Effects of varying dietary compositions using common feed ingredients on growth and feed efficiency of pond‐raised channel catfish Ictalurus punctatus (Rafinesque)

Two experiments were conducted to evaluate various ingredient combinations in a 28% or 32% protein diet for optimum performance of channel catfish Ictalurus punctatus. All diets contained soybean meal and corn, but with or without cottonseed meal, wheat middlings or fish meal (FM). Channel catfish fingerlings were stocked into 0.04 ha earthen ponds at 18 530 fish ha^?1. Fish were fed one of eight diets once daily to apparent satiation for two growing seasons. Results demonstrated that the dietary ingredient composition used had significant effects on fish performance, but magnitude of differences was relatively small. Overall, diets containing FM resulted in greater weight gain (Experiments 1 and 2) and lower feed conversion ratio (Experiment 1) than fish fed all‐plant diets. However, certain combinations of plant ingredients provided the similar fish growth as some diets containing FM. There were no significant differences in weight gain between fish fed soybean meal–corn or soybean meal–corn–wheat middlings‐based diets with cottonseed meal or FM. The use of wheat middlings in the diet had no significant effects on fish production characteristics.     

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.     

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.     

不同饲料料型及投喂频率对斑点叉尾鮰幼鱼生长及肌肉品质的影响

本研究旨在探究不同饲料料型及投喂频率对斑点叉尾鮰(Ictalurus punctatus)生长及肌肉品质的影响。研究采用双因素试验设计,以饲料料型(膨化饲料,EF;颗粒饲料,PF)和投喂频率(2次/日,F2;3次/日,F3)为影响因素,共4个组,分别命名为EFF2、PFF2、EFF3和PFF3,每组3个平行,投喂8周,每天定时投喂两次(7:30和16:30)或3次(7:30, 12:00, 16:30)。结果显示,斑点叉尾鮰的末重和增重率受到投喂频率的影响,F2组显著高于F3组(P0.05);而饲料料型则对斑点叉尾鮰的生长无显著影响(P0.05)。颗粒饲料组的肌肉粗脂肪含量和内聚性、回复性显著低于膨化饲料组(P0.05),而硬度显著高于膨化饲料组(P0.05)。F3组的肌肉硬度、胶着性和咀嚼性则显著高于F2组(P0.05)。颗粒饲料组生肌调节因子5 (myogenic factor 5, Myf5)和肌肉生长抑制素(myostatin,MSTN)基因的相对表达量显著低于膨化饲料组(P0.05)。F3组肌肉中MSTN基因相对表达量显著高于F2组,而肌细胞生成素(myogenin,MyoG)基因相对表达量则呈现相反趋势。综上,投喂同种配方的膨化饲料和颗粒饲料对斑点叉尾鮰的生长效果相似,但是投喂颗粒饲料的斑点叉尾鮰硬度更大,而投喂膨化饲料则肌肉脂肪含量更高;斑点叉尾鮰的最佳投喂频率是每天2次。     

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.     

Kaolinitic clay protects against Flavobacterium columnare infection in channel catfish Ictalurus punctatus (Rafinesque)

Columnaris disease, caused by the bacterial pathogen Flavobacterium columnare, continues to be a major problem worldwide in both wild and cultured freshwater finfish. Despite the far-reaching negative impacts of columnaris disease, safe and efficacious preventatives and curatives for this disease remain limited. In this study, we evaluated the potential of kaolin (Al₂Si₂0₅(OH)₄), a type of clay, for the prevention of columnaris disease. Channel catfish, Ictalurus punctatus (Rafinesque), fingerlings were experimentally challenged with Flavobacterium columnare in untreated water or with water containing kaolin (1 g L⁻¹). Over the 7-day course of study, kaolin treatment led to significantly (P < 0.001) improved survival (96%) as compared to untreated fish (78% survival). Histological examination of the gills revealed that kaolin-treated fish had substantially less gill damage than untreated controls. Quantitative PCR analysis of gill tissue revealed that kaolin significantly reduced F. columnare adhesion (measured at 1 h post-challenge) and colonization (24 h post-challenge). Incubation of kaolin with F. columnare in vitro demonstrated that kaolin reduced the number of F. columnare cells in culture supernatants, presumably through the formation of physical complexes through adsorption. In summary, kaolin can improve survival, reduce gill pathologies and reduce bacterial attachment to key tissues associated with columnaris disease in channel catfish by binding to F. columnare.     

Effects of various corn distillers by‐products on growth,feed efficiency,and body composition of channel catfish,Ictalurus punctatus

A study was conducted to examine the use of corn distillers’ by‐products in diets and the effects of additional dietary fat on channel catfish, Ictalurus punctatus, performance. Juvenile channel catfish (initial weight: 12.6 g per fish) were stocked in flow‐through aquaria and fed one of six practical diets for 9 weeks. Fish fed the control + fat diet consumed more diet and had higher feed efficiency ratio (FER) than fish fed the control diet, but weight gain was not significantly different between fish fed these two diets. Fish fed the diet containing 300 g kg^?1 distillers dried grains with solubles (DDGS) consumed more diet and gained more weight, but had similar FER compared with fish fed the control + fat diet. The diet containing 200 g kg^?1 high‐protein distillers grains (HPDDG) resulted in similar diet consumption, weight gain and FER as the control + fat diet. Fish fed the diet containing 100 g kg^?1 distillers solubles (DS) consumed more diet, but had similar weight gain and FER compared with fish fed the 300 g kg^?1 DDGS diet. The presence of distillers solubles in the diet (300 g kg^?1 DDGS, 100 g kg^?1 DS, 100 g kg^?1 EDS diets) appears to increase diet consumption, weight gain, and FER over the control diets with or without additional fat.     

Early out-of-season induced spawning of channel catfish Ictalurus punctatus (Rafinesque) conditioned in heated earthen ponds

This study documents early out-of-season induced spawning of channel catfish Ictalurus punctatus. During the early spring (February–April) of 1999, 2000 and 2001, ponds containing (1) male and female channel catfish (mixed-sex ponds) or (2) male channel and blue catfish I. furcatus only, or female channel catfish only (single-sex ponds) were heated to 24–30°C to encourage gonadal maturation and spawning. Unheated ponds were stocked with males and females and were monitored during the duration of heating. When natural spawning occurred in the heated ponds, the fish were captured by seining and unspawned females were injected with 100 μg kg⁻¹ of synthetic leutenizing hormone-releasing hormone. Injected females were either paired with males or held in communal all-female groups, and monitored for ovulation. Eggs were collected and fertilized with sperm of channel catfish or blue catfish. Females paired with males were induced to spawn 44 days (mixed-sex ponds) and 50 days (single-sex ponds) before natural spawning occurred in unheated ponds. Spawning latency (the time between injection and ovulation) and the percentage of neurulated embryos from eggs fertilized using channel catfish sperm was not different between spawning before the natural season (P=0.68) and during the natural season in fish from mixed-sex ponds (P=0.57). Females held in all-female groups produced eggs 34 days before the onset of spawning in unheated ponds. Spawning latency was not different between spawns before and during the natural season (P=0.16), and the percentages of neurulated embryos from eggs fertilized with channel catfish sperm (P=0.76) or blue catfish sperm (P=0.77) before or during the natural season were not different. This study demonstrates the feasibility of conditioning of channel catfish females for early out-of-season induced spawning in the laboratory.     

Forecasting monthly catfish (Ictalurus punctatus.) pond bank and feed prices

Volatility in catfish pond bank and feed prices lead to profit uncertainty in the catfish industry. Analysis of the factors that affect those prices and development of a forecasting model would provide guidance to catfish farm managers. Error-correction models (ECM) based on cointegrating relationships among variables were specified following development of a single-equation ARIMAX model. Factors identified as those that influence catfish price were: lagged value of catfish, feed and substitute product prices, while those that influenced feed price were: lagged value of feed, corn and soybean prices. ECM estimates implied that fish price adjusts approximately 6% and feed price 22% to the long-run equilibrium in 1?month. The analysis showed that it takes less than 17?months and 5?months to correct for long-run disequilibrium for catfish and feed prices, respectively. The ARIMAX model demonstrated a better fit for both in-sample and out-of-sample forecasting for catfish price and had better out-of-sample predictive ability for feed prices.     

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.     

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。     

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.