in common carp fingerlings rendering them more resistant against infection by A. hydrophila.  相似文献   

15.
A 9‐week feeding trial was conducted to determine the optimal dietary vitamin C requirement and its effects on serum enzymes activities and bacterial resistance in the juvenile yellow drum Nibea albiflora (initial weight 33.2 ± 0.10 g). Six practical diets were formulated containing vitamin C 2.1, 45.3, 89.6, 132.4, 178.6 and 547.1 mg kg?1 diet supplied as l ‐ascorbyl‐2‐monophosphate. The fish fed 547.1 mg kg?1 diet showed a significantly higher survival than that fed 2.1 mg kg?1 diet. The weight gains and specific growth rate of the fish fed 2.1 mg kg?1 diet were significantly lower than those of the fish fed 89.6–547.1 mg kg?1 diets. The liver vitamin C concentration firstly increased with increasing dietary vitamin C supply from 2.1 to 178.6 mg kg?1 diet and then stabilized. The serum superoxide dismutase activities of the fish fed 547.1 mg kg?1 diet were significantly lower than those of the fish fed 2.1–89.6 mg kg?1 diet. The fish fed 2.1 mg kg?1 diet had a significantly higher alkaline phosphatase activity than those in the other groups except the 45.3 mg kg?1 group. Fish that received diets containing vitamin C at 547.1 mg kg?1 had significantly higher nitro blue tetrazolium and lysozyme activity, and fish that received diets containing vitamin C at 45.3–547.1 mg kg?1 exhibited resistance against Vibrio alginolyticus infection. The dietary vitamin C requirement of the juvenile yellow drum was established based on broken‐line model of weight gain to be 142.2 mg l ‐ascorbyl‐2‐monophosphate kg?1 diet.  相似文献   

16.
To investigate the effects of niacin on growth, digestion and absorption capacity, and the potential mechanism for digestive and brush border enzyme activities, grass carp (Ctenopharyngodon idella) (256 ± 0.41 g) were fed diets containing 3.95 (basal diet group), 14.92, 24.98, 35.03, 44.97 and 55.01 mg niacin kg?1 diet for 8 weeks. Results indicated that percentage weight gain (PWG), feed intake and feed efficiency were the lowest in basal group (P < 0.05). Similarly, niacin deficiency decreased hepatopancreas trypsin, chymotrypsin, lipase and amylase activities (P < 0.05), intestinal Na+, K+‐ATPase, alkaline phosphatase, γ‐glutamyl transpeptidase and creatine kinase (CK) activities, the cholecystokinin (CCK) content in proximal intestine (PI) and growth hormone content in serum (P < 0.05). Furthermore, niacin deficiency downregulated gene expression of hepatopancreas trypsinogen 1, trypsinogen 2, chymotrypsinogen and amylase, intestinal Na+, K+‐ATPase alpha subunit isoform 1, Na+, K+‐ATPase alpha subunit isoform 8 and CK, and target of rapamycin (TOR) and S6 kinase 1 (S6K1) of hepatopancreas and intestine (P < 0.05), whereas upregulated eIF4E‐binding protein (4EBP) gene expression (P < 0.05). The niacin requirement for young grass carp (256–689 g) based on PWG, hepatopancreas trypsin activity and Na+, K+‐ATPase in PI was 34.01, 35.10 and 42.08 mg kg?1 diet, respectively.  相似文献   

17.
The administration of antimicrobials to control bacterial pathologies in Chilean scallop hatcheries is a frequent practice, but their effects on these cultures remained unknown. This study was undertaken to obtain information on the effect of the administration of florfenicol and oxytetracycline on the growth, survival and bacterial content of scallop larvae under farming conditions. Florfenicol‐treated cultures exhibited high survival rates (44% after 17 days of culture), whereas cultures not treated or treated with oxytetracycline collapsed after 11 days of culture. Surprisingly, no significant differences in the heterotrophic (Tukey test; P = 0.226) and Vibrio (Tukey test; P = 0.666) concentrations between the oxytetracycline‐treated and untreated larval cultures were observed. Otherwise, florfenicol administered directly into rearing tanks produced significantly higher larval growth (Tukey test; P = 0.0001) and survival (Tukey test; P = 0.011) than bath treatment. When 2 and 4 mg L?1 of florfenicol were compared, no significant differences in growth (t‐test; P = 0.4596) and survival (Tukey test; P = 0.057) were observed, suggesting that a concentration of 2 mg L?1 is sufficient to ensure larval production. The present results demonstrate the efficacy of florfenicol‐based therapy to increase larval survival and growth at commercial scale and prompt the necessity to standardize its use in Chilean scallop hatcheries.  相似文献   

18.
This study evaluated the effects of diet containing 0 (C: control), 75 (D1), 100 (D2), 125 (D3) and 150 (D4) mg kg?1 F. vulgare essential oil on growth and reproductive performance of C. nigrofasciatum. A total of 225 Convict cichlids female with mean weight (1.65 ± 0.02 g) were distributed into 15 glass aquaria (15 fish tank?1) in triplicate treatments. During 40 days of experimental period, fish fed at 3% of their body weight daily. At the end of experiment, growth indices, gonadosomatic index and reproductive indices were determined. The best feed conversion ratio was obtained in D4 (1.19 ± 0.03, P < 0.05). The addition of F. vulgare essential oil did not have any statistical effects on other growth indices (specific growth rate, weight gain and condition factor). Total survival rates in all treatments and control were uniformly high, ranging from 93% to 97% (P > 0.05). F. vulgare essential oil has no negative effect on survival rate of C. nigrofasciatum. There were no significant differences among protein content of fish body (P > 0.05). The lowest value of fat content (26.5 ± 0.5%) was observed in D2, and it had significant difference with control and other groups (P < 0.05). The ash percentage in treatments fed with F. vulgare essential oil were higher than control fish (P < 0.05). The highest moisture content was detected in D4 (72.68 ± 0.19%) and D2 (71.23 ± 2%) groups. Among the used dosage, D4 was the most effective dosage that could significantly increase GSI (11.06 ± 1.55%), fecundity (340 ± 21) and hatching ratio (92.33 ± 1.63%). There were no significant differences in diameter of eggs among various treatments (P > 0.05).  相似文献   

19.
An 8‐week study was conducted to determine folic acid requirement and its effect on antioxidant capacity and immunity in juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853), followed by a challenge assay with the pathogen Aeromonas hydrophila for 2 weeks. Folic acid was added to a basal diet at seven levels (0, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0 mg folic acid kg?1 diet), and a diet free of folic acid and vitamin B12 was also included as a control. Crabs were fed twice daily in 32 tanks with 7.76–8.17 mg oxygen L?1, 25.0–31.0 °C and 7.5–8.3 pH. Growth and feed efficiency were significantly greater in crabs fed ≥2.0 mg folic acid kg?1, but not significantly different between crabs fed diets >2.0 mg folic acid. The superoxide dismutase activity and glutathione S‐transferase activity were highest in crabs fed ≥2.0 mg folic acid kg?1, followed by those fed 0.5 and 1.0 mg folic acid kg?1, and the control diet. The malondialdehyde content was highest in crabs fed the control diet, followed by those fed 0 mg folic acid kg?1, and the lowest value occurred in those fed ≥0.5 mg folic acid kg?1. Phenoloxidase activity and total haemocytes were significantly higher in crabs fed ≥2.0 mg folic acid kg?1 than other diets. Crabs fed 2.0 mg folic acid kg?1 had the highest lysozyme, acid phosphatase and alkaline phosphatase activities but the lowest cumulative mortality. The optimum dietary folic acid requirement by E. sinensis was estimated at 2.29–2.90 mg kg?1 diet.  相似文献   

20.
Two 8‐week growth trials were conducted in indoor recirculation system to evaluate the protein requirements for juvenile (3.70 ± 0.20 g) and pre‐adult (85.2 ± 0.70 g) gibel carp, Carassius auratus gibelio var. CAS III. Six isoenergetic diets were formulated for each trial using fish meal and casein as protein sources, and protein level was 250–450 g kg?1 in Trial 1 and 200–450 g kg?1 in Trial 2. With the increasing dietary protein, feeding rate (FR) and feed conversion ratio (FCR) significantly decreased (P < 0.05). Weight gain (WG) increased first and then reached a plateau in 330–450 g kg?1 in Trial 1 (P > 0.05), while decreased after the maximum value in 350 g kg?1 in Trial 2 (P < 0.05). Productive protein values (PPVs) were lower in 370–450 g kg?1 in Trial 1 and 400–450 g kg?1 in Trial 2 (P < 0.05). Increasing dietary protein level increased protein content and decreased lipid content in whole fish body and white muscle (P < 0.05). Apparent digestibility coefficient of dry matters (ADCd) decreased, while apparent digestibility coefficient of protein (ADCp) increased in 370–450 g kg?1 in Trial 1 and 250–450 g kg?1 in Trial 2 (P < 0.05). Trypsin activity significantly increased in 370–450 g kg?1 in Trial 1 (P < 0.05) and was not affected in Trial 2 (P > 0.05). Hepatic alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in both trials increased when dietary protein was above 400 g kg?1 (P < 0.05). Based on quadratic regression of WG, it was estimated that dietary protein requirement for maximum growth was 414 g kg?1 (digestible protein of 376 g kg?1) and 365 g kg?1 (digestible protein of 324 g kg?1) for juvenile (3.70 g) and pre‐adult gibel carp (85.2 g).  相似文献   

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