生态基挂设密度对草鱼生长性能和血清酶活性的影响

试验按生态基表面积占水泥池水体表面积比值(比表面积),设置50%(S-50)、100%(S-100)、150%(S-150)和对照组(无生态基)四个试验组,研究生态基挂设密度对草鱼生长性能和血清酶活性的影响。结果显示,S-100和S-150处理组草鱼的末重、增重率及特定生长率无显著差异,但均显著高于对照组和S-50组,饲料转化率均显著低于对照组,S-100处理组存活率显著高于其它处理组。S-100组水体COD含量显著低于对照组的,附着生物量(VSS)显著高于其它处理组。S-100与S-150组的过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均无显著差异,但均显著低于对照组和S-50组。试验组谷草转氨酶活性(AST)显著低于对照组。结果表明,生态基挂设密度影响草鱼的生长及其血清酶活性,挂设密度过高抑制微生物的附着生长,但超过100%的生态基挂设密度在一定程度上可能促进草鱼机体内的活性氧自由基代谢平衡,增强机体的抗氧化能力,促进草鱼生长。在本试验条件下,当挂设生态基的表面积占池塘水体表面积比值(比表面积)100%时,不仅可显著促进草鱼生长,提高养殖产量,降低饵料系数,而且能有效减少生态基使用量,进而降低生产成本。     

rpoS对鳗弧菌MHK3株Hcp表达和杀菌能力的影响

溶血素共调节蛋白(Hcp)的合成和分泌是六型分泌系统(T6SS)行使功能的重要特征。RNA聚合酶的σ亚基RpoS参与调节细菌的生长和应激反应。为了探究RpoS对鳗弧菌(Vibrio anguillarum) T6SS的调控作用,本研究构建了MHK3?rpoS突变株,检测了部分表型特征的变化;利用lacZ半乳糖苷酶报告基因检测了突变株hcp1和hcp2在转录水平的变化;进行Western blot并定量分析突变株Hcp在翻译水平的变化;并通过细菌拮抗实验检测了突变株杀菌能力的变化。结果显示,MHK3?rpoS突变株的生长情况、泳动性、明胶酶活性及酪蛋白酶活性与MHK3野生株相比无显著差异(P>0.05),而平台早期的菌膜形成能力有显著上升(P<0.05);在各生长时期,MHK3?rpoS的hcp1和hcp2在转录水平的表达量均较MHK3有显著上升(P<0.01),最高时分别为MHK3的1.79倍和1.94倍;在翻译水平上,MHK3?rpoS在胞内和胞外Hcp的分泌均有显著升高(P<0.05),最高时分别为MHK3的1.59倍和1.31倍;同时,MHK3?rpoS对大肠杆菌(Escherichia coli) E5的杀菌能力约为MHK3的1%。研究表明,rpoS对鳗弧菌MHK3株的生长情况、泳动性、明胶酶活性及酪蛋白酶活性均无显著调控作用,但对平台早期的菌膜形成能力具有一定的负调控作用,在转录和翻译水平上也负调控Hcp的表达。而在杀菌能力上,rpoS发挥一定的正调控作用。说明菌株的杀菌能力强弱并非直接与Hcp的表达和分泌量正相关。本研究为进一步阐明T6SS的调控机制及其介导的杀菌作用机制提供了新思路,并丰富了其理论基础。     

The effect of light on activity and growth of Atlantic halibut, Hippoglossus hippoglossus L., yolk-sac larvae

The growth and activity of Atlantic halibut, Hippoglossus hippoglossus L., yolk-sac larvae exposed to light of differing intensities and wavelengths were investigated every fifth day. The experiments were conducted at 6 ^oC from day 1 until day 34 post hatch. Four intensities of constant white light (2.0, 0.3, 0.03 and 0.005 μ Em^?2 s^?1, λ_max 590 nm), and constant coloured light of equal intensities (0.03μ Em^?2s^?1) in the blue, green and red spectrums (λ_max 450, 560 and 670 nm, respectively) were used. In addition to a control treatment in constant darkness, one treatment was incubated in a 12:12 h light: dark photoperiod. The light treatments did not have any discernible effect on the total length, myotome height, dry weights or yolk conversion efficiencies. The most intense white light resulted in an increased activity on days 24 and 30 post hatch, resulting in a temporarily reduced length and myotome height for the larvae in these groups compared to the other treatments. Larvae from all treatments were of the same size 34 days post hatch. The dry weights of the larvae and yolk-sacs were unaffected by light treatment. The activity increased independently of light treatment until 120 degree-days, and thereafter, the strongest white light resulted in an temporarily increased activity. The distribution of activity changed independently of light regime in the beakers during development.     

The effect of photoperiod on growth, survival, colour and activity of juvenile southern rock lobster, Jasus edwardsii

Juvenile (1–10 g) southern rock lobsters, Jasus edwardsii, were subjected to five photoperiods [0L(light):24D(dark); 6L:18D; 12L:12D; 18L:6D; 24L:0D] during a 112‐day trial, and growth, survival, colour, food consumption and activity were examined. Lobsters grown under the 6L:18D and 24L:0D photoperiods had significantly lower (P < 0.05) final mean weight and specific growth rate than any other treatments. Photoperiod had no effect on survival or colour of lobsters. Food consumption differed significantly during the first week of the trial; after 5 weeks, food consumption was similar in all treatments. Major peaks in activity occurred during dark periods for lobsters exposed to photoperiods that had a light:dark regime. Activity of lobsters exposed to continuous light or dark regimes remained constant and at low levels during the 24‐h period. Food consumption or activity does not appear to determine the rate of growth of lobsters in the different photoregimes. One over‐riding outcome of this and other studies on photoperiod is that the growth and survival response of juvenile J. edwardsii was not significantly better than those of the standard 12L:12D cycle.     

The effect of 2-phenoxyethanol and transport packing density on the post-transport survival rate and metabolic activity in the goldfish, Carassius auratus

To test the hypothesis that the anaesthetic 2-phenoxyethanol would reduce the metabolic rate and allow for higher transport packing densities, goldfish (3.93 +/- 5 g) were transported for 48 h at 25, 50 and 75 fish per 500 ml combined with anaesthetic concentrations of 0, 0.25 and 0.35 ml l-1. The anaesthetic did not affect the survival rate or the oxygen and ammonia concentrations. Thus, its use could not be recommended for the transport of goldfish. It is suggested that optimum packing densities be based on a minimum post-transport oxygen value of 4 mg l-1 for goldfish     

The effect of protein levels on growth,postprandial excretion and tryptic activity of juvenile mullet Mugil platanus (Günther)

The objective of the present work was to determine the optimum dietary protein level for juvenile mullets. Five isocaloric diets were formulated to contain increasing levels (300, 350, 400, 450 and 500 g kg^?1) of crude protein (CP) corresponding to 18.7 MJ metabolizable energy kg^?1. All diets were tested in triplicate. Each experimental unit was composed of a 50 L tank with 50 juveniles (mean ± SE initial weight and length equal to 1.17 ± 0.02 g and 4.34 ± 0.03 cm respectively). Diets were offered five times a day until apparent satiation for 35 days. No significant difference (P>0.05) was observed in survival rate, feed efficiency and body composition between treatments. However, weight gain, feed consumption and specific growth rate were higher in fish fed the 350 g kg^?1 CP level than those fed the highest protein content diet (500 g kg^?1 CP). The amount of postprandial ammonia excreted by mullet was linearly related to protein intake. Intestinal tryptic activity was inversely proportional to the percentage of dietary CP. It is likely that diets containing <350 g kg^?1 CP will be needed for on‐growing mullet, especially when reared in ponds with abundant natural food.     

The effect of migration distance and timing on metabolic enzyme activity in an anadromous clupeid, the American shad (Alosa sapidissima)

The American shad (Alosa sapidissima) is a common anadromous fish species with ecological and economic importance on the east coast of North America. This iteroparous species undergoes an energetically costly upriver spawning migration in spring. To evaluate metabolic changes associated with this migration, we assessed the maximum activity of five metabolic enzymes (citrate synthase (CS), phosphofructokinase (PFK), lactate dehydrogenase (LDH), -hydroxyacyl coenzyme A dehydrogenase (HOAD), alanine aminotransferase (GPT)) in liver, red muscle and white muscle during upstream migration in two successive years in the Connecticut River. For aerobic capacity (CS), glycolytic capacity (LDH) and utilization of stored lipid and protein energy (HOAD and GPT), there is a general pattern of increasing activity with a subsequent decline at the most upriver sites. Red muscle CS activity increased by as much as 40% during the migration while white muscle CS activity was 120% higher in the river than in the ocean. In contrast, muscle anaerobic capacity, indicated by PFK, was low as fish entered the river and then increased 5-fold at the most upriver sites. White muscle HOAD increased 30% while red muscle HOAD and muscle GPT increased as much as 60%. There were interannual and sex-associated differences in enzyme activity during upstream migration and through time at a single location. In some cases interannual differences can be larger than those seen during upriver migration as in the case of red muscle CS where sampling years differed by 125%. These interannual differences may be a result of differing river conditions that affect migratory effort. We have demonstrated that American shad use tissue and sex-specific regulation of enzyme activity during migration and we suggest that American shad metabolically acclimate to upstream migration.     

The effect of beta-glucan administration on macrophage respiratory burst activity and Atlantic salmon, Salmo salar L., challenged with amoebic gill disease--evidence of inherent resistance

Previous studies have demonstrated that beta-glucans stimulate Atlantic salmon, Salmo salar L., head kidney macrophages both in vitro and in vivo and increase protection against various pathogens. Based on our previous work that showed potent immunostimulatory CpG motif-containing oligodeoxynucleotides increased resistance to amoebic gill disease (AGD), the present study investigated the immunostimulatory effects of three commercial beta-glucan-containing feeds and their ability to increase resistance to AGD. All three commercial beta-glucans were able to stimulate the respiratory burst activity of Atlantic salmon head kidney macrophages in vitro, albeit at different times and concentrations. However, dietary incorporation of the beta-glucans was unable to stimulate the in vivo respiratory burst activity of head kidney macrophages, or serum lysozyme production, and did not increase resistance against AGD. However, this trial showed for the first time that a small subpopulation of Atlantic salmon subjected to a severe AGD infection was able to resist becoming heavily infected and furthermore survive the challenge.     

The effect of dietary energy level on growth and nutrient utilization by juvenile diploid and triploid brook charr,Salvelinus fontinalis

Triploids are used in aquaculture because they are sterile and do not undergo preharvest loss in flesh quality. Despite this advantage, they do not always perform as well as diploids when fed commercial diets. This study investigated whether differences in dietary energy utilization might explain this reduced performance. Dietary lipid levels were adjusted to supply diets with 22.7, 23.6 or 24.4 MJ kg^?1 gross energy and fed to juvenile diploid and triploid brook charr. Fish were fed to satiation twice daily in a 70‐day growth trial, with samples collected at days 0 and 70 for proximate composition and plasma insulin‐like growth factor I (IGF‐I) analysis. This was followed by a digestibility trial using the same diets to determine apparent digestibility coefficients. Triploids had lower growth rates and condition factor than diploids on all three diets, but there was no effect of ploidy on feed conversion efficiency. Triploids also had lower whole‐body lipid content, but equal protein content, which resulted in lower energy content at both days 0 and 70. There was no effect of diet or ploidy on plasma IGF‐I concentrations. Triploidy did not affect diet digestibility, suggesting that the reduced performance of triploids is due to a difference in metabolism and energy utilization.     

The effect of dietary protein replacement by crystalline amino acid on growth and nitrogen utilization of turbot Scophthalmus maximus juveniles

A study was conducted to evaluate the effect of partial replacement of dietary fish meal by crystalline amino acids on growth performance, feed utilization, body composition and nitrogen utilization of turbot juveniles.

Four diets were formulated to be isolipidic (12% DM) and isonitrogenous (8% DM). A fish meal based diet was used as control. In the experimental diets, a crystalline amino acid (AA) mixture was used to partially replace fish meal, corresponding to a non-protein nitrogen content of 19, 37 and 56%, respectively (diets 19AA, 37AA and 56AA, respectively). The overall amino acid profile of the experimental diets resembled that of the whole-body protein of turbot. Each experimental diet was fed to triplicate groups of 20 fish (initial body weight of 31.8 g) twice daily to apparent satiation for 42 days. During the trial water temperature averaged 18 °C.

Final body weight, weight gain (g kg ABW^− 1 day^− 1) and specific growth rate were not different between the control and 19AA diet but significantly decreased with the increase of crystalline-AA inclusion from 19 to 56%. Feed intake and feed efficiency of fish fed the control and diet 19AA were similar and significantly higher than those of fish fed the 56AA diet. At the end of the growth trial, there were no significant differences in whole-body composition among groups. Hepatosomatic index was also unaffected by dietary treatments.

Nitrogen retention (g kg ABW^− 1 day^− 1) of fish fed the control and the 19AA diets were similar and significantly higher than that of fish fed the other diets. Expressed as a percentage of the nitrogen intake, N retention was significantly higher with the control than with the 37AA and 56AA diets.

Daily ammonia excretion (mg kg ABW^− 1 day^− 1) of fish fed the control diet was significantly higher than that of fish fed the 37AA and 56AA diets, while daily urea excretion (mg kg ABW^− 1 day^− 1) did not significantly differ among treatments. Non-fecal nitrogen (ammonia + urea) excretion (mg kg ABW^− 1 day^− 1) was significantly higher for fish fed the control diet than in those fed the 37AA and 56AA diets. However, as percent of N intake, ammonia excretion and non-fecal N excretion were significantly higher in fish fed the 56AA diet than in those fed the control and 19AA diets.

Specific activity of glutamate dehydrogenase, alanine and aspartate aminotransferases did not significantly differ among experimental groups.

In conclusion, in diets with an overall amino acid profile resembling that of the whole-body protein of turbot, crystalline-AA may replace 19% of dietary protein without negatively affecting growth performances or feed utilization efficiency. However, higher protein replacement levels of protein-bound-AA by crystalline-AA severely depressed growth performance.     

The effect of lactic acid bacteria administration on growth,digestive enzyme activity and gut microbiota in Persian sturgeon (Acipenser persicus) and beluga (Huso huso) fry

The aims of this study was to assess the effect of two lactic acid bacteria (LAB), Lactobacillus curvatus and Leuconostoc mesenteroides, originally isolated from gastrointestinal (GI) tract of beluga (Huso huso) and Persian sturgeon (Acipenser persicus), respectively, on growth, survival and digestive enzyme (amylase, lipase and protease) activities and the population level of LAB in the GI tract. The treatments included 10 different groups; control, separate supplements of L. curvatus and Leu. mesenteroides at three different counts [2 × 10⁹, 5 × 10⁹ and 9 × 10⁹ colony forming units (CFU) per gram food] and three combinations of the two LAB (2 × 10⁹ + 2 × 10⁹, 5 × 10⁹ + 5 × 10⁹ and 9 × 10⁹ + 9 × 10⁹ CFU per gram food). The bacteria used in this study were added in lyophilized form to chopped Chironomidae. In the beluga study, highest specific growth rate, survival and improved intestinal enzyme activities were noted in the rearing group fed 9 × 10⁹ L. curvatus per gram food. In Persian sturgeon, the inclusion level of 2 × 10⁹ Leu. mesenteroides had similar positive effect. The ability of LAB to colonize the digestive tract seems to involve host specificity, and our bacteriological results are relevant to initiate future probiotic studies in sturgeons and future directions will be discussed.     

The effect of replacement of fish meal by yeast extract on the digestibility,growth and muscle composition of the shrimp Litopenaeus vannamei

Feeding trials were conducted to determine the dietary level of yeast extract (YE) for replacing dietary fish meal for evaluating whether yeast extract was superior to intact yeast as an alternative protein source for shrimp Litopenaeus vannamei. The basal diet (control, D0, containing 25% fish meal), was compared with five isonitrogenous and isoenergetic experimental diets [replacing 15% (D15), 30% (D30), 45% (D45), 60% (D60) or 100% (D100) of the fish meal in the basal diet with IYE]. The digestibility, growth and muscle composition of the shrimp were measured. The results showed that all replacement treatments displayed higher apparent digestibility of crude protein than did the control. The trypsinase activity in shrimp hepatopancreas increased significantly, whereas lipase activity decreased as the amount of dietary YE increased. The shrimp treated with D30 diet displayed the highest amylase activity in hepatopancreas. There was no significant difference in the weight gain (WG) and survival of shrimp between the control and the YE replacement treatments. Feed conversion ratio (FCR) increased as the dietary YE increased, and the FCRs of the D60 and the D100 treatments were significantly higher than that of the control (P < 0.05). The growth performance among the treatments was closely related to the similarity of the essential amino acids in the diets. There was no significant difference in muscle composition of the shrimp between control and other treatments. In conclusion, up to approximately 45% of the fish meal in shrimp diet can be replaced by yeast extract in the presence of supplemental fish oil, phosphorus and calcium.     

The effect of exogenously administered recombinant bovine somatotropin on intestinal phytase activity and in vivo phytate hydrolysis in hybrid striped bass Morone chrysops × M. saxatilis

It has been recently demonstrated that hybrid striped bass Morone chrysops × M. saxatilis exhibit intestinal phytase activity, an enzyme capable of liberating inorganic orthophosphate from the phytate molecule, thereby making phytate phosphorus (PP) available for absorption and utilization by the fish. However, it was also determined that hybrid bass were able to digest only 1–2% of dietary PP. Therefore, an experiment was conducted to determine if exogenously administered recombinant bovine somatotropin (rbST) would increase intestinal phytase activity in hybrid striped bass to a level that would improve PP availability. The results indicate that exogenous rbST treatment, administered either through intraperitoneal injection or orally, does increase intestinal brush border membrane protein concentration. While injection with rbST led to significant increases in both specific brush border membrane and total intestinal phytase activity, oral rbST administration did not cause similar increases. Total P and PP digestibility were not influenced by rbST administration. While treatment with rbST does have the potential to enhance intestinal phytase activity in hybrid striped bass, it does not appear to increase PP digestibility. This observation limits the hormone's utility as an effective technique for improving PP bioavailability to this species.     

The effect of ultrafiltered fish protein hydrolysate levels on the liver and muscle metabolic profile of juvenile turbot (Scophthalmus maximus L.) by 1H NMR‐based metabolomics studies

A ¹H NMR‐based metabolomics approach was to explore the effect of ultrafiltered fish protein hydrolysate (UF) levels on the liver and muscle metabolic profile of juvenile turbot (Scophthalmus maximus L.). Fish protein hydrolysate (FPH) was produced from by‐products by enzymatic treatment, and UF was obtained by diluting FPH followed filtration. Fish were fed diets containing fish meal protein, which was, respectively, replaced by UF protein 0, 50, 100, 150 and 200 g kg^?1 of dietary total protein (UF‐0, UF‐5, UF‐10, UF‐15 and UF‐20) for 68 days. OPLS‐DA of liver and muscle showed that high levels of UF in diets may lead to corresponding tissue metabolites changes. In liver tissue, changing metabolites included dimethylamine, N,N‐dimethylglycine, valine, isoleucine, leucine, arginine and alanine and were mainly involved in choline metabolism and amino acid metabolism. For muscle tissue, changing metabolites included lactate, alanine, proline, fumarate, tyrosine, histidine, cystathionine and taurine. And the metabolites were mainly involved in glycolysis and gluconeogenesis, proline metabolism and taurine metabolism. ¹H NMR‐based metabolomics is a useful approach to investigate different levels of UF on metabolic profile in liver and muscle tissues combined with the growth.