Streptococcus iniae infection and tissue distribution in hybrid striped bass (Morone chrysops×Morone saxatilis) following inoculation of the gills

This study was designed to test the possibility that Streptococcus iniae enters through the gills and causes infection in hybrid striped bass. To determine the dose response, four groups of fish were inoculated with S. iniae via the gills with a dose of 5.0×10⁵, 2.6×10⁶, 5.0×10⁶, or 1.0×10⁸ CFU/fish. One group of fish was inoculated with tryptic soy broth (TSB) via the gills to serve as controls. The cumulative percent mortality was 13%, 27%, 100% and 100% for 5.0×10⁵, 2.6×10⁶, 5.0×10⁶ and 1.0×10⁸ CFU/fish, respectively. We also examined the tissue dissemination of S. iniae at 0.5, 4, 8, 12, 24, 48 and 72 h after experimental gill inoculation. Fish were inoculated with 2.6×10⁶ or 5.0×10⁶ CFU/fish, which caused low and high mortality, respectively. Within 48 h, fish inoculated with the 2.6×10⁶ dose were culture positive on the gill surface, blood of the first and second gill arches, blood of the third and fourth gill arches and the nares. However, for the dose of 5.0×10⁶ CFU/fish, S. iniae was also isolated from the olfactory, optic and cerebellum regions of the brain, eye, head kidney, trunk kidney, spleen and liver at 48 h. For the 2.6×10⁶ dose, S. iniae was not isolated until 48 h post-inoculation, but was isolated at 12 h for the 5.0×10⁶ dose. The results of this study indicate that S. iniae can enter hybrid striped bass through the gills. However, mortality at similar S. iniae doses was lower than we previously observed by inoculation of the nares.     

Dietary threonine requirement of juvenile hybrid striped bass (Morone chrysops♀×M. saxatilis♂)

Two growth studies were conducted to determine the dietary threonine requirement of reciprocal cross hybrid striped (sunshine) bass. Semipurified diets were prepared with crystalline amino acids and lyophilized fish muscle to supply 350 g crude protein kg⁻¹ diet. The basal diet contained 4.9 g threonine kg⁻¹ from fish muscle, and test diets were supplemented with graded levels of L-threonine. In the first experiment, fish initially averaging ≊ 9.8 g each were fed diets containing threonine levels of 4.9, 7.5, 10.0, 12.5, 15.0 and 17.5 g kg⁻¹ dry diet for 7 weeks. Weight gain, feed efficiency and protein efficiency ratio (PER) were significantly ( P < 0.01) influenced by dietary threonine level. Based on weight-gain responses, a threonine requirement (± SE) of 8.4 (± 0.8) g kg⁻¹ dry diet was determined, and dietary threonine levels of 10.0 g kg⁻¹ diet or greater resulted in the highest levels of free threonine in plasma.
Based on the results of the first experiment, a second feeding trial was conducted with diets containing threonine levels of 4.9, 6.5, 8.0, 9.5, 11.0 and 12.5 g kg⁻¹ dry diet. Fish initially averaging ≊ 3.0 g each were fed each diet for 8 weeks. Weight gain, feed efficiency and PER values of fish were markedly improved, with increases in dietary threonine up to 8.0 g kg⁻¹ dry diet. Regression analysis of weight gain, feed efficiency and PER data using the broken-line model resulted in threonine requirement estimates of 9.7, 8.5 and 8.6 g kg⁻¹ dry diet, respectively. Based on these data, the threonine requirement of juvenile sunshine bass was determined to be ≊ 9.0 g kg⁻¹ dry diet or 26 g kg⁻¹ of dietary protein.     

Dietary tryptophan requirement of hybrid striped bass (Morone chrysops × M. saxatilis)

Requirements for six of the 10 indispensable amino acids (IAA) have not been quantified for hybrid striped bass. In this study, we estimate the requirement for l ‐tryptophan by nonlinear regression analysis of several growth indicators. Fifteen isocaloric, isonitrogenous diets were formulated to contain 1.0, 1.3, 1.6, 1.9, 2.2, 2.5, 2.8, 3.1, 3.4, 3.7, 4.0, 5.0, 6.0, 10.0 or 14 g l ‐tryptophan kg^?1 diet and fed to reciprocal cross hybrid striped bass for 7 weeks. After 5 weeks, survival of fish receiving the basal diet was 40% while surviving fish fed this diet were in poor health. Survival of fish receiving 1.3 g Trp kg^?1 diet declined to 70% by termination of the trial. Survival in other treatments was 100%. Fish weight gain was 100% or greater for fish receiving 1.6 g Trp kg^?1 diet or more. Hepatosomatic index, muscle ratio and intraperitoneal fat (IPF) ratio also responded to dietary tryptophan concentration. IPF was inversely related to dietary tryptophan concentration. The dietary tryptophan requirement was estimated to be between 2.1 and 2.5 g kg^?1 diet (6–7 g kg^?1 protein), depending on response variable, using four‐ and five‐parameter saturation kinetics models. These findings will increase the precision of diets formulated for hybrid striped bass.     

Effects of cyclic feeding on compensatory growth of hybrid striped bass (Morone chrysops×M. saxitilis) foodfish and water quality in production ponds

An 18‐week study was conducted in 12, 0.1 ha ponds to evaluate the impacts of cyclic feeding regimes on hybrid striped bass (HSB) foodfish production and pond water quality. Approximately 840 HSB [mean weight (std.); 91.08 g (8.18)] were stocked into each pond (8400 fish ha^?1; 3360 fish acre^?1) and fed according to one of three feeding regimes. The three feeding regimes included a control (fed twice daily to apparent satiation), and cycles of 3 weeks feed deprivation followed by 3 or 6 weeks of feeding to apparent satiation (3/3 and 3/6 respectively). Compensatory growth (CG) was observed in both cyclic feeding treatments; however, the response was insufficient for the fish to completely regain lost weight. Final mean weight of control fish (477.9 g) exceeded (P<0.05) that of fish receiving the two cyclic treatments: 3/6 (404.7 g) and 3/3 (353.8 g). Specific growth rate (SGR) of fish in the 3/3 treatment increased during all three refeeding periods, and was significantly greater than controls during weeks 9–12 and weeks 15–18, which represent the refeeding phase of the second and third feeding cycles. Specific growth rate for fish in the 3/6 treatment was significantly higher than controls only during the first 3 weeks of the first feeding cycle. Hepatosomatic index and condition factor were highly responsive measures that closely followed the metabolic state of fish on the feeding cycle. Of the water quality variables measured, total phosphorus was 32% lower in ponds receiving cyclic feeding versus control ponds. Soluble reactive phosphorus was 41% and 24% lower in ponds offered the 3/3 and 3/6 cyclic feeding treatments, respectively, although, significant differences (P<0.10) were only observed between control and 3/3 treatment ponds. Overall, CG was observed in HSB foodfish grown in ponds, although 3 weeks of feed deprivation was excessive and did not allow for complete growth compensation. Weight loss during feed deprivation was influenced by pond water temperatures. Early season feed deprivation did not cause as much weight loss as during the second cycle later in the season. Further studies on shorter deprivation periods applied during moderate to low water temperatures are needed to identify feeding regimes that minimize weight loss and result in a complete CG response.     

Dietary vitamin E requirement of hybrid striped bass (Morone chrysops female × M. saxatilis male)

This study was conducted to determine the dietary vitamin E requirement of juvenile hybrid striped bass ( Morone chrysops female ×  Morone saxatilis male). Semi-purified diets supplemented with 0.2 mg Se kg⁻¹ from Na₂SeO₃ and either 0 (basal), 10, 20, 40, 60, or 80 mg vitamin E kg⁻¹ as  DL -α-tocopheryl acetate were fed to hybrid striped bass initially averaging 1.8 ± 0.1 g (mean ± SD) for 12 weeks. Fish fed the basal diet, which contained 5.8 mg α-tocopherol kg⁻¹ dry weight, were darker in colour and had reduced weight gain, as well as generally reduced haematocrit values compared with fish fed diets supplemented with vitamin E. In addition, fish fed diets containing less than 20 mg supplemental vitamin E kg⁻¹ had significantly ( P  < 0.05) reduced weight gain and feed efficiency compared with those fed diets supplemented with vitamin E at 20–80 mg kg⁻¹. Dietary supplementation of vitamin E caused incremental increases in the concentration of α-tocopherol in both plasma and liver tissues. However, hybrid striped bass fed graded levels of vitamin E did not exhibit a dose response in terms of ascorbic acid-stimulated lipid peroxidation of hepatic microsomes. Regression analysis of weight gain data using the broken-line model indicated a minimum vitamin E requirement ( ±  SE) of 28 ( ±  3) mg kg⁻¹ dry diet. Based on these data, the dietary vitamin E requirement of hybrid striped bass appears to be similar to that determined for other fish species.     

Hypoxia affects performance traits and body composition of juvenile hybrid striped bass (Morone chrysops × M. saxatilis)

Performance traits and body composition of juvenile hybrid striped bass (Morone chrysops × M. saxatilis) in response to hypoxia were evaluated in replicate tanks maintained at constant dissolved oxygen concentrations that averaged 23.0 ± 2.3%, 39.7 ± 3.0% and 105.5 ± 9.5% dissolved oxygen saturation. Fish were fed a commercially formulated feed daily to apparent satiation. Total feed intake and fish growth and yield increased linearly in response to increased dissolved oxygen concentration. Nutrient utilization was reduced significantly only at the greatest level of hypoxia. With the exception of whole body protein content, whole body compositional indices and nutrient retention efficiencies were linearly related to dissolved oxygen concentration. Results demonstrate that as hypoxia becomes more severe, juvenile hybrid striped bass feed intake is reduced, which affects growth and nutrient retention.     

大口黑鲈幼鱼对饲料中锌的需求量

为确定大口黑鲈幼鱼对饲料锌的适宜需求量,以酪蛋白、明胶和鱼粉为主要蛋白质源,以ZnSO_4·H_2O为锌源制作半精制基础饲料,分别向基础饲料中添加0、25、50、100和200 mg/kg锌,制成5种含不同锌水平饲料(24.8、48.8、78.9、126.1和223.6 mg/kg干物质)(命名为Zn-25、Zn-49、Zn-79、Zn-126和Zn-224),投喂初始体质量为(10.99±0.07) g的大口黑鲈幼鱼8周。结果显示,饲料中补充25 mg/kg锌(Zn-49)显著提高了大口黑鲈增重率,降低了饲料系数,进一步提高锌的添加量后,各组增重率和饲料系数趋于稳定。当饲料锌含量为25～49 mg/kg时,T-SOD和CuZn-SOD活性增加,锌含量达到49 mg/kg后,其活性保持基本稳定,而AKP活性在Zn-79组最高。大口黑鲈全鱼和脊椎骨中的锌含量随饲料中锌含量的增加而上升,当饲料锌含量达到126 mg/kg (Zn-126)后,全鱼和脊椎骨中的锌含量不再显著增加,而全鱼铁、骨铁、骨锰含量和全鱼铁、锌沉积率则随饲料锌含量的增加而下降。研究表明,在半精制饲料中补充锌可以显著改善大口黑鲈的生长和饲料利用,提高血清免疫能力、全鱼锌和骨锌的沉积,以增重率、饲料系数、全鱼锌和骨锌为指标,基于折线模型确定大口黑鲈幼鱼对饲料中锌的需求量分别为45.5、44.6、121.8和130.5 mg/kg干物质。     

Beneficial effects of n-3HUFA enriched Artemia as food for larval palmetto bass (Morone saxatilis × M. chrysops)

The beneficial effects of feeding n−3 highly unsaturated fatty acids (HUFA ≥ 20 carbon fatty acids with three or more double bonds) to palmetto bass (striped bass × white bass) larvae, 4–30 days of age, were studied using Artemia diets enriched with six n-3HUFA levels. Dietary n-3HUFA concentrations were < 0.03% (control diet), 0.33%, 0.63%, 0.87%, 1.26%, and 2.27% of dry-wt Artemia. Larval n-3HUFA contents were reduced at a faster rate with decreasing dietary n-3HUFA intake, and were significantly different by 30 days posthatch (4–20 mg g⁻¹ dry-wt fish). Starved larvae selectively conserved endogenous n-3HUFA reserves, indicating an essential role of n-3HUFA in larval development. Mass mortality in the control and 0.33% n-3HUFA diets occurred at metamorphosis (26–28 days posthatch). At harvest, all fish, except those fed the two highest n-3HUFA diets, suffered from handling stress (shock syndrome) with increasing severity (25 to 100%) at decreasing dietary n-3HUFA intake. Recovery from shock syndrome was 100% at the 0.63% and 0.87% n-3HUFA diets, 63% at the 0.33% n-3HUFA diet and 0% at the control diet. Post-harvest survival was similar among the four highest dietary n-3HUFA groups (64–73%), whereas the two lowest n-3HUFA groups differed significantly (0 and 37%). Growth promotion was evident with increased dietary n-3HUFA intake as fish fed the highest n-3HUFA diet were twice the size of those fed the control diet (99 vs 52 mg wet-wt). Final fish sizes at the three highest n-3HUFA diets were similar. Given similar culture conditions, a minimum dietary n-3HUFA intake of 1.26% of dry-wt Artermia is recommended to avoid handling stress and promote growth in larval palmetto bass.     

Total aromatic amino acid requirement of juvenile grass carp (Ctenopharyngodon idella)

This experiment was conducted to investigate total aromatic amino acid requirement of juvenile grass carp Ctenopharyngodon idella. Six isonitrogenous and isoenergetic semipurified diets containing casein and gelatin with graded level of phenylalanine (7.8, 11.1, 14.4, 17.6, 21.7, 24.9 g kg^?1 DM) were formulated. Each diet was randomly assigned to triplicate group of 30 fish (3.58 ± 0.002 g, mean ± SEM) each tank for 8 weeks. The highest weight gain (WG, %), final body weight (g) and specific growth rate were recorded when phenylalanine level was 17.6 g kg^?1 of the diet. Fish muscle protein content, protein efficiency ratio (PER), feed conversion ratio and alanine aminotransferase were significantly affected by dietary phenylalanine level. The polynomial regression calculated using WG and PER indicated that the optimal dietary total aromatic amino acid (phenylalanine + tyrosine) requirement for juvenile grass carp was 24.4 g kg^?1 of the diet, corresponding to 65.9 g kg^?1 of dietary protein.     

Refined understanding of sulphur amino acid nutrition in hybrid striped bass, Morone chrysops♀×M. saxatilis♂

Previous studies have indicated that the level of total sulphur amino acids (TSAA) (methionine+cystine) is most limiting in practical diet formulations for hybrid striped bass (HSB), especially if animal feedstuffs are replaced with plant feedstuffs. Reduction in costly animal feedstuffs such as fish meal, while maintaining adequate dietary levels of TSAA, may enhance the cost effectiveness of production. Therefore, this study investigated three different aspects of sulphur amino acid nutrition of HSB including: (1) the efficacy of crystalline methionine hydroxy analogue (MHA) and liquid MHA (Alimet?) relative to l‐ methionine in meeting the requirement for TSAA; (2) the cystine‐sparing value for methionine; and (3) the influence of various sulphur amino acid supplements on ammonia excretion. During three separate feeding trials (2, 6 and 10 weeks in duration), juvenile HSB were fed various diets including a basal diet deficient in TSAA (0.33% or 0.51% of diet), and experimental diets supplemented on an equal‐sulphur basis with different levels of either l‐ methionine, Alimet? or crystalline MHA. Diets containing TSAA at 1% of diet and different ratios of cystine to methionine (60:40, 55:45, 50:50 and 45:55) were also fed to re‐evaluate the sparing effects of cystine on methionine. In trial 1, over the course of 10 weeks, Alimet? was 73% as effective in promoting weight gain as l ‐methionine at the same concentration while MHA was 83% as effective. After 6 weeks in trial 2, fish fed Alimet? at 1.25% of diet displayed similar growth performance as those fed TSAA at 1.0% of diet, while weight gain of fish fed Alimet? at 1% was only 58% of that displayed by fish fed TSAA at 1.0%. No significant differences in weight gain, feed utilization or survival were observed among fish fed diets containing various ratios of cystine to methionine, although the diet with 60:40 cystine to methionine had the lowest numerical responses. Inclusion of MHA or Alimet? did not affect TAN excretion of HSB. These findings will aid in refining diet formulations for HSB to ensure adequate sulphur amino acid nutrition.     

大口黑鲈幼鱼对饲料中锰的需求量

为确定大口黑鲈幼鱼对饲料中锰的需求量,在含锰5.2 mg/kg的半精制饲料中分别添加0、4、8、16、32和64 mg/kg锰(以MnSO₄·H₂O形式),制成6种不同锰水平的饲料(5.2、9.6、13.5、20.7、 38.3和67.9 mg/kg),投喂初始体重(16.00±0.07) g的大口黑鲈幼鱼10周。结果显示,在基础饲料中添加锰,可显著提高大口黑鲈幼鱼的增重率,降低饲料系数,各组增重率与饲料系数在锰含量达到13.5 mg/kg后基本稳定。随饲料中锰含量的增加,血清T-SOD、Mn-SOD活性和全鱼、脊椎骨中的锰含量上升,并在饲料锰含量达到20.7mg/kg后趋于稳定,而血清丙二醛含量则表现为下降的趋势。全鱼铁、骨铁、骨锌和全鱼锰沉积率随饲料锰含量的增加而下降。研究表明,在半精制饲料中补充锰可以促进大口黑鲈幼鱼生长、提高饲料利用率、血清抗氧化能力、全鱼和骨锰的沉积。以增重率、饲料系数、全鱼锰和骨锰为评价指标,经折线回归分析,大口黑鲈幼鱼对饲料中锰的需求量分别为18.3、20.5、21.1和23.4 mg/kg干物质。     

Amino acid availability from animal, blended, and plant feedstuffs for hybrid striped bass (Morone chrysops × M. saxatilis)

The refinement of hybrid striped bass feed formulations has been progressing rapidly. There is still, however, limited information available regarding nutrient digestibility and amino acid availability from common feedstuffs. A pair of experiments was conducted to determine the protein digestibility and amino acid availability to sunshine bass from an assortment of commercially available animal protein feedstuffs, blended animal products and plant protein feedstuffs in extruded diets. The feedstuffs tested were blood meal, poultry by‐product meal, fish solubles, Pro‐Pak 60, Pro‐Pak 65, ProCon 65RDB, and 60FMC for the animal protein feedstuffs and brewer's yeast, canola meal, peanut meal, and sunflower meal for the plant protein feedstuffs. Test diets consisted of a mixture of nutritionally complete reference diet and test ingredient. Triplicate tanks of fish were fed their respective diets for 7 days prior to collection of faeces by stripping. Apparent digestibility coefficients of protein (ADC‐CP) in the animal products ranged from 47% for 60FMC to a high of 70% for fish solubles. ADC‐CPs for animal products were not different across products. Blood meal, poultry by‐product meal, Pro‐Pak 60, Pro‐Pak 65, and ProCon had intermediate ADC‐CPs of 63, 55, 63, 57 and 52%, respectively. ADC‐CP in plant feedstuffs ranged from 43% for canola meal to 80% for peanut meal. Brewer's yeast, canola meal, and sunflower meal had intermediate ADC‐CPs at 54, 43 and 69%, respectively. Apparent amino acid availability coefficients were variable across animal products and did not necessarily correlate to the ADC‐CPs for a given feedstuff. Isoleucine availability was low in blood meal at 38% compared with 59% or better for the remaining amino acids. Lysine, tyrosine and phenylalanine availability from fish solubles was low at 31, 35 and 44%, respectively. Amino acid availability from Pro‐Pak 60 was consistently higher across all amino acids for the animal products and blends tested. Of the plant products tested, peanut meal was the best performing feedstuff relative to amino acid availability.     

Quantitative genetics and heritability of growth-related traits in hybrid striped bass (Morone chrysops ♀ × Morone saxatilis ♂)

Commercially farmed, hybrid striped bass - female white bass (Morone chrysops) crossed with male striped bass (Morone saxatilis) - represent a rapidly growing industry in the United States. Expanded production of hybrid striped bass, however, is limited because of uncontrolled variation in performance of fish derived from undomesticated broodstock. A 10 × 10 factorial mating design was employed to examine genetic effects and heritability of growth-related traits based on dam half-sib and sire half-sib families. A total of 881 offspring were raised in a common environment and body weight and length were recorded at three different times post-fertilization; parentage of each fish was inferred from genotypes at 10 nuclear-encoded microsatellites. Dam and sire effects on juvenile growth (weight and length) and growth rate were significant, whereas dam by sire interaction effect was not. The dam and sire components of variance for weight and length (at age) and growth rate were estimated using a Restricted Maximum Likelihood algorithm. Estimates of broad-sense heritability of weight, using a family-mean basis, ranged from 0.67 ± 0.17 to 0.85 ± 0.07 for dams; estimates for sires ranged from 0.43 ± 0.20 to 0.77 ± 0.10. Estimates of broad-sense heritability of growth rate (based on weight), using a family-mean basis, ranged from 0.69 ± 0.12 to 0.82 ± 0.09 for dams and from 0.69 ± 0.13 to 0.81 ± 0.08 for sires. Similar results were obtained with length data. Both genetic and phenotypic correlations between weight and length were close to unity. High genetic (0.98-0.99) and phenotypic (0.79) correlations between growth rates measured at two time intervals suggested that selection for growth rate at an early life stage could affect growth rate at a later life stage. Estimates of general combining ability (GCA) for growth rates differed significantly among dams and among sires, whereas estimates of specific combining ability (SCA) for each dam × sire combination did not differ significantly from zero. These results suggest that additive-effect genes contributed to the differences in juvenile growth.     

Selenium nutrition of hybrid striped bass (Morone chrysops × M. saxatilis) bioavailability, toxicity and interaction with vitamin E

Two concurrent 12-week feeding trials were conducted to evaluate the bioavailability of inorganic sodium selenite and organic seleno-DL-methionine and to investigate the potential interaction between selenium and vitamin E in juvenile hybrid striped bass. In experiment 1, purified diets utilizing casein, gelatin and an amino acid premix as protein sources with a basal selenium concentration of 0.11 mg Se   kg⁻¹ were supplemented with either Na₂SeO₃ to provide selenium concentrations of 1.19, 2.00, 5.17 and 21.23 mg Se kg⁻¹ or with seleno-DL-methionine to provide 0.90, 1.26 and 2.55 mg Se kg⁻¹ and fed to juvenile hybrid striped bass in aquaria. A second experiment evaluated potential interactions by feeding these purified diets with or without supplemental vitamin E or sodium selenite, singularly or in combination. No overt selenium deficiency signs were exhibited by fish in either of the experiments; however, signs of selenium toxicity including retarded weight gain (WG), reduced feed intake and feed efficiency ratio (FER) as well as increased mortality, were observed in fish fed the diet containing more than 20 mg Se kg⁻¹. Whole-body selenium and whole-body selenium retention were linearly influenced by sodium selenite and selenomethionine. However, there was no significant effect of dietary selenium, vitamin E or their interaction on WG, FER and survival. Slope-ratio analysis showed that bioavailability of seleno-DL-methionine as a selenium source for juvenile hybrid striped bass was significantly ( P  < 0.01) higher (3.3-fold) than sodium selenite.     

杂交条纹鲈苗种培育及成鱼养殖技术

杂交条纹鲈目前有两种 ,一种为六十年代中期在美国南加州生产的“原始杂交”种即用条纹狼鲈的卵与金眼狼鲈的精子人工杂交而得 ,另一种为雌性的金眼狼鲈与雄性的条纹狼鲈杂交种“阳光鲈”。条纹鲈和杂交条纹鲈为目前美国的主要养殖鱼类之一 ,主要用于游钓业及餐饮业。杂交条纹鲈因其具有显著的杂交优势 :生长速度快、个体大、抗病力强并具有集群摄食习性 ,易驯化饲养、起捕率高 ,且肉质白嫩、无肌间刺、营养价值高等特点 ,目前己成为淡水养殖的优良品种。我国台湾、沿海省份及内陆地区都已相继引进了杂交条纹鲈。根据我省近年来养殖该鱼的经…     

Survival of juvenile striped bass (Morone saxatilis) and Morone hybrid bass (Morone chrysops × Morone saxatilis) increased by addition of calcium to soft water

CaCl₂ was used to increase the total hardness of water in three ponds from 20 to 45–100 mg/l as CaCO₃ 5 days before harvest. CaCl₂ was also used to increase hardness from 10 to 70–200 mg/l as CaCO₃ in water used for holding and transporting fish after they were harvested from ponds. All groups of fish in water containing additional calcium had 80–99% survival compared with 16% survival for a group of fish without additional calcium in the water before or after harvest. Addition of 1% NaCl to the water did not increase survival.     

Dietary cholesterol and lecithin have limited effects on growth and body composition of hybrid striped bass (Morone chrysops × M. saxatilis)

The effects of cholesterol and lecithin on growth and body composition of juvenile hybrid striped bass ( Morone chrysops  ×  M. saxatilis ) were investigated by feeding juvenile hybrids (initial weight 5.0 g) diets containing cholesterol at either 0 or 1% and lecithin at either 0, 2, 4, or 6% in a 2 × 4 factorial design. Each of the eight diets was fed to fish in triplicate 38-L aquaria maintained as a brackish water recirculating system for 8 weeks. Weight gain, feed efficiency, muscle ratio and hepatosomatic index were not significantly ( P  > 0.05) affected by dietary supplementation of cholesterol or lecithin. Supplementation of the diet with lecithin at 4 and 6% significantly ( P  < 0.05) decreased intraperitoneal fat accumulation regardless of dietary cholesterol level. Neither muscle nor liver lipid levels were significantly altered by dietary supplementation of cholesterol or lecithin although both liver and plasma lipid classes were affected. Dietary cholesterol decreased concentrations of liver and plasma free fatty acids and liver phospholipids while increasing concentrations of liver triglycerides and plasma phospholipids. Dietary lecithin did not consistently affect plasma and liver lipid classes although changes in phospholipid levels approaching significance ( P =0.0502 and P =0.0513, respectively) were observed. Thus it is concluded that dietary supplementation with cholesterol or lecithin had no substantial beneficial effects on growth or body composition of juvenile hybrid striped bass.     

Selective breeding for the hybrid striped bass (Morone chrysops, Rafinesque ×M. saxatilis, Walbaum) industry: status and perspectives

The hybrid striped bass (HSB) farming industry has considerable potential for growth into domestic retail markets, but expansion of this industry is limited by high production costs that dictate high prices for HSB. It is widely recognized within the industry that selective breeding of an improved HSB will be required to increase production efficiency and reduce market prices. A National Program of Genetic Improvement and Selective Breeding for the HSB Industry has been initiated and some progress has been made toward domestication of the parent species of the hybrid. However, uncertainty remains as to which breeding procedures will most rapidly yield sustainable genetic gains in key production traits. This paper consolidates and reviews general information on the biology of temperate basses (genus Morone) relevant to selective breeding of improved HSB. The topics covered include control of reproduction, geographic distribution of stocks and population genetic variation. This is followed by a brief review of the current application of selective breeding techniques, including those based on molecular markers. Finally, we discuss potential avenues for genetic improvement of HSB in a selective breeding program.     

军曹鱼幼鱼对吡哆醇的需要量

以初始体重(3.23±0.06)g的军曹鱼为研究对象,以酪蛋白(不含维生素)、明胶、鱼肉浓缩蛋白为蛋白源,在基础饲料中分别添加0、2、4、8、16和32mgPN/kg,配制出6种实验饲料,使饲料中吡哆醇的水平分别达到0.22、1.89、3.87、7.54、14.75和29.88mgPN/kg,研究军曹鱼对吡哆醇的需要量。养殖实验在室内流水系统中(250L)进行,每个处理设3个重复,每个重复放养军曹鱼25尾。养殖实验过程中,海水盐度为30～34,水温28～32℃,溶氧>7mg/L,养殖实验持续9周。实验结果显示,在0.22～3.87mgPN/kg水平范围内,随着饲料中吡哆醇含量的升高,实验鱼特定生长率显著升高,当饲料吡哆醇水平达到或高于3.87mg/kg时,各饲料组实验鱼的特定生长率(2.68～2.71%/d)无显著差异,而都显著高于0.22和1.89mg/kg饲料组的特定生长率(1.17～2.06%/d)P<0.05)。军曹鱼肝脏吡哆醇含量、吡哆醛含量、谷丙转氨酶活力、谷草转氨酶活力均与特定生长率有相似的变化趋势,即在3.87mg/kg饲料组接近或者达到最大值,在达到或超过3.87mg/kg时达到或近似达到一...     

Immunomodulatory effects of β‐glucans derived from Euglena gracilis or Saccharomyces cerevisiae for hybrid striped bass (Morone chrysops × M. saxatilis)

Beta‐glucans (BGs) can activate the animal's innate immune system, enhancing the primary defence lines against pathogenic insults. The objective of this study was to assess the immune responses of hybrid striped bass (HSB) when exposed to paramylon, derived from Euglena gracilis, or zymosan, derived from Saccharomyces cerevisiae. Two separate trials were conducted to evaluate the efficacy of these immunostimulants as a feed additive or injected intraperitoneally. Five diets were formulated to contain either paramylon or zymosan at two different levels (50 or 100 mg/kg), and no supplementation serving as the control. Blood and head kidney were sampled, and an elevated production of anion superoxide from isolated phagocytes was observed for all supplemented groups when compared to the control. Dietary paramylon at 50 mg/kg increased immunoglobulin levels in the plasma. The second trial was conducted by injecting a BG solution (10 mg of β‐glucan kg^‐1 of body weight) and phosphate buffer solution serving as the control. Seven days after injection, blood samples were collected and immunological profiles from whole blood and plasma were significantly (p < .05) affected by the treatments. The results from this study indicate that both dietary and injected paramylon and zymosan modulated the immunological responses of HSB.