Economic analysis of overwinter feeding regimens for channel catfish (Ictalurus punctatus)

Abstract

Overwintering is a major source of uncertainty for US catfish farmers, particularly decisions on feeding. To address this issue, economic analysis was undertaken using results from pond experiments. Three overwintering strategies (full‐feed, partial‐feed, and no‐feed) for two year classes of catfish were compared. Year 1 fin‐gerlings were 22 g and year 2 fish were 420 g at stocking. Winter feeding was based on temperature and body weight percentages; (1) full‐feeding followed the regime during the November to April period; (2) partial‐fed treatments followed the temperature/body weight regimen only during the months of November, March and April, with no feeding during the coldest months of December to February; and (3) no‐feeding treatments received no feed during the overwinter period. Cost and returns were estimated for each alternative and each alternative was assessed using: (1) overwinter period experimental results, (2) overwinter period experimental results extended through the grow‐out period, (3) overwinter period experimental results extended to minimally acceptable fish sizes, and (4) adjusted estimates to reflect commercial‐scale practices. Sensitivity analyses on feed conversion ratios, stocking rates and fish selling prices were also conducted on commercial‐scale enterprises. Results consistently showed partial‐fed overwinter practices to be most profitable. Secondly, year 1 fish always had higher returns than year 2 fish due largely to the additional overwintering period and associated variable and fixed costs incurred by the year 2 fish production practices. The data upon which this analysis was based do not include the possibility of having a harvest‐sized fish going into the winter period.     

Vibriosis in channel catfish, Ictalurus punctatus (Rafinesque)

Abstract. An epizootic due to Vibrio anguillarum was observed in channel catfish, Ictalurus punctatus (Rafinesque). Lesions in infected fish included ulceration and petechiae on body surfaces, vent and caudal peduncle. Internally, haemorrhages in liver and kidney were present and the intestinal tract was filled with a clear viscous fluid. Using an isolant recovered during the epizootic, laboratory studies were conducted to determine (a) bacterial dynamics of the agent in blood, kidney and liver and (b) clinical haematologic and biochemical parameters in infected fish. Under conditions of the study, vibrios were apparently sequestered in kidney and liver during initial stages of infection (8–12 h after exposure). Later, bacterial numbers in blood were comparable to those in kidney and liver. Clinical parameters of infected catfish were suggestive of cellular and tissue destruction and renal dysfunction. Based upon data of the present study and those of others, vibriosis appears to be a disease in which the agent is localized in select tissues. Secondary septicaemia may be incidental to factors which compromise host defences.     

三聚氰胺在斑点叉尾鮰体内的残留及代谢规律研究

(21±1)℃水温条件下,研究了三聚氰胺在斑点叉尾鮰(Ictalurus punctatus)体内的残留消除规律。结果显示:血浆中药时数据符合有吸收一室开放模型,动力学方程为:C=3.952660(e-0.027279t-e-0.127279t),吸收半衰期(T1/2kα)为5.4469 h,消除半衰期(T1/2ke)为25.4093 h,达峰时间(Tp)为15.4045 h,达峰浓度(Cmax)为20.3985 mg/L,表观分布容积(Vd)为2.5763(mg/kg)/(mg/L)。肌肉、肝、肾中吸收半衰期(T1/2kα)分别为3.5582、4.1884、5.4397 h,消除半衰期(T1/2ke)为50.8081、23.3504、23.7242 h,达峰时间(Tp)为14.6766、12.6524、14.9967 h,达峰浓度(Cmax)为7.6449、22.9249、40.6047 mg/L,表观分布容积(Vd)为8.5657、2.3970、1.2712(mg/kg)/(mg/L)。结果表明:药物在体内吸收迅速,药物浓度较高,分布广泛,消除较为缓慢。以80 mg/kg剂量混饲口灌3 d后,各组织中三聚氰胺含量总体呈现肾脏>肝脏>肌肉。停止灌药后第5天肌肉中及第7天肝脏和肾脏组织中三聚氰胺含量低于我国(2008)卫生部公布的乳制品及含乳食品中三聚氰胺临时管理限量值和欧盟对中国进口产品设定了三聚氰胺的最大残留限2.5 mg/kg。     

Branchiomyces infection in farm-reared channel catfish, Ictalurus punctatus (Rafinesque)

Four cases (representing outbreaks in four different ponds on three farms) of branchial mycosis caused by Branchiomyces spp. were identified in channel catfish fry during the summer of 1996. Mortalities ranged from a few hundred to several thousand fish per pond. Significant gross and histopathological findings from these four cases were limited to the gills. All fry examined had fungal mycelia that were mainly but not entirely confined to the base of the primary lamellae and the gill arches. These fungal hyphae were intravascular and occluded vessels in the gill tissues. The present paper describes the fungal characteristics and pathology of branchial mycosis caused by Branchiomyces spp. in channel catfish.     

斑点叉尾鮰血浆铜蓝蛋白的全长cDNA克隆及表达特征分析

本研究克隆了斑点叉尾鮰中血浆铜蓝蛋白基因全长cDNA序列,其中5′非翻译区(5′-UTR)25 bp、3′非翻译区(3′-UTR) 860 bp、开放阅读框(Open reading frame,ORF) 3 225bp,编码一条含有1 074个氨基酸的多肽链。与其他真核生物血浆铜蓝蛋白成员进行同源性比较,表现出较高的保守性。本研究利用荧光实时定量PCR技术分析了斑点叉尾鮰血浆铜蓝蛋白基因在正常组织和被不同病菌感染后的肝脏、肠、头肾及脾脏中的表达。结果发现,正常组织中血浆铜蓝蛋白基因在正常肝脏中表达最强烈。4种病原（迟钝爱德华氏菌、海豚链球菌、嗜水气单胞菌和斑点叉尾鮰呼肠孤病毒）引起的血浆铜蓝蛋白基因的应答在不同组织中都有差异。血浆铜蓝蛋白基因对海豚链球菌的应答最为显著,而对呼肠孤病毒的应答最不明显。而且不难发现,感染4种病原菌后,血浆铜蓝蛋白基因在头肾中的表达都出现明显的上调。     

Effect of supplemental taurine on juvenile channel catfish Ictalurus punctatus growth performance

Juvenile channel catfish (5.6 g/fish) were fed a basal diet that contained major protein (soybean meal, cottonseed meal) and energy (ground corn grain, wheat middlings) ingredients that were derived from plant sources. The basal diet was supplemented with three levels of crystalline taurine to provide 1, 2 and 5 g/kg taurine. In addition, a fifth diet that contained 80 g/kg menhaden fishmeal formulated with the same plant‐source ingredients was included as the positive control diet. Fish were fed the five diets once daily for 12 weeks. Weight gain was highest in catfish fed taurine at 2 g/kg (47.8 g/fish) compared to catfish fed the control basal diet (40.8 g/fish) and 80 g/kg fishmeal diet (41.1 g/fish) (p < .05). Among the taurine‐supplemented diets, weight gain was lowest in catfish fed taurine at 5 g/kg. Feed conversion ratio (FCR) was significantly improved in fish fed diets supplemented with taurine at 2 g/kg compared to all other treatments (p < .01). Survival during the growth study ranged from 98.0 to 99.0% (p > .05) for all treatments. The results suggest taurine supplementation to juvenile channel catfish may improve weight gain and FCR.     

斑点叉尾鮰肌肉营养成分分析

取15尾斑点叉尾鮰为样品,测定其含肉率和肌肉的营养成分。结果为:含肉率为75.71％;肌肉中粗蛋白占19.42％,脂肪占1.01％,水分占77.58％,灰分占1.12％,碳水化合物占0.87％;肌肉中含有18种氨基酸,占肌肉总量的18.72％,其中人体必需氨基酸占总氨基酸的42.26％。矿物质含量中Fe、Zn的含量较高,而对人体健康有害的物质如Pb、As等的含量很低。笔者认为斑点叉尾鮰是一种营养价值比较全面的淡水养殖品种,具有良好的养殖前景。     

Measurement of channel catfish (Ictalurus punctatus) plasma insulin in species-specific radioimmunoassay

A single antibody, equilibrium, species specific radioimmunoassay (RIA) for catfish insulin was developed and validated for measurements of plasma levels of insulin in juvenile and adult channel catfish. The RIA appeared to be sensitive (20 pg/tube) and stable with intra-assay coefficient of variation between 5.7% and 3.1% and inter-assay coefficient of variation of 6.5%. The blood was collected from two strains of catfish, USDA 103 and Norris, which differ in food consumption and growth rates, the former strain consuming more food and growing faster (Silverstein et al. 1999). The experiments conducted from December to May included fasting and feeding periods from 5 to 14 days as well as either intravenous or intraperitoneal administration of glucagon-like peptide known for its anorexic effect in both mammals and fish (Silverstein et al. 2001). As in other piscine species studied before, fed fish had higher plasma insulin content than food-deprived fish. Feeding status prevailed over other treatments as the primary physiological factor determining circulating plasma insulin levels. This revised version was published online in August 2006 with corrections to the Cover Date.     

甘露寡糖对斑点叉尾鮰成活率及生长的影响

在水库中选用8个网箱进行斑点叉尾鮰的养殖试验,网箱分为试验箱和对照箱2个组,每组设4个平行.在试验组的斑点叉尾鮰饲料中添加甘露寡糖进行投喂,甘露寡糖添加量为鱼体重的0.15‰,对照组不添加,试验时间60 d.结果表明,试验组斑点叉尾鮰成活率为94.51%,对照组为87.01%,高出7.5个百分点.随着投喂时间的延长,试验组斑点叉尾鮰的死亡率呈明显下降趋势,至试验结束时的第55～60天,死亡率比对照组的同一时间段下降了10倍;试验组斑点叉尾鮰体重的增加比对照组快16.5%,差异极显著(P<0.01).     

Detection of channel catfish virus in asymptomatic adult channel catfish,Ictalurus punctatus (Rafinesque)*

Abstract. Two populations of channel catfish were examined for the presence of channel catfish virus (CCV) by use of a nucleic acid probe. In one population of 22 fish with no history of CCV, viral DNA was found in every liver. These fish had previously been examined by a technique involving co-cultivation of their leucocytes with catfish tissue culture cells. The co-cultivation method had identified virus in 10 of these fish. The second fish population consisted of 14 adults that had survived a CCV outbreak in 1980. Of the 14 fish, 11 showed positive indication of CCV DNA. The tissue distribution of the CCV differed from fish to fish. All fish from the first group and one fish from the second group showed some alterations in the DNA banding patterns expected from pure CCV DNA. This might be indicative of modifications in the genomic structure of the CCV DNA when the virus is latent in a fish.     

Logit models for evaluating spawning performance of channel catfish, Ictalurus punctatus (Rafinesque)

Broodstock evaluations are often measured by variables such as spawning success, fecundity, fertilization and hatching rates, usually expressed as percentage values. Outcomes are generally analysed as continuous random variables, assuming that they follow a normal distribution. Ordinary linear regression models (e.g. analysis of variance) as well as χ² analysis are typically applied. However, these models may not be the most appropriate as a number of test criteria may not be met. For example, spawning success outcomes are inherently discrete and non‐negative data and hence their distribution is not likely to be normal. As these models may not be the most appropriate, a case study using logit analysis as an alternative method for the evaluation of this type of data is presented by considering the response as binary data (spawned versus did not spawn). An exact version of logit analysis was performed due to the sparseness of the data. The results demonstrate that appropriate statistical models provide better insight into the cause–effect relationships that exist between control variables and the dependent variable (likelihood of spawning in this case). As would be expected, each strain of fish responded somewhat differently to the test variables. Changing the protein level of the diet from 32% to 42% or increasing the feeding frequency from three to six times per week either did not influence spawning or negatively affected spawning respectively. Additionally, older fish performed better than younger fish and the early spawning period was better than the later spawning period, regardless of strain. These responses, however, were only detected using logit analysis, which is a more sensitive test and would thus be recommended for this type of data.     

Histological effects of prolonged sublethal hypoxia on channel catfish Ictalurus punctatus (Rafinesque)

Abstract. A vacuum degassing apparatus was used to subject channel catfish Ictalurus punctatus (Rafinesque) to sublethal hypoxia for 24, 48 or 72 h. Spleen, liver, gills, anterior kidney and posterior kidney from the catfish exhibited histopathological changes that included necrosis, hyperaemia, oedema, haemorrhage, hyperplasia and hypertrophy. Of the organs examined, gills were most affected by the hypoxic conditions. After 5 days of reacclimatization to normoxic conditions, channel catfish continued to exhibit histopathological effects of prolonged hypoxia.     

斑点叉尾 源嗜麦芽寡养单胞菌的脂质体疫苗研究

采用反相蒸发法制备嗜麦芽寡养单胞菌的脂质体疫苗,通过灌胃分别给予各组斑点叉尾(鮰)(Ictalurus punctatus)脂质体疫苗(Ⅰ-Ⅲ组)、嗜麦芽寡养单胞菌灭活苗(Ⅳ组)和生理盐水(Ⅴ组),每2周给药1次,共3次.于接种疫苗后第1天、14天、28天和第49天采集静脉血,测定白细胞的杀菌活性和血清抗体IgM含量的变化,并用细菌攻毒实验检测免疫保护效应.结果显示,本实验制备的脂质体疫苗粒径约为(0.9±0.3)μm,包封率为53.23%,与嗜麦芽寡养单胞菌灭活苗相比能显著增强斑点叉尾(鮰)吞噬细胞的杀菌活性和血清抗体:IgM水平.腹腔注射活菌攻毒后,脂质体疫苗免疫的Ⅰ-Ⅲ组的相对免疫保护率分别为34.8%、48.2%和55.4%;而嗜麦芽寡养单胞菌灭活苗免疫的Ⅳ组的相对免疫保护率仅有6.7%,生理盐水对照Ⅴ组保护率则为零.研究表明,口服脂质体疫苗对斑点又尾(鮰)具有显著的免疫保护效应,可作为预防嗜麦芽寡养单胞菌感染的疫苗.     

斑点叉尾鳃健康养殖技术

斑点叉尾回属鲇形目回科鱼类,自然分布于美国中北部和加拿大南部各江河流域,肉间细刺少且营养丰富、肉质鲜美.为美国主要淡水养殖鱼类之一,具有生长快、抗病力强、食性杂、易垂钓等特点.80年代被引进我国,现已在我国部分地区开展养殖,希望以此文推动业界对这一品种的重视和开发.