三甲氧苄氨嘧啶对养殖大菱鲆盾纤毛虫病治疗效果的研究

从感染纤毛虫的养殖大菱鲆上分离获得盾纤毛虫进行体外培养,通过药物抑制实验发现,三甲氧苄氨嘧啶(TMP)对盾纤毛虫的最小有效抑制浓度为25×10~(-6);TMP对大菱鲆的毒性实验表明,24小时半致死量为每千克鱼体内含药物量为0.35357 g,48小时半致死量为每千克鱼体内含药物量为0.33912 g,安全量为每千克鱼体内含药物量为0.09361 g;TMP对大菱鲆盾纤毛虫病的治疗实验结果显示,与对照组相比,注射药物或投喂药饵后,感染纤毛虫的大菱鲆成活率提高了50%～107.1%。     

基于C-R模型比较大菱鲆快速生长品系和普通养殖群体的生长特征

大规模家系选育技术也称为现代育种技术,具有选择效率高、可抑制遗传衰退等优点,是进行分子辅助育种技术的基础。基于此,采用这项技术开展了大菱鲆快速生长性状遗传改良研究。为了系统评估大菱鲆快速生长选育的育种成效,运用C-R模型分别对选育出的大菱鲆快速生长品系和普通养殖群体的非线性生长曲线进行了拟合和比较分析,深入揭示选育出的大菱鲆快速生长品系和普通养殖群体的生长差异。研究结果显示,快速生长品系和普通养殖群体C-R模型的拟合度、拐点月龄、拐点体质量、最大月增体质量分别为0.999和0.997、15.228和16.858月龄、716.712和619.862 g、111.711和78.061 g;快速生长品系的瞬时生长率、瞬时生长加速率、相对生长率分别在4.5~25月龄、3~13.8月龄、3~15月龄,高于普通养殖群体,在其他相应阶段,快速生长品系的瞬时生长率和瞬时生长加速率低于普通养殖群体,而相对生长率无显著差异;快速生长品系的始速点、拐点和终速点均比普通养殖群体提前,并且快速生长期时间区间长度(12.35月龄)小于普通养殖群体(15.28月龄),其对应的体质量区间长度(1 187.680 g)大于普通养殖群体(1 027.120 g),即基于家系选育技术获得的大菱鲆快速生长品系在较短的快速生长时间区间范围内,获得了更大的净增体质量,取得了更大的遗传进展。     

The differences in postprandial free amino acid concentrations and the gene expression of PepT1 and amino acid transporters after fishmeal partial replacement by meat and bone meal in juvenile turbot (Scophthalmus maximus L.)

Meat and bone meal (MBM) is a high‐quality alternative protein source used to replace fishmeal (FM). However, the molecular mechanisms of over‐substituted FM by MBM resulted in growth reduction are still not clear. The objective of the study was to evaluate the effect of FM replacement by MBM on the concentration of postprandial free amino acid (FAA) and mRNA abundance of peptide and amino acid transporters in juvenile turbot (Scophthalmus maximus L.). Fish were fed with FM diet (60% FM), MBM diet (33% FM + 34.2% MBM) and MBM + AA diet (MBM diet with essential amino acid (EAA) added to match the AA profile of FM) for 30 days. Results showed that compared with the FM diet, MBM diet led to a reduction in FAA concentration peak values in plasma and muscle. MBM + AA diet significantly elevated the peak values of FAA concentrations to FM diet level in plasma, but not in muscle. Furthermore, compared with FM diet, MBM diet significantly increased gene expression of PepT1 and major amino acid transporters in intestine, whereas MBM diet greatly downregulated gene expression of T‐type amino acid transporter‐1, system ASC amino acid transporter‐2 and cationic amino acid transporter‐2 in muscle. Supplemented EAA did not ameliorate these different effects in intestine and muscle. Overall, this study provided a comprehensive explanation for the relationship between diet, FAA concentrations and AA transportations, which provides a molecular basis for further using MBM to replace FM in aquafeeds.     

鸡抗迟缓爱德华氏菌卵黄抗体的应用研究

从全身出血合并腹水的养殖大菱鲆Scophthalmus maximus体内分离出1株细菌,经感染试验证实其病原性,并鉴定该菌为迟缓爱德华氏菌Edwardsiella tarda。采用该菌制成全菌油乳性灭活疫苗,分4次给蛋鸡进行免疫注射,第2次加强免疫后开始收集鸡蛋,制备卵黄抗体(IgY)和其水溶性组分(W SF),并用试管凝集法测定其效价。取效价达到1∶64的鸡蛋提取卵黄抗体,分别采用口服和腹腔注射两种方式给大菱鲆进行免疫:配成含W SF 1 mL/g的饵料,给鱼连续投喂15 d;用含蛋白含量0.19 mg/mL的纯化IgY,于第1、3、14 d对大菱鲆进行腹腔注射,剂量为0.1 mL尾/。免疫后分别用注射和划伤浸泡两种方法攻毒。结果表明,口服特异性卵黄抗体对大菱鲆的免疫保护率分别为83.3%和100%,而注射免疫没有保护作用。     

混合微藻替代鱼油对大菱鲆幼鱼生长性能、体组成及肠道部分生化指标的影响

本实验以大菱鲆(Scophthalmus maximus)幼鱼[(39.69±0.25) g]为研究对象,探究由裂壶藻(Schizochytrium sp.)和拟微绿球藻(Nannochloropsis sp.)组成的混合微藻替代鱼油对幼鱼生长性能、体组成、肠道消化水平及抗氧化能力的影响,以确定混合微藻替代鱼油的适宜比例。通过在基础饲料中添加不同比例的混合微藻,分别替代0、25%、50%和100%的鱼油,制成4组等氮等脂的实验饲料(分别命名为D1、D2、D3和D4),每组饲料设3个重复,实验周期为12周。结果显示,随替代比例的提高,大菱鲆幼鱼的增重率(WGR)和饲料效率(FE)呈下降趋势,D1、D2和D3组的特定生长率(SGR)和FE无显著性差异,但均显著高于D4组(P<0.05);肝体比(HSI)在D1组达到最大值,且显著高于其他各组(P<0.05);存活率(SR)和肥满度(CF)在各组之间无显著差异(P>0.05)。随着混合微藻替代鱼油比例的升高,全鱼和肌肉粗脂肪含量呈先升高后降低的变化趋势,且D4组显著低于D1组(P<0.05);大菱鲆幼鱼鱼体中C20:4n-6和n-6 PUFA含量显著升高,在D4组均达到最大值,且显著高于对照组(P<0.05)。而EPA、DHA和n-3 PUFA含量随之显著下降,对照组(D1)含量显著高于其他各组(P<0.05);肌肉中C20:4n-6和DHA含量在不同实验组间无显著性差异(P>0.05),EPA和n-3 PUFA含量呈显著降低趋势(P<0.05)。肠道脂肪酶活力在D3组达到最大值,显著高于对照组(P<0.05),肠道胰蛋白酶活力也是在D3组最高,但与对照组无显著性差异(P>0.05)。与D1组相比,D3组肠道中酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、溶菌酶(LZM)活力和补体C3含量均显著升高(P<0.05)。肠道中超氧化物歧化酶(SOD)、总抗氧化能力(T-AOC)和过氧化氢酶(CAT)活力随替代比例的提高呈先升高后降低的趋势,均在D3组达到最大值,显著高于D1组(P<0.05),而肠道中丙二醛(MDA)含量在不同实验组间并未表现出显著性差异(P>0.05)。综上所述,混合微藻替代50%的鱼油并不会对大菱鲆幼鱼的生长性能产生负面影响,同时可以提高肠道的消化性能、抗氧化能力和非特异性免疫能力。     

大菱鲆幼鱼的蛋白质与能量需求

饲料中蛋白质的含量对大菱鲆幼鱼的生长起着决定性作用，适宜的能蛋比，既有利于能量的利用，又有利于蛋白质的利用，提高了饲料的利用率。设计4个蛋白质含量梯度和4个能量梯度的16组饲料，试验证明，蛋白质含量大于42％、能蛋比小于115，鱼体日增重率明显增大，饲料系数明显降低，表现出较高的饲料效率，本研究认为大菱鲆幼鱼配合饲料适宜的蛋白质含量为42％～45％、适宜的能蛋比为92．7～102．5。     

Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot (Scophthalmus maximus L) reared under optimum salinity and temperature conditions

Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot was determined at optimum salinity and temperature conditions of 17 g L^?1 and 19.2 °C, respectively, by using 3 × 2 (protein levels: 550, 600 and 650 g kg^?1; lipid levels: 69 and 168 g kg^?1) factorial design with three replications of each. Fish were hand‐fed to satiety twice daily throughout the feeding trial. Weight gain and specific growth rate of fish were significantly (P < 0.05) increased with increased dietary lipid level, but not by dietary protein level. Daily feed intake was significantly (P < 0.05) affected by both dietary protein and lipid levels. Feed efficiency ratio and protein efficiency ratio were significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Moisture content of whole body was significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Crude lipid content of whole body was significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Significantly higher 20:5n?3, 22:6n?3 and n?3 highly unsaturated fatty acids were observed in turbot fed the low lipid diet than fish fed the high lipid diet in all protein levels, but significantly lower 18:2n?6 was observed in fish fed the former compared with the latter. In considering results of growth, specific growth rate and efficiency of feed, optimum dietary protein and lipid levels for juvenile turbot seemed to be 550 and 168 g kg^?1 of the diet, respectively, under optimum salinity and temperature conditions.     

Nursery growth, survival and chemical composition of great scallop Pecten maximus (L.) spat from different larval settlement groups

Scallop Pecten maximus spat (1.3–2.1 mm shell height) from different settlement groups were transferred from hatchery to land‐based nursery at different ages and sizes. Chemical content, growth and survival were compared at transfer time and after 1 and 8 weeks of nursery growth. Growth was lowest and mortality highest in the first week after transfer. Mean shell height growth was 21.5–71.4 μm day^?1 and ash‐free dry weight (AFDW) growth ?2.7 to 10.3 μg day^?1. Spat from the first settlement group attained a larger size and weight than spat from larvae settled 3 days later, but had a lower daily growth rate (%). Keeping the late‐settled spat a longer time in the hatchery to reach a bigger size before transfer seemed not to improve subsequent nursery growth. Survival showed a large variation with mean survival ranging from 32% to 74%. A substantial reduction in lipid content was found after transfer to the nursery. Sterol content at transfer was the only lipid class correlating with survival in the nursery. Based on the results, it is justified that spat groups of different settlement age are included in production of 15‐mm great scallop spat if they are transferred from the hatchery at the same age.     

Effect of a dietary phospholipid supplementation on growth and fatty acid composition of European sea bass (Dicentrarchus labrax L.) and turbot (Scophthalmus maximus L.) juveniles from weaning onwards

Two 40-day feeding trials using extruded diets were conducted to assess the effect of a dietary phospholipid (PL) supplementation on growth, survival and fatty acid composition of European sea bass (Dicentrarchus labrax) and turbot (Scophthalmus maximus) from weaning onwards. Two dietary treatments (FO and PL) were tested; both had an identical extruded basis (92.5% total diet weight) coated with a different lipid fraction (7.5% total diet weight). Diet PL contained 2% egg yolk PL (69% pure). In diet FO the PL was replaced by hydrogenated coconut oil. The isolipidic diets contained an equal amount of fish oil ethyl esters providing 1.6% (% diet dry weight) of n-3 highly unsaturated fatty acids (HUFA). A diet water stability test showed no effect of the PL supplementation on the leaching of the dietary fatty acids. In both fish species weight, but not survival, significantly increased as a result of PL supplementation. Weaning onto the experimental diets resulted in similar changes in the relative percent levels of fatty acids in both species. In general, the percentage of saturated fatty acids levelled off after a rapid increase, while monoenes increased after an initial decrease. Total n-3 polyunsaturated fatty acids (PUFA) decreased and total n-6 PUFA remained almost constant. The major effect of the dietary PL on fish fatty acid composition was a 50% increase in n-6 and n-3 HUFAs compared to the PL-free FO diet. The rise in n-6 HUFA may have reflected the higher moiety in the dietary PL. On the other hand this was not the case for the n-3 HUFA since they represented only low levels in the PL fraction (0.1%) compared to that provided by the ethyl esters (1.6%) suggesting a more efficient incorporation of the PL n-3 HUFA than of the ethyl ester n-3 HUFA. A second hypothesis is that the dietary PL may have favored the incorporation of the dietary ethyl ester n-3 HUFA.     

Comparison of mortality of wild and released reared 0-group turbot, Scophthalmus maximus, on an exposed beach (Ría de Vigo, NW Spain) and a study of the population dynamics and ecology of the natural population

Abstract  Marked reared turbot, Scophthalmus maximus (L.) (594) were released onto an exposed beach nursery ground together with marked wild fish (438) of approximately the same size (4–6 cm TL) and were sampled at intervals for 38 days. A consistent ratio of marked wild: unmarked wild indicated that marking did not increase mortality. The wild 0-group turbot population size was estimated at 1540 at the time of release, indicating that hatchery-reared individuals could theoretically make a significant contribution to the local population size. However, the absolute and relative catches of the marked, reared fish were lower than those of the marked wild fish, and no reared fish were caught after 23 days. The higher mortality rate was attributed to both a smaller size and their hatchery-reared origin. The population dynamics of the 1994–1995 year-classes of wild turbot were also studied. Recruitment of post-larvae (3 cm) to the beach started in March and continued until October. Population size peaked over the August–October period. Juvenile turbot remained on the nursery beach until June of the following year when they presumably emigrated to deeper water. During this 15-month period their length increased from 3 to 12–15 cm.