Effects of fasting on the meat quality and antioxidant defenses of market-size farmed large yellow croaker (Pseudosciaena crocea)

The study was conducted to investigate fasting effect on flesh composition and antioxidant defenses of market-size large yellow croaker (Pseudosciaena crocea). Two hundred fish (main initial weight 380 g) were divided into two groups (control and fasted) and reared in 6 cages. After two weeks of adaptation, group I fasted for 28 days; group II was fed normally as a control. In 3, 7, 14, 21 and 28 days, 6 fish per group were processed for proximate flesh composition, liver antioxidant enzyme activities and malondialdehyden flesh content analyses. In fasted fish, the reduction of lipid content in muscle occurred after day 3, and, compared to controls, the content of protein decreased from day 21, the activities of liver antioxidative enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPX) increased from day 3, and flesh malondialdehyde (MDA) levels increased from day 21. Muscle lipid reduction shows that the fasting technique is effective in end product improvement of large yellow croaker. However, considering flesh protein loss and the subsequent oxidative stress, the fasting technique should be used with precautions.     

网箱养殖大黄鱼溃疡病的预报模型

本文以舟山市网箱养殖大黄鱼Pseudosciaena crocea (Richardson)为研究对象,根据对2001-2005年间网箱养殖大黄鱼发病情况的观察分析、养殖水域环境因子的监测及其收集的气象资料,对大黄鱼溃疡病的发生规律和养殖环境的状况进行了全面分析,结果表明大黄鱼溃疡病的发生不仅与季节有关,而且还与环境因子的状况密切相关。在此基础上,进一步研究了环境因子对大黄鱼溃疡病发生的影响程度和影响方式,筛选出与大黄鱼溃疡病发生密切相关的环境因子,从而建立了网箱养殖大黄鱼溃疡病发生的预报模型。经检验该模型对预报大黄鱼的溃疡病是否发生及发生的程度有高度显著的效果,用该模型对舟山市2005年大黄鱼溃疡病的发生情况进行了预报,预报的正确率达到81.2%。为能有效、适时地对发病季节大黄鱼疾病的控制,本文还同时给出了网箱养殖大黄鱼发病季节溃疡病的预报模型。     

大黄鱼HPLC指纹图谱的建立及其在产地溯源和物种鉴别中的应用

通过优化实验条件,选择真空冷冻干燥的方法处理实验原材料,以乙酸乙酯为溶剂采用超声法(功率为250 W、提取时间2 h)制备原材料中的有效成分。运用Agilent 1260DAD-HPLC,采用Thermo ODS-C_(18)色谱柱,利用乙腈–0.1%磷酸水作为流动相,在流速0.5 m L/min、进样量20μL、210 nm条件下,建立了舟山养殖大黄鱼、福建养殖大黄鱼、小黄鱼、黄姑鱼和黑鳃梅童鱼的HPLC指纹图谱,以及具有18个共有峰的指纹图谱共有模式。相似度分析表明,其他几类样品和舟山大黄鱼的相似度排序为福建养殖大黄鱼小黄鱼黄姑鱼黑鳃梅童鱼。应用SPSS18.0数据分析软件,对18个共有峰的相对峰面积进行聚类分析、主成分分析和判别分析。聚类分析结果表明,大黄鱼、小黄鱼、黑鳃梅童鱼和黄姑鱼各自聚为一类,可用于鉴别不同的鱼类。经主成分分析,共选取到3个主成分PC1、PC2和PC3,涵盖了HPLC图谱数据信息的80.36%。根据3个主成分的得分绘制散点图,5种样品各自归于一定的区域,实现了不同产地大黄鱼以及大黄鱼与其他鱼类的鉴别。在此基础上,选择对主成分贡献较大的色谱峰的峰面积建立了5种样品的判别方程式,交互验证的正确率高达98.4%,可用于鉴别不同产地的大黄鱼及相同产地的相近鱼种。因此,本实验的研究结果为HPLC指纹图谱技术应用于大黄鱼产地溯源提供了理论和数据支持。     

Optimal dietary lipid level for large yellow croaker (Pseudosciaena crocea) larvae

A 30‐day feeding experiment was conducted in blue tanks (70 × 50 × 60 cm, water volume 180 L) to determine the effects of dietary lipid levels on the survival, growth and body composition of large yellow croaker (Pseudosciaena crocea) larvae (12 days after hatchery, with initial average weight 1.93 ± 0.11 mg). Five practical microdiets, containing 83 g kg^?1 (Diet 1), 126 g kg^?1 (Diet 2), 164 g kg^?1 (Diet 3), 204 g kg^?1 (Diet 4) and 248 g kg^?1 lipid (Diet 5), were formulated. Live feeds (Artemia sinicia nauplii and live copepods) were used as the control diet (Diet 6). Each diet was randomly assigned to triplicate groups of tanks, and each tank was stocked with 3500 larvae. During the experiment, water temperature was maintained at 23(±1) °C, pH 8.0 (±0.2) and salinity 25 (±2) g L^?1. The results showed that dietary lipid significantly influenced the survival and growth of large yellow croaker larvae. Survival increased with the increase of dietary lipid from 83 to 164 g kg^?1, and then decreased. The survival of larvae fed the diet with 83 g kg^?1 lipid (16.1%) was significantly lower than that of larvae fed other diets. However, the survival in larvae fed the diet with 16.4 g kg^?1 lipid was the highest compared with other artificial microdiets. Specific growth rate (SGR) significantly increased with increasing dietary lipid level from 83 to 164 g kg^?1 (P < 0.05), and then decreased. The SGR in larvae fed the diet with 164 g kg^?1 lipid (10.0% per day) was comparable with 204 g kg^?1 lipid (9.6% per day), but were significantly higher than other microdiets (P < 0.05). On the basis of survival and SGR, the optimum dietary lipid level was estimated to be 172 and 177 g kg^?1 of diet using second‐order polynomial regression analysis respectively.     

Effects of dietary vitamin C on survival, growth, and immunity of large yellow croaker, Pseudosciaena crocea

An 8 weeks growth experiment was conducted to determine the effects of dietary vitamin C on the survival, growth, tissue ascorbic acid contents and immunity of large yellow croaker (Pseudosciaena crocea) with initial weight of 17.82 ± 0.68 g. Seven practical diets were formulated to contain 0.1, 12.2, 23.8, 47.6, 89.7, 188.5 and 489.0 mg ascorbic acid equivalent kg^− 1 diet, supplied as l-ascorbyl-2-polyphosphate (LAPP). Each diet was fed to triplicate groups of fish in seawater floating cages (1.5 × 1.5 × 2.0 m), and each cage was stocked with 120 fish. Fish were fed twice daily (05:00 and 17:00) to apparent satiation for 8 weeks. The water temperature fluctuated from 19.5 to 25.5 °C, the salinity from 25 to 28‰ and dissolved oxygen content was approximately 7 mg l^− 1 during the experimental period. Results showed that the specific growth rate (SGR) (from 1.80 to 1.96% d^− 1) had an increasing trend with the increase of dietary vitamin C, but no significant difference was observed among dietary treatments. No gross deficiency signs were observed in any of the experimental fish. Survival rate, however, significantly increased with increasing dietary vitamin C (P < 0.05). The vitamin C contents in liver and muscle correlated positively with the vitamin C in diets. The vitamin C requirement was estimated to be 28.2 mg kg^− 1 based on survival, and 87.0 mg kg^− 1 on liver content of vitamin C. The activities of serum lysozyme and alternative complement pathway (ACP), phagocytosis percentage (PP) and respiratory burst activity of head kidney significantly increased with increasing dietary vitamin C. The challenge experiment with Vibrio harveyi showed that fish fed the diets with supplementation of vitamin C had significantly lower cumulative mortality compared to the control group (66.7%), and the cumulative mortality (16.7%) in fish with 489.0 mg kg^− 1 ascorbic acid was significantly lower than that (41.7%) in fish with 23.8 mg kg^− 1 ascorbic acid. These results suggested that vitamin C significantly influenced the immune response and disease resistance of large yellow croaker.     

Replacement of fish meal by meat and bone meal in practical diets for the white shrimp Litopenaeus vannamai (Boone)

The use of meat and bone meal (MBM) was evaluated as a replacement for fish meal in a practical diet formulated to contain 41% protein and 8% lipid. Anchovy meal was replaced by 0%, 20%, 30%, 40%, 50%, 60% and 80% of MBM (diets 1–7) respectively. Healthy post larvae of Litopenaeus vannamei were reared in an indoor, semi‐closed recirculating system. Each dietary treatment was fed to triplicate groups of 40 shrimp per tank (260 L) arranged in a completely randomized design. The shrimp were hand‐fed to near‐satiation three times daily between 07:00 and 18:00 hours for 56 days. There were no significant differences (P>0.05) in growth performance among shrimp fed diets 1–6. However, shrimp fed diet 7 had significantly lower (P<0.05) growth than those fed diet 2 or diet 4. Survival ranged from 95% to 100% and did not significantly (P>0.05) differ. Feed conversion ratio (FCR) and carcass composition of the shrimp were not significantly (P>0.05) affected by dietary treatments. No significant differences (P>0.05) in protein efficiency ratio (PER) were found among shrimp fed diets 1‐6. However, shrimp fed diet 7 had significantly lower (P<0.05) PER than those fed diet 1 or diet 4. Results showed that up to 60% of fish meal protein can be replaced by MBM with no adverse effects on growth, survival, FCR, PER and body composition of L. vannamei.     

大黄鱼幼鱼对饲料中锌需要量

以初始体重为(1.78±0.02)g的大黄鱼为实验对象,在室内流水系统(养殖桶规格:200L)中进行为期8周的摄食生长实验,研究大黄鱼对饲料中锌的需要量.通过在基础饲料中添加ZnSO4·H2O使饲料中锌含量分别达到9.68、30.63、48.94、91.28、167.49和326.81mg·kg-1.每种饲料设3个重复,每个重复放养40尾大黄鱼.实验采取饱食投喂方式,每天投喂2次(05:30和17:30),实验期间水温为26.5～29.5℃,盐度为25～28,溶解氧含量在7mg·L-1左右.实验结果表明各饲料处理组成活率(84.2%～96.7%)无显著差异.随着饲料中锌含量的增加,大黄鱼的特定生长率(SGR)显著升高[(2.47～2.77)%·d-1,P<0.05],且在91.28mg·kg-1锌饲料组达最大值(2.77%·d-1),然而,随着饲料中锌含量的进一步增加,SGR维持在一相对稳定水平,各处理组间体蛋白(14.0%～15.0%),体脂肪(5.4%～6.1%),灰分(3.7%～4.1%)及水分含量(76.1%～77.9%)均无显著差异(P0.05).饲料锌含量显著影响大黄鱼脊椎骨、全鱼和血清中锌的含量,而对肝脏锌含量无显著影响.以SGR与骨骼锌含量为评价指标,根据折线模型得出大黄鱼对饲料中锌的需要量分别为59.6和84.6mg·kg-1.     

运输密度和盐度对大黄鱼幼鱼皮质醇、糖元及乳酸含量的影响

为了确定大黄鱼运输的适宜条件,实验选取平均体质量为(0.12±0.03)g的大黄鱼幼鱼为实验对象,采取析因设计,设3个运输密度(2、4和8 g/L)和5个运输盐度(5、10、15、20和25),共计15个处理组研究了不同密度和盐度运输条件下,大黄鱼幼鱼皮质醇、糖元及乳酸含量的变化。经过水温16.5℃、10 h的运输,统计各组的死亡率,测定各组水中总氨氮含量。结果显示,在运输结束后,4和8 g/L密度组死亡率(1.33%、2.63%)显著高于2 g/L密度组(0.77%),盐度25组死亡率(0.44%)显著低于盐度10、15组(1.94%、1.67%),盐度10、15组死亡率显著低于盐度5组(2.72%),各组水中总氨氮含量较运输前(0.15 mg/L)均显著升高,各密度组水中总氨氮含量均有显著性差异,高密度组总氨氮含量高于低密度组,8 g/L密度条件下盐度5组水中总氨氮含量(1.63 mg/L)显著高于盐度15(1.38 mg/L)、盐度20(1.34 mg/L)和盐度25(1.31 mg/L)组,4 g/L密度条件下盐度5组水中总氨氮含量(1.31mg/L)显著高于其他各盐度组,2 g/L密度条件下盐度5组水中总氨氮含量(0.83 mg/L)显著高于盐度25组(0.49 mg/L);运输胁迫导致各组皮质醇含量均较运输前(6 476.35 ng/L)显著升高,各组间皮质醇含量无显著性差异;各组糖元含量均较运输前(4.37 mg/g prot)显著降低,运输后各组间糖元含量无显著性差异;各组乳酸含量均较运输前(0.57 mmol/g prot)显著升高,运输后各密度组间乳酸含量无显著性差异,3个密度下盐度5组乳酸含量(1.91、2.02、1.76 mmol/g prot)均显著高于盐度20(1.55、1.21、1.69 mmol/g prot)和盐度25组(1.36、1.44、1.26 mmol/g prot),盐度10组乳酸含量(1.77、1.83、1.60 mmol/g prot)显著高于盐度25组(1.36、1.44、1.26 mmol/g prot)。研究表明,较高的运输密度和较低的盐度会加重大黄鱼的应激性反应,在本实验条件下,规格为0.1 g左右的大黄鱼幼鱼,其运输密度不宜超过8g/L,盐度不宜低于5。     

脂多糖对大黄鱼原代头肾巨噬细胞的激活作用

为了揭示硬骨鱼C型凝集素受体 (C-type lectin receptor,CTLR)的生物学功能,实验以从大黄鱼转录组数据库中筛选出的一个CTLR基因—C型凝集素结构域家族4成员E基因 (Clec4e)为研究对象,研究其分子特征、表达分布和凝集特性。结果显示,LcClec4e cDNA全长1 546 bp,开放阅读框 (ORF)771 bp,编码254个氨基酸。LcClec4e的N端有一个跨膜区,无信号肽,C端含有一个糖识别结构域 (CRD),其中含有糖结合位点EPN和WFD以及6个可形成二硫键的保守半胱氨酸。系统发育分析表明,LcClec4e与多种鲈形目鱼类Clec4e具有较近的亲缘关系。荧光定量PCR结果显示,LcClec4e在所检测的10种组织中呈组成型分布,且在肝脏中表达量最高;LcClec4e在来源于大黄鱼头肾组织的原代巨噬细胞、淋巴细胞和粒细胞中均有表达,且在巨噬细胞中表达量最高;经灭活溶藻弧菌刺激后,LcClec4e在3种免疫细胞中的表达均极显著上调。原核表达的重组LcClec4e胞外段 (recombinant LcClec4e-extracellular domain,rLcClec4e-ex)具有Ca²⁺依赖性的凝集活性,可凝集小鼠、家兔的红细胞,以及嗜水气单胞菌、变形假单胞菌、溶藻弧菌和坎氏弧菌等4种水产常见的革兰氏阴性菌。D-葡萄糖、D-果糖、D-甘露糖、D-麦芽糖、α-乳糖和脂多糖均可抑制rLcClec4e-ex对大黄鱼重要病原菌变形假单胞菌的凝集作用,说明LcClec4e可能与变形假单胞菌表面的糖类物质结合。上述结果提示,LcClec4e可能作为一种模式识别受体,通过结合病原菌表面的糖类病原体相关分子模式来识别病原,参与大黄鱼抗细菌感染的免疫防御。

     

大黄鱼肿瘤抑制因子cylindromatosis (LcCYLD)的序列与免疫反应特征及其功能

为研究大黄鱼肿瘤抑制因子cylindromatosis（CYLD）在免疫反应中的作用,本实验克隆了大黄鱼CYLD的全长cDNA（命名为LcCYLD）并对其进行序列分析;采用荧光定量PCR的方法对大黄鱼各组织及免疫刺激后的大黄鱼肾细胞系中的LcCY LD表达变化进行检测;构建了重组表达载体pTurboGFP-CYLD及pcDNA3.1-CYLD,分别用于亚细胞定位实验及过表达实验;在HEK293T细胞系中过表达LcCYLD后采用双荧光素酶报告系统检测了 NF-κB、TNF-α及IL-1β 启动子活性的变化。结果显示,LcCYLD的ORF包含2 754 bp,编码917个氨基酸,推测具有保守的3个N端的CAP-GLY结构域,1个磷酸化区域和1个C端的UCH结构域,多序列比对结果显示各物种CYLD间高度保守;系统进化分析显示,LcCYLD与来源于其他硬骨鱼的CYLD聚为一支,其中与条纹鲈的CYLD关系最近;转录水平表达分析发现LcCYLD在大黄鱼各组织均有表达,其中在脑中表达量最高;LPS及poly I:C刺激能够显著诱导LcCYLD的表达;亚细胞定位实验表明LcCYLD在细胞质及细胞核中均有表达;过表达LcCYLD能够显著抑制NF-κB及促炎细胞因子TNF-α及IL-1β的转录激活。以上研究结果表明大黄鱼CYLD能够抑制NF-κB的转录激活,为深入了解LcCYLD在大黄鱼先天免疫信号转导中的作用奠定基础。     

大豆浓缩蛋白替代鱼粉对大黄鱼幼鱼生长、体成分、血清生化指标及肝组织学的影响

为探索大豆浓缩蛋白(SPC)替代鱼粉水平对大黄鱼(Larimichthys crocea)幼鱼生长、体成分和血清生化指标以及肝组织学的影响。以初始体重为(10.50±0.04)g的大黄鱼幼鱼为研究对象,用SPC替代基础饲料(含40%鱼粉)0%(FM)、25%(R25)、50%(R50)、75%(R75)、100%(R100)的鱼粉制作成5种等氮(粗蛋白水平为45%)等脂(粗脂肪水平为10%)的实验饲料。各实验组以对照组(FM)饲料蛋氨酸、赖氨酸含量为基准,分别添加适量的晶体赖氨酸和蛋氨酸。养殖实验在浙江省象山县西沪港区进行,每个处理随机分配3个网箱(1.5 m×1.5 m×2 m),每个网箱放养60尾,养殖周期为56 d。结果表明,与对照组相比(FM),SPC替代鱼粉水平对大黄鱼幼鱼的增重率(WGR)、特定生长率(SGR)、存活率(SR)以及饲料系数(FCR)没有显著影响(P0.05);肌肉粗蛋白和全鱼粗蛋白无显著差异(P0.05),肌肉粗脂肪和全鱼粗脂肪含量随替代比例的增加有下降的趋势,均以R100组含量最低,肌肉水分含量和全鱼水分有上升的趋势;血清各项指标没有显著性差异,但血清总蛋白(TP)、白蛋白(ALB)含量有下降趋势,以R100组含量最低;血清胆固醇(CHOL)、甘油三酯(TG)的含量呈现出先升高后下降的趋势。从肝组织学观察中发现,SPC替代水平超过75%会对肝细胞产生损伤,引起肝细胞空泡化,脂肪堆积加重,肝细胞核逐渐溶解或缺失。综上所述,在本研究条件下,SPC替代饲料75%的鱼粉,不会对大黄鱼幼鱼的生长造成负面影响。     

大黄鱼同质雌核发育的诱导及微卫星标记分析

为了解大黄鱼同质雌核发育的诱导条件及其效果,用紫外线照射灭活大黄鱼精子的遗传物质,静水压休克抑制第一次卵裂,培育出2个同质雌核发育家系(GF1和GF2),并借助微卫星标记进行鉴定,研究了10个母本中杂合的位点在2个家系中的传递和分离。结果显示,GF1和GF2孵出的仔鱼中分别有40.0%和17.1%形态正常个体,GF1检测8个位点30个个体均表现出雌核发育双单倍体（GDH）的特征,有20种基因型;GF2检测4个位点30个个体中,27个为GDH,2个含有父本基因,余下1个个体扩增条带既不同于母本也不同于父本,遗传本质不明。可见,所采用方法可以诱导出同质雌核发育大黄鱼。10个标记中除了LYC0026和LYC0053标记在GF2中偏离了1∶1（P<0.05）,其余标记在GDH中的分离均符合孟德尔遗传定律的预期比值。研究还发现LYC0002和LYC0014的分离模式完全相同。首次报道了大黄鱼同质雌核发育的人工诱导及微卫星标记在GDH中的传递与分离,为大黄鱼纯系培育及利用GDH与纯系进行基因组作图分析等研究奠定了基础。     

饲料中三种不同碳水化合物对大黄鱼生长性能和肝脏糖代谢关键酶活性的影响

为研究饲料中添加3种不同的碳水化合物对大黄鱼生长性能、饲料利用以及糖代谢关键酶活性的影响,进行为期8周的生长实验和持续24 h的饥饿实验。以葡萄糖、小麦淀粉和糊精这3种碳水化合物作为糖源,设计3组等氮等脂(48%粗蛋白和12%粗脂肪)的饲料。选用初始体质量为(8.51±0.02)g的大黄鱼450尾,随机分为3组(每组3个重复,每个重复50尾)。养殖实验结束后进行饥饿实验,分别在饥饿实验开始后的0、1、3、5、7、9、11和24 h取样。结果显示,小麦淀粉组和糊精组大黄鱼的增重率和特定生长率显著高于葡萄糖组,且这2个饲料组的饲料系数显著低于葡萄糖组。糊精组大黄鱼的肝体比显著高于其余2组大黄鱼的肝体比。饲料中添加3种不同碳水化合物对大黄鱼成活率、脏体比和肥满度无显著性影响。葡萄糖组和小麦淀粉组大黄鱼血糖含量在饥饿1 h后都开始显著上升,葡萄糖组高血糖水平持续至少10 h;小麦淀粉组3 h显著下降至初始水平左右,未达到高血糖水平;糊精组大黄鱼血糖含量随着时间的推移持续升高,在11 h达到最大值,高血糖水平持续4 h。饲料中添加3种不同碳水化合物对大黄鱼血清胰岛素和肝糖原含量有显著性影响。小麦淀粉对大黄鱼肝脏葡萄糖激酶(GK)活性的升高有诱导作用。大黄鱼摄食3种不同碳水化合物饲料后鱼体血糖水平升高,但糖异生关键酶如葡萄糖-6-磷酸酶(G6Pase)、果糖-1,6-二磷酸酶(FBPase)和磷酸烯醇式丙酮酸羧激酶(PEPCK)的活性并不降低。饲料中添加葡萄糖和小麦淀粉对大黄鱼肝脏丙酮酸激酶(PK)活性有显著性影响。研究表明,大黄鱼利用结构复杂的多糖(如小麦淀粉和糊精)的能力要高于单糖(如葡萄糖),3种不同碳水化合物对大黄鱼血糖调节及糖酵解和糖异生途径关键酶活性的影响存在差异。     

电解水预处理对冷藏大黄鱼品质变化的影响

为探究电解水预处理对冷藏大黄鱼品质变化的影响,实验利用有效氯浓度分别为50、100和200 mg/L的电解水和1%NaCl溶液浸泡处理新鲜大黄鱼,考察其在4°C冷藏过程中的菌落总数、挥发性盐基氮(TVB-N)值、ATP关联化合物含量、pH值、硬度、色泽、滋味和气味的变化。结果显示,伴随冷藏时间的延长,对照组鱼肉的菌落总数、TVB-N值、HxR含量、Hx含量、K值和pH值逐渐增加,而电解水处理抑制了这些品质指标的增加,抑制效果与有效氯浓度成正比。在同一冷藏时间下,鱼肉的黄度b*值随有效氯浓度的增加而增加。贮藏过程中,对照组鱼肉的苦味、苦味回味和丰富性逐渐增加,鲜味、咸味和甜味逐渐降低,而电解水处理组鱼肉的苦味回味和咸味均高于对照组。有效氯浓度为200mg/L的电解水预处理能减少鱼肉在冷藏4～10 d期间的挥发性气味,但在冷藏16 d后反而高于对照组。研究表明,电解水处理能有效延缓冷藏大黄鱼的品质变化,但当电解水的有效氯浓度较高时会导致鱼肉色泽变黄和腐败后的挥发性气味增加。研究结果为电解水在大黄鱼保鲜中的应用及其有效氯浓度的选择提供了理论参考。     

大黄鱼感染哈维氏弧菌后血液生化指标的变化及组织病理学观察

从患病大黄鱼病灶中分离出病原哈维氏弧菌,并人工回接感染大黄鱼,病鱼出现典型的皮肤溃疡症。测定大黄鱼血液各项指标发现,病鱼单核细胞、嗜中性粒细胞、血栓细胞百分率明显下降,而淋巴细胞百分率增加,均呈极显著差异(P<0.01)。患病大黄鱼总蛋白为(12.8±3.95)g/L,对照组鱼为(19.4±4.33)g/L,病鱼球蛋白、甘油三脂、血糖含量也明显低于对照组(P<0.01)。然而病鱼谷丙转氨酶为(37±5.11)IU/L,对照组为(28±5.54)IU/L;病鱼谷草转氨酶为(164±47.19)IU/L,对照组为(117±21.84)IU/L,均呈极显著差异(P<0.01)。研究结果说明,病鱼肝脏和肾脏组织受损。对患病大黄鱼进行病理组织学观察,结果发现病鱼病变组织头肾、肝出现不同程度的变性以及坏死。细胞超微病变观察发现,头肾肾小管上皮细胞变性、坏死。肝细胞胞浆内脂滴积累多。血清指标的测定可以作为大黄鱼哈维氏弧菌病细菌感染的指标。     

Dietary fishmeal levels affect the volatile compounds in cooked muscle of farmed large yellow croaker Larimichthys crocea

A comparative study on the volatile compounds in cooked muscle of wild and farmed large yellow croaker (LYC) was conducted. The two farmed LYC groups were fed with diets containing 44% (CF) and 25% (LF) of fish meal (FM) respectively. Results showed that 48 volatiles, including aldehydes, alcohols, ketones, hydrocarbons, aromatics, acids, esters, furans and miscellaneous compound, were detected in cooked fillets. The LF group had significantly lower amounts of total aldehydes and ketones, higher content of miscellaneous compound in cooked fillets than that in the CF and wild groups (p < .05). Compared with the wild group, the LF group had significantly lower amounts of total alcohols, acids and esters, while the CF group had significantly lower amounts of total aldehydes, higher content of total ketones in cooked muscle (p < .05). According to the principal component analysis (PCA), some volatiles (propanal, nonanal, etc.) could be considered as sensitive indicators to classify cooked muscle samples. In conclusion, differences in the volatiles in the cooked muscle between the wild and farmed LYC have been found. Low level of dietary FM (25%) changed the volatile profiles in cooked fillets of farmed LYC. A PCA may be useful to screen potential volatiles to classify cooked muscle samples in this study.     

Replacement of fish meal with poultry by-product meal in diets formulated for the humpback grouper, Cromileptes altivelis

An eight-week feeding trial was conducted to examine the possibility of replacing fish meal with poultry by-product meal (PBM) at high inclusion levels in the diets of the humpback grouper, Cromileptes altivelis, a carnivorous marine tropical fish. Six isolipidic (12%) and isoproteic (50%), experimental diets were formulated to contain graded levels of PBM. Fish meal protein was replaced with a feed-grade PBM at 50, 75 or 100% level (FPBM50, FPBM75, FPBM100, respectively), or a pet food grade PBM at 75 or 100% replacement level (PPBM75 and PPBM100, respectively). The control diet contained Danish fish meal as the sole protein source. The experimental diets were fed close to apparent satiation, twice a day to triplicate groups of humpback grouper fingerlings (12.4 ± 0.2 g). The grouper fingerlings were randomly distributed into groups of 15 fish in cylindrical cages (61 cm depth and 43 cm diameter) and placed in a 150-ton seawater polyethylene tank. Except for fish fed the FPBM100 diet, growth performance, survival, and feed utilization efficiency for fish fed PBM-based diets were not significantly lower (P > 0.05) compared to fish fed the control diet. The PBM source and dietary level did not significantly affect (P > 0.05) the hepato- and visero-somatic indices or the condition factor of fish. Dry matter and protein apparent digestibility coefficients (ADC) of the diets decreased with increasing dietary PBM, and ranged from 64.3-71.5% and 86.2 to 91.2%, respectively. High values (91.7 to 96.7%) for lipid ADC were observed in all diets, with no significant differences among dietary treatments. Whole-body moisture and lipid contents of the fish were not affected by the inclusion of PBM in the diets. With the exception of fish fed the FPBM100 diet, whole-body protein of fish fed the PBM-based diets was slightly higher than that of fish fed the control diet. There was a trend of increased whole-body ash with the increase in dietary levels of PBM. The results from this study indicate that good quality terrestrial PBM can successfully replace more than half the protein from marine fish meal in the diets for humpback grouper. However, total replacement of fish meal with PBM might be constrained by lowered nutrient digestibility and limiting essential amino acids, especially lysine and methionine.     

冷藏养殖大黄鱼细菌相组成和优势腐败菌鉴定

从菌落和细胞形态、生理生化特征、细胞脂肪酸组成及同源性分析等方面,结合使用Sensititre、BioFosun、MIDI细菌鉴定系统对0 ℃、5 ℃冷藏养殖大黄鱼货架期终点细菌相进行定性和定量研究,确定优势腐败菌。0 ℃、5 ℃冷藏优势菌为腐败希瓦氏菌,比例分别为75.5%、59.6%,在营养琼脂和胰酶解大豆胨琼脂培养基上菌落圆状隆起,边缘整齐,透明,无色至粉红色,革兰氏阴性杆菌,极生单鞭毛,大小为(0.6～0.9) μm×(1.5～3.3) μm,最适生长温度25～35 ℃、最适pH 7～9。菌株氧化酶和H2S呈阳性,能还原TMAO、液化明胶和Tween40,利用N乙酰基D葡萄糖胺等有机物。菌体主要脂肪酸为16∶1ω7c 、iso15∶0、17∶1ω8c、16∶0,比例分别为21.31 %、13.63%、9.82%、9.76%。菌株测试特征与细菌鉴定系统数据库比照,确定优势腐败菌为腐败希瓦氏菌。