急性氨氮胁迫对黄颡鱼组织抗氧化酶活性及HSP70和HSP90基因mRNA表达水平的影响

为了探讨急性氨氮胁迫对黄颡鱼组织中抗氧化酶活性及HSP70和HSP90基因mRNA表达水平的影响,实验随机挑选了360尾黄颡鱼[初体质量(17.25±0.05)g],分别暴露于含有0(对照)、5.70(低浓度组)、28.50(中浓度组)和57.00(高浓度组)mg/L总氨氮浓度的水体中,进行96 h的急性胁迫实验。实验开始后,分别于0、12、24、48和96 h取样。结果显示,氨氮胁迫发生后,低、中浓度组实验鱼肝脏中超氧化物歧化酶(SOD)活性呈先升高后降低趋势,而高浓度组则持续降低;低、中、高浓度组实验鱼肝脏中丙二醛(MDA)含量在胁迫开始后显著升高;3 h时,高浓度组实验鱼肝脏中SOD活性达到最低,而MDA含量最高;24 h后,高浓度组实验鱼肝脏中过氧化氢酶(CAT)活性显著升高;低、中、高浓度组实验鱼肝脏中HSP70基因的mRNA表达量呈先降低后升高趋势,而鳃中HSP70基因表达量持续升高,但脑中HSP70基因在0 h后显著降低;氨氮胁迫3 h时,低、中、高浓度组实验鱼肝脏和脑中HSP70基因表达量显著低于对照组,而在鳃中正好相反;相比HSP70基因,高氨氮浓度组实验鱼肝脏和鳃中HSP90基因的mRNA表达量在24 h时达到最高。研究表明,不同浓度的氨氮胁迫会对黄颡鱼抗氧化酶活性造成不同程度的抑制,原因与丙二醛的积累量有关;相比HSP90基因,黄颡鱼HSP70基因的表达量在氨氮胁迫发生后迅速上调,这种生理调控机制提示HSP70在应对急性氨氮胁迫时发挥着更重要的作用。     

饲料中添加雨生红球藻对黄颡鱼生长、抗氧化酶活性、免疫应答及氨氮耐受的影响

为探讨饲料中添加雨生红球藻对黄颡鱼生长、抗氧化酶活性、免疫应答及氨氮耐受的影响。以平均体质量为（5.00±0.85）g的黄颡鱼为研究对象,随机分成4个组,每组3个重复,每个重复30尾鱼,分别投喂添加0.00 %（对照）、0.30 %、0.50 %及1.00 %雨生红球藻的饲料,每天2次表观饱食投喂,实验进行10周。结果显示,饲料中雨生红球藻的添加量大于0.30 %能够显著提高黄颡鱼的增重率和血红蛋白含量,降低饲料系数和白细胞数;饲料中添加0.50 %雨生红球藻能够显著降低黄颡鱼血清超氧化物歧化酶和谷胱甘肽过氧化物酶活性及丙二醛含量,显著提高血清溶菌酶活性;96 h急性氨氮暴露实验表明,摄食0.50 %-1.00 %雨生红球藻饲料的黄颡鱼累积死亡率和血氨含量显著低于对照组;饲料中添加雨生红球藻显著提高了氨氮暴露下黄颡鱼肝脏中氨代谢相关酶含量,其中,氨甲酰磷酸合成酶和精氨酸酶含量随着雨生红球藻含量的升高显著提高。研究表明,饲料中添加大于0.30 %雨生红球藻能够显著提高黄颡鱼的生长性能,改善血液健康状况、氧化损伤及免疫应答能力;饲料中雨生红球藻的添加量超过0.50 %能够显著提高黄颡鱼在氨氮暴露下的存活率。     

pH与氨氮对黄颡鱼幼鱼生长与肝脏超氧化物歧化酶的影响

为了解不同水体pH和氨氮组合对瓦氏黄颡鱼(Pelteobagrus vachelli)特定生长率(SGR),饲料效率(FE)和肝脏超氧化物歧化酶(SOD)活力的影响。实验采用中心复合设计与响应曲面法分析方法,利用瓦氏黄颡鱼幼鱼开展试验,养殖周期为7周。结果表明,水体氨氮对SGR,FE和肝脏SOD活力有显著影响;pH对SGR有显著影响。pH对SGR,FE和SOD活力存在显著的二次效应。氨氮浓度小于1.7 mg/L时对黄颡鱼生长无抑制作用;高氨氮与高pH环境对幼鱼的生长、饲料利用与肝脏SOD活力有明显的抑制作用。水体pH和氨氮水平分别为7.5和1 mg/L时,SGR、FE和SOD同时最优,分别为1.47%/d、1.71和97.9 U/(mg.prot),优化的可信度为0.836。建议在黄颡鱼养殖中,将pH与水体氨氮维持在7.0~8.0与0.1~1.7 mg/L内,从而保证黄颡鱼的正常生长与较强的抗氧化活性。     

急性氨氮毒性对黄颡鱼头肾巨噬细胞抗氧化及炎症相关基因表达的影响

为了研究急性氨氮胁迫对黄颡鱼头肾巨噬细胞抗氧化及炎症相关基因表达的影响，实验通过建立黄颡鱼离体头肾细胞模型，开展为期96 h的急性氨氮胁迫实验。结果显示，0.14和0.28 mg/L总氨氮处理组SOD基因的相对表达量显著低于对照组，但0.28 mg/L总氨氮处理组GPX基因的相对表达量显著高于其他组；0.14和0.28 mg/L总氨氮处理组IL-1和TNF基因的相对表达量显著低于对照组，而0.28 mg/L总氨氮处理组IL-8基因的相对表达量显著低于0.14 mg/L总氨氮处理组和对照组；吖啶橙染色检测发现，0.14 mg/L总氨氮处理组实验鱼头肾巨噬细胞内可见边缘不规则的黄绿色荧光，0.28 mg/L总氨氮处理组实验鱼头肾巨噬细胞内可见致密浓染的黄绿色荧光信号。研究表明，氨氮毒性能够影响黄颡鱼头肾巨噬细胞抗氧化相关基因的表达；细胞凋亡可能是造成鱼类氨中毒致死的主要原因之一。     

黄曲霉毒素B1对黄颡鱼幼鱼生长及肝脏功能的影响

为研究黄曲霉毒素B1(Aflatoxin B1, AFB1)对黄颡鱼幼鱼生长、肠道消化酶及肝脏功能的影响,用添加不同梯度黄曲霉毒素B1(AFB1)(0、50、100和200μg/kg)的4种等氮等脂配合饲料饲喂初始体质量为(6.00±0.10) g的黄颡鱼幼鱼8周。结果显示:(1)饲料中添加AFB1对黄颡鱼幼鱼的存活率、饲料系数和特定生长率等均无显著影响,但使胰蛋白酶活性显著提高,而高含量AFB1(100和200μg/kg)显著降低肠道淀粉酶和脂肪酶活性;(2)随着AFB1添加量的上升,血清中谷丙转氨酶、谷草转氨酶活性及葡萄糖、甘油三酯、总胆汁酸和总胆固醇含量显著升高,肝脏中谷丙转氨酶、谷草转氨酶活性显著下降;(3) AFB1添加组的肝脏过氧化氢酶活性和丙二醛含量显著高于对照组,100和200μg/kg AFB1组超氧化物歧化酶活性显著高于对照组,其余各组无显著差异;(4) AFB1添加组肝脏sod基因及炎性因子il-1β基因的相对表达量显著上调,200μg/kg AFB1组cat基因及炎性因子il-8、il-10相对表达量显著上调;(5)通过组织学观察,AFB1会引起部分肝细胞出现轻微萎缩、肝细胞核移位、细胞界限模糊和肝细胞内空泡化的现象。研究表明,在本实验条件下,饲料中AFB1含量低于200μg/kg不影响黄颡鱼幼鱼生长性能,但饲料中AFB1≥50μg/kg时会影响黄颡鱼幼鱼肠道的消化吸收功能,同时引起肝脏氧化应激及炎性反应,造成肝脏功能损伤。     

蟋蟀粉替代鱼粉对黄颡鱼幼鱼生长性能、肌肉氨基酸组成和血清生化指标的影响

为研究蟋蟀(Gryllus bimaculatus)粉替代鱼粉对黄颡鱼(Pelteobagrus fulvidraco)幼鱼生长性能、肌肉成分和血清生化指标的影响，以黄颡鱼幼鱼[(2.0±0.13) g]为研究对象，分别使用蟋蟀粉替代0 (对照组)、15%、30%、45%和60%的鱼粉配制成5组等氮等能的实验饲料，分别记为T0、T15、T30、T45和T60组。实验幼鱼在室内循环水系统进行为期10周的养殖实验。结果显示，随着蟋蟀粉替代量的增加，黄颡鱼幼鱼生长呈先增加后降低的趋势；T30组的终末均重(FBW)、增重率(WGR)和特定生长率(SGR)最高，且均显著高于T0组；T30组的饲料系数(FCR)显著低于T0和T15组；T30的肝体比(HSI)显著高于T0和T15，而与T45和T60组无显著差异。与T0组相比，各替代组的脏体比(VSI)、摄食量(FI)、肥满度(CF)和成活率(SR)均无显著差异。黄颡鱼幼鱼肌肉必需氨基酸(EAA)含量中，T60组肌肉中精氨酸(Arg)和缬氨酸(Val)含量显著高于T0组；且蟋蟀粉替代不同比例的鱼粉对黄颡鱼幼鱼肌肉中的总呈味氨基酸(TFAA)含量均未产生显著影响。T30、T45和T60组血清中的葡萄糖(GLU)含量显著高于T0组；相反，其总胆固醇(TCHO)含量显著低于T0组。在本研究条件下，蟋蟀粉替代不同比例的鱼粉不影响黄颡鱼幼鱼的生长性能和肌肉氨基酸含量，且能增加血清GLU和降低TCHO含量，以30%的蟋蟀粉替代鱼粉比例能生长最佳，且优于对照组。本研究对揭示蟋蟀粉在黄颡鱼饲料中替代鱼粉应用的可行性、为今后昆虫蛋白源在水产饲料中的开发提供科学依据。     

饲料中添加酵母培养物对黄颡鱼生长性能、非特异性免疫和肠道健康的影响

为研究饲料中添加酵母培养物对黄颡鱼生长性能、非特异性免疫和肠道健康的影响，在基础饲料中分别添加0、1%和2%的酵母培养物YC1(粗蛋白含量为50%)、1%和2%的酵母培养物YC2(粗蛋白含量为55%)，配制5种等氮等脂 (42%粗蛋白和8%粗脂肪) 的实验饲料，分别命名为C、YC1-1、YC1-2、YC2-1和YC2-2。选择初始体质量为 (4.87±0.00) g 的黄颡鱼375尾，随机分为5组 (每组3个重复，每个重复25尾)，进行为期8周的养殖实验。结果显示，YC2-1和YC2-2处理组黄颡鱼的增重率 (WG) 显著高于对照组，YC2-2处理组的特定生长率 (SGR) 显著高于对照组；YC2-1和YC2-2处理组黄颡鱼肌肉的蛋白沉积率 (PPV) 显著高于对照组，蛋白质效率 (PER) 随着酵母培养物添加水平的上升呈先上升后下降的趋势，YC2-1处理组的PER最高；YC2-1和YC2-2处理组的饲料系数 (FCR) 显著低于对照组，YC2-2处理组的FCR显著低于YC2-1处理组；YC2-1和YC2-2处理组肝脏溶菌酶 (LSZ) 和超氧化物歧化酶 (SOD) 活性均显著高于对照组；YC2-1处理组的肠道皱襞高度显著高于YC1-1处理组，皱襞宽度和上皮细胞高度显著高于YC2-2处理组。嗜水气单胞菌攻毒实验中，酵母培养物组的平均累积死亡率 (CMR) 均低于对照组，YC2-1处理组的CMR显著低于对照组。研究表明，在本实验条件下，饲料中添加酵母培养物YC2能有效改善黄颡鱼机体非特异性免疫功能、提高抗氧化能力、维持肠道健康以及提高黄颡鱼抗嗜水气单胞菌感染的能力。     

黄颡鱼暴发性流行病病原的分离鉴定及其3种毒力基因检测

为查明黄颡鱼(Pelteobagrus fulvidraco)暴发性流行病的病原菌及其3种毒力基因的携带情况,以常规方法进行细菌分离,人工感染试验确定病原菌的致病性,API 20NE和16S rRNA基因序列分析进行细菌鉴定,PCR扩增法检测病原菌的3种毒力基因。结果显示,从发病症状典型的黄颡鱼肝脏中分离到1株嗜水气单胞菌(Aeromonas hydrophila)GXGP1,与嗜水气单胞菌标准株ATCC 7966T的同源性为99.9%,对黄颡鱼有很强致病力,是引起黄颡鱼暴发性流行病的病原菌,该菌携带有Aer、hly和ahp 3种毒力基因。     

不同脂肪源对黄颡鱼幼鱼生长性能、体成分、血清生化指标、体组织脂肪酸组成及抗氧化能力的影响

为研究不同脂肪源对黄颡鱼幼鱼生长性能、体成分、血清生化指标、体组织脂肪酸组成及抗氧化能力的影响,进行为期8周的养殖实验。实验配制了4种分别添加有椰子油(CO)、苏子油(PO)、葵花籽油(SO)、鱼油与葵花籽油1∶1混合油(FO/SO)的等氮等脂的饲料,喂养平均初始体质量为(1.52±0.00)g的黄颡鱼幼鱼。实验结果显示:不同脂肪源对黄颡鱼终末体质量(FBW)、增重率(WGR)、特定生长率(SGR)和成活率(SR)均无显著影响,对饲料系数(FCR)影响显著,各组SR均在95%以上。各组间的肝体比(HSI)、肥满度(CF)均有显著性差异,而脏体比(VSI)和肠脂比(IPR)无显著性差异。HSI和CF均以鱼油与葵花籽油1∶1混合油(FO/SO)组最高,葵花籽油(SO)组最低。黄颡鱼的鱼体水分、粗蛋白和灰分不受饲料脂肪源的影响,而椰子油(CO)组的粗脂肪含量显著高于其他3组,为10.51%,剩余3组间无显著性差异。饲料中脂肪源对黄颡鱼肌肉、肝脏组织脂肪酸组成和含量影响显著,并且肌肉和肝脏中脂肪酸含量变化与饲料中相应脂肪酸含量变化基本一致,椰子油(CO)组组织中饱和脂肪酸(SFA)含量最高,苏子油(PO)组组织中亚麻酸(ALA)和n-3 PUFA含量最高,葵花籽油(SO)组组织中亚油酸(LA)和n-6 PUFA含量最高,而鱼油与葵花籽油1∶1混合油(FO/SO)组组织中脂肪酸较为均衡。黄颡鱼血清中的总蛋白(TP)、白蛋白(ALB)、球蛋白(GLOB)、白蛋白/球蛋白(A/G)、谷草转氨酶(AST)、总胆固醇(CHOL)、甘油三酯(TG)、血糖(GLU)、肌酸激酶(CK)含量不受饲料脂肪源的影响。各组黄颡鱼肝脏中超氧化物歧化酶(SOD)、丙二醛(MDA)、谷胱甘肽S转移酶(GST)活性有显著差异。椰子油(CO)组的SOD和GST活性最高,而MDA含量最低。研究表明,在添加豆油的基础上,椰子油、苏子油、葵花籽油和鱼油与葵花籽油1∶1混合油都可以用作黄颡鱼饲料的脂肪源;证实了鱼体组织中脂肪酸组成基本可以反映饲料脂肪酸组成,并且说明了黄颡鱼具有延长和去饱和ALA和LA的能力。     

慢性氨氮胁迫对史氏鲟幼鱼生长及其肝脏抗氧化、免疫指标的影响

该研究以史氏鲟(Acipenser schrenckii)幼鱼为实验对象,在实验室内营造了0.01 mg·L^?1(对照组)、0.50 mg·L^?1(低浓度组)、1.00 mg·L^?1(中浓度组)、2.00 mg·L^?1(中高浓度组)和4.00 mg·L^?1(高浓度组)5个氨氮浓度组,对史氏鲟胁迫养殖60 d后取样测定其生长、抗氧化和免疫功能的相关指标,初步揭示史氏鲟幼鱼对慢性氨氮胁迫的生理响应。结果显示,随氨氮浓度升高,史氏鲟幼鱼的增重率(WGR)、特定生长率(SGR)、脏体比(VSI)和肝体比(HSI)均显著下降(P<0.05),但肥满度(CF)无显著变化。在抗氧化指标中,随着氨氮浓度的增加,肝脏超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、总抗氧化能力(T-AOC)活性和谷胱甘肽(GSH)含量呈下降趋势,丙二醛(MDA)含量呈上升趋势。免疫指标中,肝脏溶菌酶(LZM)活性和免疫球蛋白M(IgM)含量受氨氮胁迫影响显著(P<0.05)。结果表明,慢性氨氮胁迫显著抑制了史氏鲟幼鱼的生长,降低了鱼体的抗氧化能力和免疫能力。建议在史氏鲟实际养殖过程中,养殖水体中氨氮质量浓度应控制在≤0.5 mg·L^?1,以避免其对史氏鲟造成损伤。     

Effects of feeding frequency on the enzymes and genes involved in oxidative stress in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson) exposed to ammonia

Optimal feeding strategies improve fish growth and health but may be affected by ammonia stress in closed rearing systems such as tanks or ponds. This study aimed to evaluate the effects of feeding frequency and ammonia levels in rearing water on the enzymes and genes involved in oxidative stress of yellow catfish. Experiment (ammonia exposure) and control groups were randomly assigned to one of three feeding frequencies (1, 2 and 4 times daily) for 8 weeks. Weight gain increased as feeding frequency increased from 1 to 4 times daily, but feed conversion ratio values decreased. The highest survival in ammonia group was found when fish was fed 2 times daily. Glutathione peroxidase activity and total antioxidant capacity in liver and brain of fish exposed to ammonia increased as feeding frequency increased from 1 to 4 times daily. Liver malondialdehyde content in control group decreased as feeding frequency increased from 1 to 4 times daily. The lowest liver malondialdehyde content in ammonia group was observed when fish was fed 2 times daily. Liver mRNA expression of superoxide dismutase and catalase in control group increased as feeding frequency increased from 1 to 4 times daily, but the highest superoxide dismutase and catalase expression in ammonia group were observed when fish were fed 2 times daily. This study indicates that higher feeding frequency of yellow catfish exposed to ammonia could result in oxidative stress and poor survival. The optimal feeding frequency of yellow catfish exposed to ammonia is 2 times daily.     

水体铬暴露对南方鲇生长、代谢和铬累积分布的影响

以南方鲇(Silurus meridionalis Chen)幼鱼(19.75±0.12 g)为研究对象,以K_2Cr_2O_7作为毒物源,在(27.5±0.5)℃条件下分别进行了急性暴露和慢性暴露的毒理效应实验。通过急性暴露实验,测得该种鱼的96h半致死浓度值(96 h LC_(50))为56.24 mg/L。在水体Cr浓度分别为0(对照组)、0.937 mg/L(96 h LC_(50)的1/60)和1.875 mg/L(96 h LC_(50)的1/30)条件下,进行了为期8周的慢性暴露实验。结果表明,实验鱼体的特定体重生长率、肥满度和肝脏指数随着Cr浓度的升高而显著降低,肾脏指数随Cr浓度的升高而显著升高;两个Cr浓度组鱼体的蛋白质和能量密度均显著低于对照组,(1/30)96 h LC_(50)浓度组鱼体的脂肪含量显著低于对照组,而前者的水分含量则显著高于后者。两个Cr浓度组鱼体的静止代谢率均显著高于对照组。经过8周水体Cr暴露处理后,实验鱼体的各器官组织中Cr的累积含量均显著高于对照组,其累积含量的顺序均为肾鳃肝肠全鱼脑肌肉;(1/60)96 h LC_(50)和(1/30)96 h LC_(50)浓度组的肾脏的Cr累积含量显著高于其他组织,肌肉的Cr累积含量均显著低于其他组织;鳃组织中Cr含量相对于对照组的增加幅度大大高于其他组织的增幅。     

氨和空气暴露对大鳞副泥鳅组织中谷氨酰胺含量的影响

为研究氨对大鳞副泥鳅(Paramisgurnus dabryanus)(体重18~25 g)生理指标的影响,将其暴露于30 mmol/L NH_4Cl溶液和空气中0 h,6 h,12 h,24 h,48 h,72 h,以研究体外和体内氨对其体组织中谷氨酰胺含量、谷氨酰胺合成酶和谷氨酸脱氢酶活性的影响。研究发现,氨和空气暴露下,随着暴露时间的延长,大鳞副泥鳅肝脏和肌肉组织中谷氨酰胺含量有明显累积的趋势,脑、肝脏和肠道组织中谷氨酰胺合成酶活性均显著上升。氨和空气暴露显著影响大鳞副泥鳅脑和肠道组织中谷氨酸脱氢酶活性,但对肝脏组织中谷氨酸脱氢酶活性并没有显著性影响。结果表明,大鳞副泥鳅可通过体组织中累积谷氨酰胺来应对体外或体内氨浓度的上升,氨暴露和空气暴露可刺激体内谷氨酰胺的合成,将氨转化为无毒性的谷氨酰胺。肠道中谷氨酸脱氢酶活性显著上升,可能在鱼类应对氨氮毒性中,肠道谷氨酸脱氢酶比谷氨酰胺合成酶有更重要的作用。而大鳞副泥鳅肝脏组织中谷氨酸脱氢酶活性并不受氨和空气暴露的影响,这可能是由于肝脏组织中转氨酶催化生成了足量的谷氨酸。     

Dietary α‐Ketoglutarate supplementation alleviates harmful effects of high environmental ammonia on grass carp,Ctenopharyngodon idella

Current intensive fish farming usually causes high environmental ammonia (HEA) in ponds that is toxic to fish. α‐Ketoglutarate (α‐KG) can be rapidly transaminated to glutamic acid and further aminated to glutamine. Therefore, we hypothesized that dietary α‐KG supplementation would alleviate HEA toxicity to fish. To test the hypothesis, 270 healthy grass carp (Ctenopharyngodon idella) juveniles were randomly assigned to control, HEA (18.37 mg/L ammonia) and HEA + α‐KG (0.75% of α‐KG) groups. Ammonia and free amino acid content in plasma and brain, liver glutamic pyruvic transaminase and glutamic oxaloacetic transaminase activity, and urea and glycogen content were measured on the first, seventh and 42nd days. Our results showed short‐term HEA exposure (1 day) led to a significant ammonia accumulation in the brain and plasma and significantly decreased glutamic and aspartic acid content in the brain and increased glutamine content in the brain and plasma. The long‐term HEA exposure (42 days) caused significant reductions in glycine and arginine content in the brain tissue. In most cases, dietary α‐KG supplementation alleviated the fluctuations in FAA content in the brain and plasma. Our results suggested dietary α‐KG alleviated HEA toxicity to grass carp.     

Effects of Yucca shidigera Extract on Growth, Nitrogen Retention, Ammonia Excretion, and Toxicity in Channel Catfish Ictalurus punctatus and Hybrid Tilapia Oreochromis mossambicus × O. niloticus

Nitrogenous waste control in aquaculture systems is necessary to maintain healthy animals and to meet effluent standards. Decreased ammonia production has been attained in traditional livestock production systems by adding extracts of Yucca shidigera to the feed or storage lagoon system. An extract of Yucca shidigera was fed to post yolk-sac and juvenile channel catfish Ictalurus punctatus and hybrid tilapia Oreochrornis mossambicus × O. niloticus to determine the effects on growth, nitrogen retention, ammonia excretion, and toxicity. Post yolk-sac channel catfish fry fed the 1.0-g yucca extract/kg as an agar coating were the only group of experimental organisms that had significantly greater weight gains compared to the control and 0.5-g yucca extract/kg diet groups after 12 wk. Significantly lower fecal nitrogen concentrations were obtained from catfish fed diets containing yucca extract compared to the control groups, although no differences between fecal nitrogen concentrations for catfish fed diets with either 0.5-g or 1.0-g yucca extract/kg diet occurred. Ammonia excretion rates were significantly lower for catfish fed diets containing yucca extract compared to the control group. Accordingly, fish fed diets containing the yucca extract had significantly greater whole-body protein composition, while lipid levels were significantly lower. No significant differences in proximate composition occurred for fish fed any of the diets containing yucca extract, though growth rates were significantly higher than the controls. This study demonstrated that a yucca extract can be used in the diet of channel catfish, and increased growth and decreased ammonia concentrations can be obtained in rearing systems.     

Effects of <Emphasis Type="Italic">Euphorbia hirta</Emphasis> plant leaf extract on growth performance,hematological and organosomatic indices of hybrid catfish, <Emphasis Type="Italic">Clarias macrocephalus </Emphasis>× <Emphasis Type="Italic">C. gariepinus</Emphasis>

This study was conducted to evaluate the effects of Euphorbia hirta leaf extract on the growth performance, hematological and organosomatic indices of hybrid catfish, Clarias macrocephalus?×?C. gariepinus. The fish were treated with 0 (control), 300, 500 and 800 mg/kg (ppm) for 90 days. The weight gain, average daily growth rate, and specific growth rate were at significantly higher levels in fish from all the treatment groups on days 75 and 90, while the feed efficiency and protein efficiency ratio were consistently higher in fish from all the treatment groups from day 60 up until day 90. The feed conversion rate significantly decreased from day 60 until day 90 in all treatment groups when compared with the control group, and the survival rate was significantly different from day 30 until day 90; a consistently higher rate was observed in fish fed 800 mg/kg. The highest viscerosomatic index and intraperitoneal fat were observed in the group fed 500 mg/kg (p?<?0.05). The hepatosomatic index was significantly increased alongside increasing levels of E. hirta extract. The total white blood cell count in the control group was significantly higher on day 30, but on day 90 all the treatment groups showed higher levels. Hematocrit percentage was significantly different on days 30 and 90. Lymphocyte, eosinophil and thrombocyte levels were shown to be significantly different (p?<?0.05) when different groups of fish were compared. In conclusion, 300 mg/kg of E. hirta leaf extract could improve growth performance, hematological and some organosomatic indices in hybrid catfish.     

Changes in physiological parameters involved in glutamine and urea synthesis in Pacific white shrimp,Litopenaeus vannamei,fed Ampithoe sp. meal and exposed to ammonia stress

Two dietary formulas containing 0% (D0 group) and 33% (D33 group) Ampithoe sp. meal were fed to Litopenaeus vannamei for 42 days, and then, an ammonia stress test was performed to explore the mechanism by which dietary Ampithoe sp. meal supplementation improves the ammonia tolerance of shrimp. The changes in key enzyme activities and biochemical substances involved in glutamine and urea synthesis in shrimp under ammonia stress were investigated. The cumulative mortality in the D0 group and D33 group was 62.22% and 44.44% respectively. With the prolongation of ammonia exposure, the ammonia concentration in the haemolymph of both groups increased, but that of the D33 group was significantly lower than that of the D0 group. The glutamate dehydrogenase (GDH) activity, glutamine concentration and urea‐N concentration in the haemolymph of the D33 group were significantly higher than those of the D0 group. In the gills of the D33 group, the glutamine concentration, arginase (ARG) activity and urea‐N concentration were significantly higher than those of the D0 group. In the hepatopancreas of the D33 group, the glutamine synthetase (GS) activity, glutamine concentration and urea‐N concentration were significantly higher than those of the D0 group. In the muscle of the D33 group, the GDH activity, GS activity, glutamine concentration and ARG activity were significantly higher than those of the D0 group. Consequently, our results indicated that dietary Ampithoe sp. meal supplementation could enhance glutamine and urea synthesis, thereby reducing ammonia accumulation in organisms, resulting in the improvement of ammonia tolerance in L. vannamei.     

姜黄素对黄颡鱼(Pelteobagrus fulvidraco)生长、消化与抗氧化能力的影响

选取初始体重为(13.17±0.68) g、初始体长为(11.86±0.53) cm黄颡鱼(Pelteobagrus fulvidraco) 720尾，随机分为6组，每组3个重复，每个重复40尾鱼。分别投喂添加0、50、100、200、400、800 mg/kg姜黄素的实验饲料，分别标记为T1–T6。实验周期为60 d，实验结束后，测定黄颡鱼生长、消化和抗氧化能力指标。结果显示，各实验组特定增长率和存活率均显著高于对照组(P<0.05)，T4组增重率和蛋白质效率显著高于对照组(P<0.05)，T3、T4组饲料系数显著低于对照组(T1组) (P<0.05)；T3、T4、T5组前肠脂肪酶活力显著高于对照组(P<0.05)，T4组前肠淀粉酶活力显著高于对照组(P<0.05)；T6组肝胰脏、T5组脑与T4组头肾超氧化物歧化酶(SOD)活力均较对照组有显著提升(P<0.05)；脑实验各组丙二醛(MDA)含量均显著低于对照组(P<0.05)；T6组肝胰脏、T5组脾脏过氧化氢酶(CAT)活力显著高于对照组(P<0.05)；T4组肝胰脏、T5组脾脏、T5组中肾谷胱甘肽过氧化物酶(GSH-PX)活力显著提升(P<0.05)；血清实验各组GSH-PX活力均显著高于对照组(P<0.05)；肝胰脏实验各组谷胱甘肽(GSH)含量均显著高于对照组(P<0.05)；T5组肝胰脏、T4组脾脏和血清一氧化氮(NO)含量显著高于对照组(P<0.05)。研究表明，在饲料中添加适量的姜黄素可以显著提高黄颡鱼的生长性能、消化能力以及抗氧化能力，以200 mg/kg添加量为最佳。     

Bioaccumulation of cadmium and its biochemical effect on selected tissues of the catfish (<Emphasis Type="Italic">Clarias gariepinus</Emphasis>)

The present study examines the pattern of accumulation of cadmium (Cd) and its biochemical effects on selected tissues of a variety of African catfish (Clarias gariepinus), after exposure to various doses of Cd. The results obtained indicate that at the end of 21 days of exposure, the total tissue organ cadmium concentration followed the pattern kidney > gill > liver > muscle for each of the exposure concentrations. The levels of Cd in these organs were higher than those in ambient water. Moreover, while the rate of uptake of Cd increased with time in the kidney, liver and muscle, it decreased in the gill. Superoxide dismutase (SOD) was significantly elevated only in the kidney of catfish treated with 0.2 and 0.4 ppm of Cd for 7 days compared with the control. Conversely, gill SOD was significantly decreased in the same concentrations of Cd-treated catfish relative to the control. Statistically similar levels of SOD were observed in the liver, brain and muscle with all the treatments after the same duration of treatment. In the fish exposed for 21 days, SOD activity was significantly decreased in the kidney with a corresponding increase in lipid peroxidation (LPO), but it manifested only with the 0.2- and 0.4-ppm Cd treatment relative to the control. In the liver, however, Cd exposure significantly increased SOD in the 0.2- and 0.4-ppm treatments of the same duration. In conclusion, the present study indicates that the accumulation of Cd and its effect on SOD and LPO in C. gariepinus is dependent on concentration, tissue and time