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。     

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.     

Evaluation of cottonseed meal derived from genetically modified cotton as feed ingredients for channel catfish,Ictalurus punctatus

Three laboratory experiments were conducted to assess nutritional quality of cottonseed meals from genetically modified (GM) cotton crops, Roundup Ready^® Flex, Bollgard^® × Roundup Ready, Bollgard II^® × Roundup Ready, and Bollgard II × Roundup Ready Flex for channel catfish, Ictalurus punctatus using Good Laboratory Practices. Growth, feed efficiency, survival, and fillet composition of catfish fed diets containing 20% cottonseed meal from these cotton products were compared with that of catfish fed diets containing cottonseed meals from the near‐isogenic, non‐GM control and non‐GM commercial varieties. Juvenile catfish (mean weights of 4.1, 5.0, and 0.6 g per fish for Experiments 1, 2, and 3, respectively) were stocked in each of 80‐L aquaria and fed experimental diets for 8 weeks. Although there were slight variations in proximate composition, amino acids, and gossypol concentrations, the GM cottonseed meals were not significantly different from the conventional control and the reference cottonseed meals. Weight gain, feed conversion, survival, and fillet composition of catfish fed GM cottonseed meals appeared similar to that of either the control or the commercial cottonseed meals. Results from the present study demonstrate that these GM cottonseed meals are nutritionally equivalent to conventional non‐GM cotton varieties when fed to catfish at 20% of the diet.     

Plasma citrulline and arginine kinetics in juvenile channel catfish, Ictalurus punctatus, given oral gabaculine

Experiments with young mammals have indicated that renal arginine synthesis is a major endogenous source of this amino acid. The kidney readily synthesizes arginine from intestinally derived citrulline, which is produced from glutamate, the so-called intestinal-renal axis. The present experiment was conducted to ascertain whether or not citrulline and arginine are synthesized in channel catfish via this pathway by administering gabaculine, an effective inhibitor of ornithine aminotransferase, and then monitoring circulating levels of arginine, citrulline, glutamate and ornithine. A conditioning diet was fed to apparent satiation to triplicate groups of channel catfish initially averaging 150 g/fish. After 2 weeks of acclimation, fish were lightly anesthetized with MS-222 and were intubated with a gelatin capsule containing gabaculine (3 mg/kg body weight) in one dose. Then, 24 and 48 h after gabaculine treatment, blood plasma was obtained and analyzed for amino acids via HPLC. Oral gabaculine administration significantly (p < 0.05) decreased plasma concentrations of citrulline (–41.8%) and arginine (–8.9%). It also increased (p < 0.05) plasma glutamine (+17.5%) and ornithine (+256.6%). A reasonable explanation for the increase in plasma glutamine and the decrease in citrulline and arginine is offered by the inhibition of glutamine degradation and a decrease in synthesis of citrulline caused by gabaculine. Results of this experiment suggest that endogenous synthesis of citrulline occurs in channel catfish, most likely at the small intestine, and it may serve as a de novo source of arginine. Therefore, the physiological needs of fish tissues and organs for arginine appear to be met via both dietary arginine and the endogenous synthesis of this amino acid.     

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.     

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。     

Effect of lipid supplementation on reproductive performance of female channel catfish,Ictalurus punctatus,induced and strip‐spawned for hybridization

The influence of different lipid sources and n3:n6 ratios on reproductive performance of female channel catfish, Ictalurus punctatus was evaluated. A commercial catfish feed was top coated with 2% oil and offered to brood stock females fish during 70–85 days before spawning season. Four dietary treatments were formulated using the following top coating ratios: diet 1, soybean oil 9.5 g kg^?1 and linseed oil 10.5 g kg^?1; diet 2, soybean oil 17.5 g kg^?1 and linseed oil 2.5 g kg^?1; diet 3, 20.0 g kg^?1 linseed oil, and diet 4, 10.0 g kg^?1 menhaden fish oil, supplemented with 5.0 g kg^?1 arachidonic acid (ARA), and 5.0 g kg^?1 docosahexaenoic acid (DHA). Fatty acid composition of the eggs reflected the effect of dietary treatment offered during spring season. Supplementation of ARA, EPA and DHA in commercial catfish feed in the form of menhaden fish oil with purified liquid algae extracts of ARA and DHA produced from two to five times the number of fry per female body weight when compared to the effect of fed top coated with vegetable oils. Although, this effect was not statistically significant it may represent an economical improvement for the industry.     

Effects of dietary arginine supplementation on growth,protein optimization and innate immune response of channel catfish Ictalurus punctatus (Rafinesque 1818)

Juvenile channel catfish Ictalurus punctatus were fed casein–gelatin‐based semi‐purified test diets with graded amounts of arginine (ARG, 0.5%, 1%, 2% and 4% of dry diet) for a 6‐week period, to evaluate the effects of dietary ARG supplementation on performance indicators, levels of plasma ARG, ornithine, citrulline, glutamine and glutamate, as well as selected innate immune parameters. Incremental dietary ARG resulted in significant improvements in weight gain, feed efficiency and protein efficiency ratios, protein retention, protein deposition and arginine deposition. Fish fed the 4% ARG diet had significantly higher values for all performance indicators, although these values were not different from those of fish fed the 2% ARG diet with the exception of protein retention, protein deposition and arginine deposition. Conversely, fish fed the 0.5% ARG diet had significantly lower values for all analysed plasma amino acids. Similarly, both phagocyte superoxide anion production and neutrophil respiratory burst were significantly decreased in fish fed the 0.5% ARG diet. These results demonstrate that the indispensability of dietary ARG is not only related to optimized protein utilization for growth but also its supplementation to fish diets may significantly impact several aspects of the immune system, including phagocyte function and thus improve overall fish health.     

Comparative growth and yield of channel catfish and channel × blue hybrid catfish fed a full or restricted ration

Growth and yield (kg ha^?1) of the channel catfish (Ictalurus punctatus, Rafinesque, 1818) and the channel × blue hybrid catfish [I. punctatus female ×I. furcatus (Lesueur, 1840) male], which shared the Jubilee strain of channel catfish as the maternal parent, were compared in sixteen 0.1 ha earthen ponds (14 852 fish ha^?1) during the April to November growing season. Each fish genetic group was fed a commercially formulated 32% protein feed daily to apparent satiation or at 80% of the mean daily satiation ration. Net yield and individual weight were higher for channel × blue hybrid catfish compared with channel catfish and for fish fed a full ration compared with a restricted ration. When fed a full ration, the channel × blue hybrid catfish grew faster from May to September than did the purebred channel catfish because the hybrid catfish consumed a greater percentage of its body weight at each feeding. Net yield within each fish genetic group was lower when feed ration was restricted. The per cent reduction in net yield in response to feed restriction was similar for each fish genetic group.     

五个斑点叉尾群体的微卫星遗传多样性分析

用8对微卫星引物对1997-2004年引进的5个斑点叉尾群体进行遗传多样性分析,计算并统计等位基因数、多态信息含量（PIC）、杂合度、遗传相似性系数、遗传距离等参数。实验显示8个微卫星位点在5个斑点叉尾群体中共检测到42个等位基因,平均期望杂合度为0.6338～0.7320,表明其遗传多样性程度处于中等偏上水平。平均多态信息含量为0.5756～0.6869,说明基因座为高度多态基因座（PIC〉0.5）。群体间遗传相似系数为0.7504～0.9203。聚类分析显示,04群体与其他4个群体的亲缘关系较远。结果表明：引进的5个斑点叉尾群体均具有较高的遗传多样性,遗传信息丰富,遗传变异大,为良好的育种材料。     

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.     

投喂频率对斑点叉尾鮰幼鱼生长、饲料利用和鱼体组成的影响

通过8周的生长试验,研究斑点叉尾鮰(Ictalurus punctatus)幼鱼(初始体重约4.5 g)的最适投喂频率。试验饲料为自制配合饲料,粗蛋白38%,总能19.0 kJ/g。设计了1～5次/d(M1-M5)5种投喂频率。结果表明:M2、M3、M4组摄食率均显著高于M1和M5组(P<0.05),其中M4组最大。M3、M4、M5组的特定生长率均显著高于M1组(P<0.05),其中M3组最大。M2、M3、M4、M5组的干物质表观消化率均显著高于M1组(P<0.05),M3和M4组的蛋白和能量表观消化率均显著高于M1和M2组(P<0.05)。M3组干物质含量显著高于M1和M2组(P<0.05),M2、M3、M4和M5组的粗蛋白、粗脂肪和能量含量均显著高于M1组(P<0.05)。因此,本研究建议,斑点叉尾鮰幼鱼养殖的最适投喂频率为3次/d。     

Susceptibility of channel catfish (Ictalurus punctatus) fed with dietary sodium chloride to nitrite toxicity

Juvenile channel catfish (Ictalurus punctatus) were fed with nutritionally complete, basal diets supplemented with NaCl at 0, 10, 20 or 40 g kg^?1 diet (0, 1, 2, or 4%) to apparent satiation twice daily for 10 weeks. Catfish were exposed to nitrite after six (7.70 mg L^?1 nitrite‐N) and ten (7.18 mg L^?1 nitrite‐N) weeks of feeding to determine the effect of dietary NaCl supplementation on resistance to nitrite toxicity. Fish were sampled before (baseline, pre‐exposure) and after 24‐h nitrite exposure to determine the effects of dietary NaCl on haematology (haematocrit, haemoglobin and methaemoglobin) and plasma electrolyte dynamics (nitrite, chloride, sodium and potassium). Mortality from nitrite toxicity was also determined. Mortality from nitrite exposure tended to decrease with increasing NaCl in the diet at 6 weeks and was significantly lower in the 40 g kg^?1 NaCl group (12.5%) compared to the control group (57.5%). A similar trend in mortality occurred at 10 weeks as well; however, the differences among dietary treatments were not significant. The improvements in blood MetHb (non‐significant), chloride and nitrite levels in catfish may at least in part be responsible for the improved survival after nitrite exposure, which trended in support of the prevailing hypotheses for the positive effects of NaCl on nitrite toxicity.     

Nutritional value of frass from black soldier fly larvae,Hermetia illucens,in a channel catfish,Ictalurus punctatus,diet

Frass is the by‐product of the larval meal industry and includes larval waste, exoskeleton sheds and residual feed ingredients. Experimental frass was derived from the larvae of black solder flies fed distillers' dried grains with solubles and had a protein and fat content of 216 and 60 g/kg, respectively. A 10‐week study was conducted to evaluate the effect of dietary levels of frass on growth, feed utilization, and body proximate and mineral composition of channel catfish, Ictalurus punctatus. Five diets containing 0, 50, 100, 200 and 300 g frass per kg diet were fed to channel catfish (5.24 ± 0.04 g) in quadruplicate aquaria to apparent satiation twice daily. Final weight gain was significantly increased in fish fed diets containing frass at levels from 100 to 300 g/kg. Fish fed diets without frass, and with 300 g/kg frass, showed the lowest and highest feed intake, respectively. Feed and protein efficiencies, however, were significantly lower in fish fed frass at levels of 200 g/kg and higher compared to the control diet. Survival, whole‐body composition and mineral content were not affected by frass. In summary, black soldier fly larval frass has potential as a protein source or just an ingredient for enhancing palatability of catfish diets.     

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.