The economic feasibility of adoption of a new in-pond mechanical grader for food-sized channel catfish (Ictalurus punctatus)

An economic analysis of an in-pond horizontal floating bar grader for food-sized channel catfish was performed. Data from previously reported field trials were used to determine whether farmer adoption of this grader is economically feasible. Scenarios for four farm sizes (65, 130, 259, and 478 ha) were evaluated. Partial budget, payback period, net present value, internal rate of return, and Taguchi quality loss function analyses were used to quantify and compare economic losses due to deviation from the target fish size. Partial budget results indicated positive net revenue for all farm sizes. Net revenue increased with farm size, market price, and increased dockage penalties. Payback periods ranged from 0.1 to 2.0 years depending on the scenario. Net present values were positive and increased with increasing farm size. Estimated internal rates of return were higher than the current opportunity cost of capital and increased with increasing farm size. The value of the gain in quality from reducing size variation from use of the UAPB grader was estimated to range from $770 to $5575/year, depending on farm size. Producer adoption of the UAPB grader is economically feasible for the scenarios analyzed.     

Design and development of a geothermal temperature control system for broodstock management of channel catfish Ictalurus punctatus

A control system was designed to raise and maintain water temperatures within 0.03-ha earthen ponds to a range conducive for spawning (24–30 °C) channel catfish Ictalurus punctatus. Heating was done during February 2001 to April 2001, when temperatures would have otherwise prohibited spawning (<24 °C). Temperature was increased from 10 °C (ambient) by 2 °C per day, and maintained at 27 °C, by the addition of geothermally warmed water (36 °C). The control system substantially increased the controllability and precision of heating ponds compared to manual operation. Systems were designed to control sets of four ponds. In designing this control system, consideration of biological constraints was essential. Reproduction in channel catfish is most strongly influenced by temperature. Because cold fronts are common during the winter and early spring (January–March), it was essential to ensure that pond temperatures did not fall below the range for spawning. Constraints on the heating rate and temperature variability to maintain fish health and stimulate spawning behavior were considered. Components of the control system included temperature measurement devices (type-T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent a message to close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The final design incorporated information on relevant biological parameters and safety features including peak pond temperature, independent aeration and water pressure control mechanisms. Initial results indicate successful control of this biological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives. In particular, this system could be used to vary pond temperatures to study biological responses and to cool ponds by addition of well water during summer months.     

富硒酵母对斑点叉尾鮰肝脏的毒性作用及蛋白质组学的影响

实验探讨了富硒酵母对斑点叉尾鮰肝脏的毒性作用及蛋白质组学的影响,结果表明,饲养56 d后正常组和有机硒组采用原子荧光法检测硒含量均值为0.15和0.81 mg/kg。H.E染色显示有机硒组肝细胞有明显的疏松化,部分发生脂肪变。通过二维凝胶电泳结合ImageMaster软件分析,鉴定出8个表达差异蛋白质点,其中3个在有机硒组表达上调,5个在有机硒组特异表达,经液相色谱串联质谱分析鉴定,这些蛋白质分别是伴侣蛋白TCP1-亚基8、甘油醛-3-磷酸脱氢酶、4SNcTudor蛋白、腺苷激酶、酮糖移转酶、丙氨酰-tRNA合成酶。富硒酵母饲料对斑点叉尾鮰肝具有明显的毒性效应,有机硒调控4SNc-Tudor蛋白,通过信号传导通道加强机体免疫。     

斑点叉尾鲖BPI1基因的原核表达及生物信息学分析

为探究斑点叉尾鲖BPI1抗菌肽基因编码蛋白的结构特征,实验提取斑点叉尾鲖肾脏RNA,根据BPI1基因序列设计引物,利用PCR方法克隆BPI1基因并构建至原核表达载体p TWIN1中。构建成功的重组质粒p TWIN1-BPI1经原核表达,SDS-PAGE检测显示得到约为50 ku的融合蛋白,与预期结果相一致。通过生物信息学软件对BPI1基因编码的蛋白序列进行分析,结果显示,克隆所得斑点叉尾鲖BPI1基因编码一条由223个氨基酸残基组成的多肽,等电点为9.07,属于BPI超家族,是稳定的亲水蛋白。亚细胞定位BPI1分布在线粒体(43.5%)、细胞质(30.4%)和细胞核(26.1%)中,表明BPI1可能在嘌呤和嘧啶合成以及能量代谢等过程中发挥信号转导、促进生长等重要作用。二级结构以α-螺旋和β-折叠为主,三级结构呈棒状。同源性及进化树分析表明,实验所得BPI1基因序列与斑点叉尾鲖BPI抗菌肽基因的同源性最高,序列一致性为99.1%,进化树聚为一支,表明BPI1基因编码的蛋白序列在相同物种中的突变率较低,保守性较高,相同物种中其生物活性与个体间的差异关系较小。     

池塘循环水槽养殖模式下斑点叉尾鮰肌肉特征挥发性风味成分

为探究池塘循环水槽(In-pond raceway system,以下简称IPRS)养殖模式下斑点叉尾鮰(Letaurus punetaus,以下简称鮰)肌肉中特征挥发性风味成分;以传统大池塘养殖(Traditional pond system,以下简称TPS)为对照,利用GC-MS技术对两种模式下的鮰肌肉的挥发性成分进行了萃取和分离鉴定,并结合ROAV确定了不同模式下特征挥发性风味成分;结果显示,IPRS及TPS下分别检测出50种及51种挥发性风味成分,主要由醛类、烃类、醇类及酯类等四大类组成,IPRS鮰肌肉醇类、酮类物质均高于TPS,IPRS下1-戊醇、1-戊烯-3-醇、乙酸乙烯酯、2-壬酮、2,3-辛二酮、1,3-戊二烯、十五烷等物质相对含量显著或极显著高于TPS(P＜0.05或P＜0.01),己醛等部分醛类物质在含量较高时易呈现令人不愉快的气味,IPRS下优势显著。IPRS下特征挥发性风味成分主要包括1-辛烯-3-醇、己醛、庚醛、辛醛、壬醛、2,6-壬二烯醛、癸醛、2,4-癸二烯醛及(E,E)-2,4-壬二烯醛,其中庚醛、2,6-壬二烯醛为TPRS特有的特征挥发性风味成分。结论显示,养殖模式对鮰肌肉挥发性风味成分及相对含量具有较大影响,IPRS下挥发性风味物质构成优于TPS,适合鮰集约化、高密度养殖。     

Comparison of three fish-loading systems to harvest food-size channel catfish (Ictalurus punctatus)

Three fish-loading systems were used to harvest food-size channel catfish (Ictalurus punctatus). Loading rates of equipment and their effect on post-harvest fish survival and weight gain during cool and warm weather were studied.

The turbine pump loading rate (300·7 kg/min) was greater than the lift net (158·00 kg/min) and vacuum pump (54·1 kg/min), while the lift net was greater than the vacuum pump (p < 0·05).

Mean survivals (± SD) for catfish loaded by lift net, turbine pump and vacuum pump from earthen ponds during cool and warm weather were 96·6% (±2·8), 93·9% (±7·4) and 97·7% (±1·1) and 94·0% (±5·7), 85·3% (±8·6) and 89·0% (±12·5), respectively. Mean weight change (± SD) per catfish loaded by the same equipment during cool-and warm-weather tests were −8·2 g/fish (±31·1), −12·4 g/fish (±15·2) and −17·5 g/fish (±19·9), and 67·6 g/fish (±60·6), 33·9 g/fish (±137·4) and 32·4 g/fish (±142·1), respectivley. There were no significant differences among loading systems for survival or mean weight change per fish. The turbine pump is a possible alternative to the traditional life net as a means of loading food-size channel catfish. Further testing on commercial catfish farms is required.     

斑点叉尾鮰鱼骨胶原多肽螯合钙的制备及其特征

以斑点叉尾〖XCF5H.TIF〗鱼骨酶解胶原多肽液和氯化钙为原料,螯合率为指标,在一定条件下制备胶原多肽螯合钙,并考察温度、pH、时间、多肽与钙的质量比对螯合率的影响。在单因素实验结果的基础上,采用BoxBehnken中心组合设计和响应面分析法,确定最佳螯合工艺条件为温度60 ℃、pH 5.4、时间1.5 h、质量比2∶〖KG-*2〗1,此条件下,螯合率达82.53%。紫外吸收和傅里叶变换红外光谱扫描的结果表明,骨胶原多肽与钙形成了螯合物,且其氨基酸组成符合典型的胶原样蛋白特征。     

Development of phytoplankton communities and common off-flavors in a biofloc technology system used for the culture of channel catfish (Ictalurus punctatus)

The use of biofloc technology production systems continues to increase in the aquaculture industry worldwide. Recent research demonstrated that outdoor biofloc systems can be used to produce high yields of channel catfish (Ictalurus punctatus). However, studies have not yet been performed to determine the development and composition of phytoplankton communities and related off-flavor problems in these biofloc production systems. In this study, water samples were collected biweekly from May to November and channel catfish samples were collected during harvest in November from nine 18.6 m² biofloc culture tanks. Water and fillet samples were analyzed for levels of the common off-flavor compounds geosmin and 2-methylisoborneol (MIB). The development and composition of phytoplankton communities in each culture tank was also monitored. In addition, water and biofloc samples were evaluated to assess the microbial sources of geosmin and MIB within the culture tanks. Phytoplankton (including algae and cyanobacteria attached to bioflocs) biomass, as determined by concentrations of chlorophyll a in the water, gradually increased in all tanks over time. Phytoplankton communities that developed in the culture tanks were dominated by fast-growing, unicellular and small colonial types of green algae (chlorophytes) and diatoms (bacillariophytes) and slower growing, small colonial types of cyanobacteria (cyanophytes). A positive correlation (p < 0.05) between cumulative feed addition and chlorophyll a concentration was found. Although geosmin and MIB were present in the culture water of each tank during most of the study, levels were typically low and only one tank yielded catfish with geosmin and MIB in their flesh at levels high enough to be designated as off-flavor. A positive correlation (p < 0.05) between cumulative feed addition and MIB concentrations in the water of culture tanks indicates a greater potential for MIB-related off-flavor problems at high feed application rates. The microbial sources responsible for production of geosmin and MIB in the culture tanks remain unknown.     

液质联用技术测定甲砜霉素及其在斑点叉尾鮰体内的药代动力学

本试验建立了斑点叉尾鮰体内各组织中甲砜霉素的高效液相色谱-串联质谱法,本方法甲砜霉素在5-100 ng/mL浓度范围内呈线性相关,相关系数为0.998,平均回收率在79.05% -95.58%之间,相对标准偏差在2.01%-9.36%之间,血浆中甲砜霉素的定量限为5.0 μg/L,肌肉、皮肤、肾脏、肝脏中甲砜霉素的定量限为5.0 μg/kg。试验在水温为28 ℃条件下,单次口灌（17.5 mg/kg b·w）甲砜霉素,并用高效液相色谱-串联质谱法测定各组织中的药物浓度,采用3p97药代动力学软件处理药-时数据,研究斑点叉尾鮰体内的药代动力学特征。结果表明,甲砜霉素血浆药-时数据符合一级吸收二室模型,血药达峰时间（Tpeak）为8.00 h,血药浓度峰值（Cmax）为933.75 μg/L,药时曲线下面积AUC为12.10 mg/L,消除半衰期（T1/2β）为69.32 h,吸收半衰期（T1/2ka）为4.97 h。药代动力学结果表明,甲砜霉素在斑点叉尾鮰体内呈二室模型分布,以一级药代动力学方式消除。该方法简单可靠,满足甲砜霉素的测定及药代动力学研究的要求。     

饲料中蛋白脂肪比对斑点叉尾鮰幼鱼生长、消化酶活性及肌肉成分的影响

探讨了不同的蛋白和脂肪水平对斑点叉尾生长与品质等的影响,试验设计以豆粕调节蛋白含量,混合油脂(鱼油∶豆油=1∶1)调节脂肪含量,并以α-淀粉和次粉为填充物,共配制3个蛋白(P)水平(28%,32%,36%),每一蛋白水平设3个脂肪(L)水平(5.0%,7.5%,10.0%),共9种饲料,分别为P28L10,P32L10,P36L10,P28L7.5,P32L7.5,P36L7.5,P28L5,P32L5和P36L5,每组4重复,每重复80尾鱼[(1.5±0.02)g]。饲养60d后,进行生产性能测定,并采集肌肉等组织样本,测定相关指标。结果表明:饲料蛋白脂肪比对斑点叉尾幼鱼生长有显著影响(P<0.05)。其中P36L7.5组增重率(WGR)、饲料效率(FCR)最高,与P36L10和P32L7.5组差异不显著(P>0.05),但显著高于其它组(P<0.05)。P36L10组试验鱼肥满度(CF)最高,与P32L7.5和P36L7.5组差异不显著(P>0.05),但显著高于其他组(P<0.05)。鱼体内脏比(VBR)、腹脂率(MSI)随脂肪水平降低而显著降低(P<0.05)。试验各组肌肉水分含量差异不显著(P>...     

饲料低蛋白、高脂肪和高消化能对斑点叉尾鮰

为了探讨高脂肪条件下不同的蛋白和能量水平对斑点叉尾鮰生长及体组成的影响,试验设2个蛋白水平(22%,28%),2个脂肪水平(10.0%,14.0%),2个消化能水平(12.56 kJ/g,14.23 kJ/g),共8组,分别为P28L10E14.23,P28L14E14.23,P22L10E14.23,P22L14E14.23,P28L10E12.56,P28L14E12.56,P22L10E12.56和P22L14E12.56。试验饲料配方使用鱼粉和豆粕调节蛋白含量,混合油脂(鱼油∶玉米油=1∶1)调节脂肪含量,α-淀粉、次粉和麸皮调节消化能含量,并以微晶纤维素为填充物,每组3个重复,每个重复20尾鱼(141.5?1.0) g。饲养60 d后,进行生产性能测定,并采集组织样本,测定相关指标。结果表明,鱼体末重(FW)、增重率(WG)、特定生长率(SGR)和饵料系数(FCR)不受饲料蛋白、脂肪和消化能单一营养水平影响(P>0.05);但与饲料蛋白、脂肪和消化能三者的交互作用(P<0.01)有关。胴体蛋白、脂肪含量与饲料脂肪和消化能水平相关(P<0.05)。由此可见,饲料过高脂肪和消化能对斑点叉尾鮰没有额外的促生长作用;饲料蛋白水平达到22%时,即可满足140~300 g斑点叉尾鮰的营养需要;饲料中22%的蛋白、10%的脂肪、12.56 kJ/g的消化能即可满足斑点叉尾鮰仔鱼的生长需要,同时又能保证其正常生理机能,建议可在实际生产配方中作参考值。     

Water quality and stocking density as stressors of channel catfish (Ictalurus punctatus Raf.)

The influences of heated recirculated water and well water on three stocking densities of channel catfish (Ictalurus punctatus Raf.) were compared, based on several physiological and hematological parameters. Controls were kept in well water only. The leucocyte count of fish kept in well water generally decreased, and their thrombocyte, lymphocyte and granulocyte counts were lower at higher stocking densities. In addition, a slight hemoconcentration was observed. The fish kept in recirculated water showed a decrease only in thrombocyte count. Plasma cortisol and blood glucose did not change and in all groups were at a level characteristic of resting fish. In contrast, the blood lactate levels were always high. This may have been caused by the anesthetization. The alterations found are regarded as symptoms of the “general adaptation syndrome” induced by the stocking rates. High lymphocyte and granulocyte counts among the fish in reused water are signs of local adaptations to reduced water quality.     

鲖爱德华菌口服疫苗对斑点鲖的免疫效果

为评价鲖爱德华菌口服微球疫苗对斑点鲖的免疫效果,实验以天然高分子聚合物海藻酸钠和鲖爱德华菌灭活疫苗为材料,制备鲖爱德华菌口服微球疫苗。将实验动物随机分为鲖爱德华菌微球疫苗组、鲖爱德华菌灭活疫苗组、空微球组和对照组,以拌料口服方式进行免疫,通过检测血清中溶菌酶活力、总超氧化物歧化酶(T-SOD)活力、补体替代途径(ACH50)活性等非特异性免疫指标,抗体效价以及相对免疫保护率评价疫苗免疫效果,采用荧光定量PCR检测口服疫苗对斑点鲖免疫相关基因表达量的影响。结果显示,鲖爱德华菌口服微球疫苗能够较长时间增强斑点鲖非特异性免疫功能;血清凝集效价于第5周达到峰值,为1∶16,免疫后第7周仍可检测到特异性抗体;口服鲖爱德华菌微球疫苗的斑点鲖获得的抗鲖爱德华菌相对免疫保护率为60.7%,远高于灭活疫苗组(14.3%)及空微球组(10.7%);荧光定量分析结果显示,攻毒后48 h相比攻毒前各免疫基因表达量均有上调,鲖爱德华菌微球疫苗对受免鱼肾脏、脾脏中免疫基因的表达影响尤为明显。结果表明,鲖爱德华菌口服微球疫苗能增强斑点鲖非特异性免疫功能,对鲖爱德华菌病起到一定的预防作用。     

Seasonal levels of serum vitellogenin and oocyte growth in the channel catfish Ictalurus punctatus

Seasonal levels of serum vitellogenin (VG) were measured in adult and juvenile (10–30 months old) female channel catfish using an enzyme-linked immunosorbent assay (ELISA). In adults sampled during a 2-year period, the highest mean (±s.e.) VG level was 30.21 ± 5.36 mg/ml in May before spawning and declined to 3.79 ± 0.89 mg/ml in June after the fish had spawned. Oocyte diameter increased from September to November, remained the same until February, then increased again until maximum mean diameter of 2356 ± 49 μm was measured in May. Vitellogenin was detected in the serum of juvenile fish that were 12 months old, but yolk granules were not visible in hematoxylin and eosin stained sections of oocytes until the fish were 18 months old. Mean serum VG levels of juvenile fish were lower than the adults, and no VG peak was observed in the juvenile fish. Vitellogenin was present in the serum throughout the year in adult fish and in juveniles older than 12 months.     

甘草次酸对斑点叉尾（鱼回）免疫应激下血浆抗氧化酶和免疫指标的影响

为探讨斑点叉尾(鮰)免疫应激状态下血浆抗氧化酶和免疫指标的变化,并研究甘草次酸对斑点叉尾(鮰)免疫应激的调控机制,实验设计两组,每组6个重复:1)对照组,饲喂基础饲料;2)GA组,饲喂含0.15 g/kg甘草次酸饲料,养殖8周后,腹腔注射大肠杆菌脂多糖(LPS),分别在注射后0、3、6、12、24、48 h采集血液和肝脏组织,进行红细胞、白细胞计数,分离血浆后检测血浆皮质醇、溶菌酶、ACH50、谷草转氨酶、谷丙转氨酶、碱性磷酸酶活性,肝脏匀浆液检测SOD、MDA和CAT抗氧化酶活性.结果显示,在腹腔注射LPS后,血浆溶菌酶、皮质醇、谷草转氨酶、谷丙转氨酶、ACH50、SOD均呈现先升高后下降的趋势,白细胞计数、血浆CAT呈现先下降后升高的趋势;饲料中添加0.15 g/kg甘草次酸显著抑制了各指标变化,缩短了由LPS诱导产生各指标变化的恢复时间.研究表明,腹腔注射LPS使斑点叉尾(鮰)产生免疫应激,并在注射后6～12h达到顶峰;饲料中添加0.15 g/kg甘草次酸可以有效抑制由LPS诱导的免疫应激反应.     

不同养殖模式对斑点叉尾鮰生长和肌肉品质特性的影响

为探究不同养殖模式下斑点叉尾鮰的生长性能和肌肉品质特性,随机选取传统池塘（TP）、高密度循环水系统（HD-RAS）和水泥池塘（CP）养殖模式下的鲜活斑点叉尾鮰,测定其生长状况,以及肌肉营养成分、颜色、持水力和质构特性。结果显示,TP和HD-RAS的斑点叉尾鮰的增重率和特定生长率差异不显著,但均高于CP;CP的肝体比（2.35%±0.22%）显著高于TP和HD-RAS;与TP相比,HD-RAS和CP肌肉的粗脂肪含量更低,粗蛋白和灰分含量更高;HD-RAS肌肉的亮度值（L*）（58.18±3.56）、红度值（a*）（6.05±1.08）最高,CP最低,分别为48.15±6.04和4.81±0.84;传统池塘养殖的斑点叉尾鮰熟肉率最低,离心损失、滴水损失和失水率最高,HD-RAS和CP之间差异不显著;HD-RAS和CP肌肉的硬度、咀嚼性和弹性显著高于TP,但3处理组间的内聚性和回复性没有显著差异。研究表明,与传统池塘养殖模式相比,水泥池塘养殖模式易造成斑点叉尾鮰生长减慢,而高密度循环水养殖模式对斑点叉尾鮰生长性能没有显著影响,并且在该养殖模式下肌肉具有更高的持水力、质构特性,同时呈现高蛋白、低脂肪的营养特点。     

Enrichment of channel catfish (Ictalurus punctatus) fillets with conjugated linoleic acid and omega-3 fatty acids by dietary manipulation

An experiment was conducted in aquaria with channel catfish (Ictalurus punctatus) to determine the efficacy of augmenting fillets with conjugated linoleic acid (CLA) and omega-3 highly unsaturated fatty acids (n − 3 HUFA) by feeding diets amended with products containing high levels of these nutrients. Refined menhaden fish oil at 1.5% of diet supplied the n − 3 HUFA. CLA was used at dietary levels of 0.5% and 1% with a preparation that contained approximately 65% isomers of CLA. Corn oil was added to the basal diet at maximum inclusion level for added lipids of 3% for the control diet and to adjust total added lipid content of the other diets to 3%. Average initial body weight was 57.39 ± 0.25 g/fish. Six experimental diets were fed twice daily to four replicate aquaria for six weeks. At that time, fish were group weighed for determination of weight gain and feed conversion. Fillets of six fish per aquarium were recovered and stored at − 80 °C for moisture and total lipid analyses, fatty acid analysis, and sensory evaluation. Results showed feed consumption and feed conversion did not differ (P > 0.05). Significantly (P < 0.05) greater body weight gains were observed only for fish fed the diets with two combinations of CLA and 1.5% fish oil compared to fish fed the diet containing 0.5% CLA and corn oil. Fillet n − 3 HUFA levels were significantly (P < 0.05) elevated for fish fed diets containing fish oil when compared to n − 3 HUFA of fillets of fish fed diets containing either corn oil or CLA and corn oil. Similarly, fillets from fish fed diets amended with CLA contained substantial amounts of CLA of up to 6.4% of total lipids. Fillets from fish fed corn oil or fish oil diets had no CLA. Taste panel evaluation indicated that fillets containing n − 3 HUFA and CLA were essentially without fishy off-flavor and had excellent sensory qualities. Catfish fillets produced by amending diets with sources of n − 3 HUFA and CLA at the levels used in this study would contain elevated levels of these nutraceuticals and could be an important human food source for these healthful fatty acids.     

斑点叉尾鮰呼肠孤病毒CCRV诱导CCK细胞凋亡的研究

为研究斑点叉尾(鱼回)呼肠孤病毒(CCRV)诱导斑点叉尾(鱼回)肾脏细胞(CCK)发生凋亡的机理,以CCRV感染的CCK细胞为实验材料,采用Hoechst 33258染色、DNA片段化检测、TUNEL反应、亚G1期细胞检测以及线粒体膜电位变化检测等方法进行实验.感染试验结果显示,病毒感染斑点叉尾(鱼回)肾脏组织细胞后,细胞变圆、皱缩,随后细胞脱落,细胞单层呈网状,感染72 h后出现典型细胞病变效应(CPE);病毒感染48 h后Hoechst 33258染色结果显示,细胞的染色质固缩、核边缘化或破裂,可观察到凋亡小体,细胞凋亡率随时间增加;DNA片段化检测结果显示,病毒感染细胞12 h后细胞基因组DNA出现片段化,随后逐渐增强,72 h达到最高;TUNEL反应结果表明,病毒感染细胞72 h后细胞基因组DNA断裂,有大量游离3’末端自由羟基(-OH)存在.亚G1期细胞检测结果显示,病毒感染48 h后,约53.44％细胞处于亚G1期;利用JC-1检测试剂盒检测病毒感染细胞的线粒体膜电位变化,病毒感染细胞24 h后线粒体膜通透性发生改变,膜电位变化显著.紫外线灭活与热灭活的斑点叉尾(鱼回)呼肠孤病毒不能诱导斑点叉尾(鱼回)肾脏细胞发生凋亡,表明细胞凋亡依赖于病毒复制.     

Growth performance, body composition and plasma thyroid hormone status of channel catfish (Ictalurus punctatus) in response to short-term feed deprivation and refeeding

A 6-week feeding trial was conducted to investigate the effects of short-term feed deprivation on inducing compensatory growth and changes in thyroid hormone levels of channel catfish. Feeding treatments consisted of the following four regimes of 2-week duration: satiate feeding (control), no feed for 3 days then feeding to apparent satiation for the next 11 days, no feed for 5 days then feeding to apparent satiation for 9 days, and no feed for 7 days then feeding to apparent satiation for 7 days. These regimes were repeated three times over the 6-week trial in which 25 channel catfish fingerlings, initially averaging 15 g each, were stocked into each of 12, 38-l glass aquaria supplied with supplemental aeration and flow-through water. Depriving fish of feed had a pronounced effect in that fish lost weight in as little as 3 days. Returning the fish to a satiate feeding regime caused a resumption of growth, equal to control growth only in the case of the 3-day deprived treatment, but all periods of feed deprivation failed to induce a period of catch-up growth adequate to compensate for previously lost weight. Feed efficiency also was not improved by the periods of feed deprivation, and restricting feed in excess of 3 days lowered feed efficiency. Fish condition indices were not altered at the termination of the trial. Muscle lipid, muscle protein and liver protein also were not different among feeding regimes. Liver lipid was elevated in fish deprived of feed for more than 3 days every 2 weeks. Plasma thyroxine (T₄) and triiodothyronine (T₃) were equally depressed by 3 days from the onset of feed deprivation. Both hormones rose significantly within 24 h of realimentation, with the greatest increase observed in animals subjected to the briefest feed deprivation. These results support a role for thyroid hormones in the promotion of growth in channel catfish. Whereas feed deprivation appears to rapidly reduce activity of the hypothalamo-pituitary-thyroid axis, the high correlation observed between T₄ and T₃ in all treatments suggests that peripheral deiodinating systems are capable of rapidly generating T₃ from T₄ upon realimentation. More rapid recovery of thyroid hormone production following realimentation may minimize the effects of feed deprivation on growth and feed efficiency of fish subjected to the 3-day deprivation treatment when compared to longer periods.