酵母免疫多糖对受免斑点叉尾免疫应答的增强作用

在饲料中添加定量的酵母免疫多糖,投喂注射接种了福尔马林灭活的嗜水气单胞菌(Aeromonas hydrophila)菌苗的斑点叉尾(Ictalurus punctatus),28 d后通过测定供试鱼的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性(SGPT)、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了酵母免疫多糖对受免斑点叉尾免疫应答的增强作用。结果表明,用添加200.0 mg/(kg.d)酵母免疫多糖的饲料投喂受免斑点叉尾,不仅可以使受免斑点叉尾对灭活嗜水气单胞菌的免疫应答水平提高,增强抵抗嗜水气单胞菌人工感染的能力,而且还具有一定的促进生长和改善肝功能的作用。     

斑点叉尾病毒病研究概述

简要介绍了斑点叉尾病毒病的临床症状、流行病学特征、诊断与防治方法以及病毒的生物学特性与检测技术等。     

HACCP体系在斑点叉尾人工繁殖中的应用

在江西峡江和赣州进行了HACCP(Hazard Analysis and Critical Control Point)体系在斑点叉尾(Ictaluruspunctatus)人工繁殖中的应用研究。应用HACCP的基本原理,对整个斑点叉尾人工繁殖过程进行危害分析,确立了亲鱼培育池的选择、亲鱼种质选择、亲鱼产卵池的选择、受精卵孵化、苗种培育、水质监测、饲料供应、日常管理等8个关键控制点,提出了相应的预防措施、关键限值、监控措施以及超过关键限值时的纠正措施,使各关键控制点处于人为控制之下。实现了斑点叉尾人工繁殖按无公害化、规范化、标准化生产。     

酵母免疫多糖对受免斑点叉尾鲴免疫应答的增强作用

在饲料中添加定量的酵母免疫多糖，投喂注射接种了福尔马林灭活的嗜水气单胞菌（Aeromonas hydrophila）菌苗的斑点叉尾鲴（Ictalurus punctatus），28d后通过测定供试鱼的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性（SGPT）、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率（RPS），探讨了酵母免疫多糖对受免斑点又尾鲴免疫应答的增强作用。结果表明，用添加200．0mg／（kg·d）酵母免疫多糖的饲料投喂受免斑点叉尾鲴，不仅可以使受免斑点叉尾鲴对灭活嗜水气单胞菌的免疫应答水平提高，增强抵抗嗜水气单胞菌人工感染的能力，而且还具有一定的促进生长和改善肝功能的作用。     

酵母免疫多糖对受免斑点叉尾(鮰)免疫应答的增强作用

在饲料中添加定量的酵母免疫多糖,投喂注射接种了福尔马林灭活的嗜水气单胞菌(Aeromonas hydrophila)菌苗的斑点叉尾(鮰)(Ictalurus punctatus),28 d后通过测定供试鱼的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性(SGPT)、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了酵母免疫多糖对受免斑点叉尾(鮰) 免疫应答的增强作用.结果表明,用添加200.0 mg/(kg·d)酵母免疫多糖的饲料投喂受免斑点叉尾(鮰),不仅可以使受免斑点叉尾(鮰) 对灭活嗜水气单胞菌的免疫应答水平提高,增强抵抗嗜水气单胞菌人工感染的能力,而且还具有一定的促进生长和改善肝功能的作用.     

斑点叉尾胃肠道嗜银细胞的分布密度及形态学观察

用改良的龙桂开浸银法对斑点叉尾(Ictalurus punctatus)胃肠道嗜银细胞的总数及形态学特征进行了观察。结果显示嗜银细胞在胃至肠道各段均有分布,分布密度呈波浪形,即胃体部最高,中肠其次,胃幽门部最低。嗜银细胞在胃贲门部和中肠常成群分布,大多数嗜银细胞呈棒状、梭形、三角形和蝌蚪形等,胃部和后肠中偶见呈圆形的细胞。对结果进行分析表明,斑点叉尾胃肠道嗜银细胞主要行使外分泌功能,其数目和形态特征可能与其食性、消化特性有关。     

斑点叉尾致病性嗜水气单胞菌的分离

从贵州乌江库区某渔场发病的斑点叉尾中分离出4株细菌。经形态学、染色特性、溶血性和生理生化特性鉴定,分离到3株嗜水气单胞菌。实验接种到鲤和小白鼠分别于48h和72h全部死亡,并从实验鲤鱼和小白鼠中回收到分离菌。药敏试验表明,它们对常用抗生素呈不同程度的敏感性。     

一株斑点叉尾致病菌的分离鉴定

从斑点叉尾(Ictalurus punctatus)肝脏分离到的一株细菌GD091027,对该菌进行人工感染试验、生理生化特性测定和16S rRNA序列测定并构建系统发育树,同时进行了抗菌药物敏感性试验。结果显示:当人工感染剂量大于1.0×107 CFU/尾时,能引起斑点叉尾100%发病死亡,对斑点叉尾的LD50为6.2×104 CFU/g。分离株GD091027为革兰氏阴性短杆菌,氧化酶阴性,在25℃、35℃均有运动性,能耐3%的NaCl,不发酵葡萄糖、麦芽糖、蔗糖、D-甘露醇及L-阿拉伯糖,不利用西蒙氏柠檬酸盐,不利用丙二酸,赖氨酸脱羧酶和鸟氨酸脱羧酶阳性,产生硫化氢和吲哚,甲基红(MR)试验阴性。在16S rRNA系统发育树中,该菌与迟缓爱德华氏菌(Edwardsiella tarda)聚为一分支。分离株GD091027对氨苄西林、庆大霉素、妥布霉素等16种抗菌药物敏感,利福平、青霉素等3种抗菌药物不敏感。除不产生溶血、不发酵葡萄糖和麦芽糖、甲基红(MR)试验阴性外,病原菌形态及生理生化特征符合迟缓爱德华氏菌,结合16S rRNA序列分析结果将其鉴定为迟缓爱德华氏菌。     

斑点叉尾鮰致病性嗜水气单胞菌的分离

从贵州乌江库区某渔场发病的斑点又尾鲴中分离出4株细菌。经形态学、染色特性、溶血性和生理生化特性鉴定，分离到3株嗜水气单胞菌。实验接种到鲤和小白鼠分别于48h和72h全部死亡，并从实验鲤鱼和小白鼠中回收到分离菌。药敏试验表明，它们对常用抗生素呈不同程度的敏感性。     

不同商品饲料对生长、体色及肝脏组织结构的影响

本试验评估了(Ictalurus punctatus)主产区4种商品颗粒饲料(分别记为S1、S2、S3和S4,其中S4为膨化饲料,其他均为颗粒饲料)和自行设计的颗粒饲料(记为S5)对试验阶段生长性能、体色变异、肝胰脏组织结构及形态指标的影响。7周的饲喂试验结果显示:饲料蛋白含量为38%的S4膨化饲料可明显的提高养殖鱼的体重,平均增重率为262.6%,但存活率较低,仅为72.3%;而喂养S5饲料组的增重率为168.89%,且存活率为92.4%,高于其他饲料组。养殖结束后,不同试验组的肥满度、脏体比有所差异,但均未达到显著性水平(P>0.05)。投喂S2饲料组养殖鱼体体色发白比较明显,体色异常比例高达91%;S4饲料组养殖后体色发白也比较明显,体色异常比例为72.3%;对背部黑色素扫描研究进一步证实饲喂S2饲料和S4饲料的黑色素细胞发生了变化,黑色素细胞边缘变得模糊,而自配S5饲料的黑色素细胞树突状分支较多;饲喂S4饲料组的背部斑点比例为12.15%,而S2饲料组的背部斑点比例为26.38%,自配S5饲料组的背部斑点比例为35.69%,S4饲料组的斑点比例明显较低。     

Re-evaluation of vitamin E supplementation of practical diets for channel catfish, Ictalurus punctatus, production

A 10-month feeding trial was performed with channel catfish, Ictalurus punctatus , to re-evaluate the minimum level of dietary vitamin E supplementation required under conditions of commercial production. Four levels (0, 15, 30 and 60 mg kg⁻¹ diet) of supplemental vitamin E were added as DL -α-tocopherol acetate to a typical commercial catfish diet. Sixteen 0.04-ha ponds were stocked in July, at a rate of 25 000 fish ha⁻¹, with two size classes (averaging 18 and 265 g fish⁻¹) of fingerling channel catfish, and each diet was fed to fish in four replicate ponds once daily to satiation. After 10 months of feeding, a total harvest was performed to obtain final production data, and samples were obtained from fish in all ponds. Liver and plasma samples were obtained for α-tocopherol determination, and liver, heart and muscle samples were processed for histological evaluation.
No discernible differences occurred among fish fed the different diets with respect to weight gain or survival. Mean production rate was 9734 kg ha⁻¹, with a final average fish weight of 0.53 kg. A significant ( P < 0.05) effect of diet was noted in plasma and liver α-tocopherol levels, which increased with dietary supplementation. An effect of size also was apparent, with plasma and liver α-tocopherol levels being higher in larger fish compared with smaller fish within a dietary treatment. Histological evaluation revealed no differences among fish fed the different dietary treatments. Based on the lack of overt histological signs of deficiency, it appears that the current level of vitamin E supplementation of commercial catfish diets may be reduced considerably with no detriment to channel catfish health or production.     

Edwardsiella ictaluri bacteraemia elicits shedding of Aeromonas hydrophila complex in latently infected channel catfish, Ictalurus punctatus (Rafinesque)

Edwardsiella ictaluri is a primary bacterial pathogen of channel catfish, Ictalurus punctatus, and the causative agent of enteric septicaemia of catfish . Edwardsiella ictaluri is known to gain entry to the host by infection of the nares, gastrointestinal tract, and gills, and to disseminate to organs via an as yet uncharacterized acute bacteraemia. In this study, fluorescent microscopy showed E. ictaluri on the gill within 5 min of immersion challenge and E. ictaluri could also be isolated from the circulation within 5 min. When removed to clean water, catfish cleared circulating bacteria within 15 min and the blood remained free of E. ictaluri until its reappearance at the 12 h post-infection sampling. However, Aeromonas hydrophila , the aetiological agent of motile aeromonad septicaemia, appeared within the circulation 7 h post-challenge with E. ictaluri and was detected in all fish at 12 h post-infection. Only 20% of fish carried A. hydrophila in the trunk kidney that could be detected by plate culture on Rimler–Shotts agar; however, 100% of challenged and stress-control fish were A. hydrophila complex positive at 24 h post-challenge. These results suggest that although the catfish is capable of clearing its circulation of E. ictaluri , superinfection with latent A. hydrophila may enhance clinical signs of edwardsiellosis. This is the first report of a bacterial superinfection appearing in fish.     

Dietary protein concentration and daily feed allowance influence response of channel catfish, Ictalurus punctatus (Rafinesque), to ractopamine

Year-1 channel catfish, Ictalurus punctatus (Rafinesque) (average initial weight, 48 g) were fed diets containing 240 g kg^?1, 300 g kg^?1, or 360 g kg^?1 dietary protein with 0 or 20 mg kg^?1 ractopamine to satiation and diets containing 240 g kg^?1 and 360 g kg^?1 protein with 0 or 20 mg kg^?1 ractopamine at a restricted rate (60% of satiation) in aquaria at 29 ± 2°C for 8 weeks. Fish fed ractopamine at the 360 g kg^?1 protein level gained significantly more weight than controls when fed to satiation but not when the ration was restricted. Fish fed ractopamine at the 240 g kg^?1 protein level did not gain more weight than the controls at satiation or restricted feeding. Fish fed ractopamine in the diet containing 300 g kg^?1 protein gained significantly more weight than controls when fed to satiation. Ractopamine caused no significant differences in feed conversion at the 240 g kg^?1 or 360 g kg^?1 protein levels with restricted or satiation feeding. Muscle fat decreased when ractopamine was fed at all dietary protein levels and at both feeding rates. Muscle protein increased with ractopamine feeding in all treatments except the high-protein, satiation treatment. Weight gain response of year-1 channel catfish to ractopamine is dependent upon nutrient concentration of the diet and ration size; however, the effect of ractopamine on muscle composition of channel catfish is less dependent on nutrient concentration or amount of diet fed.     

利用mtDNA控制区序列分析斑点叉尾(鮰)的遗传多样性

利用m tDNA控制区序列对1984、1997年引进的斑点叉尾鮰群体遗传多态性进行了分析。通过PCR产物测序法,测定了40尾斑点叉尾鮰线粒体DNA的一段包括部分Cytb基因、tRNAThr、tRNAPro、D-loop控制区和部分tRNAThe长度为1256 bp的核苷酸序列,经过比对分析得到7个序列单元型。7个单元型中共有13个碱基转换位点,全部发生在控制区,其序列相似度平均为99.58%。群体总的序列单元型多态性比例为17.5%,其中1997年群体的单元型多态性比例为35%,是1984年群体单元型多态性比例(15.0%)的2倍多。初步表明1984年引进的群体遗传多样性较低。     

外源核苷酸对斑点叉尾(鱼回)生长及肠道组织发育的影响

以斑点叉尾(鱼回)幼鱼为试验对象,研究不同水平外源核苷酸对其生长和肠道发育的影响.在基础饲料中分别添加0.0%(对照组)、0.02%、0.05%和0.1%的外源核苷酸.结果表明,在斑点叉尾(鱼回)幼鱼日粮中添加外源核苷酸,促生长作用不显著(P>0.05),但可显著促进肠道组织的发育(P<0.05).