Effect of Dietary Vitamin C on Tissue Vitamin C Concentration in Channel Catfish,Ictalurus punctatus,and Clearance Rate at Two Temperatures-A Preliminary Investigation

Four trials were conducted with channel catfish, Ictalurus punctatus, under controlled laboratory conditions or in earthen ponds, to evaluate effects of dietary vitamin C concentration and feeding period on liver and anterior kidney vitamin C concentration. Clearance rate of vitamin C in liver and anterior kidney was also evaluated in unfed fish or fish fed a vitamin C-free diet. Results indicated that tissue vitamin C concentration is generally proportional to deitary vitamin C concentration, and that it may reach a maximum concentration within 2 weeks in fish fed diets containing vitamin C. Tissue vitamin C may be reduced to a minimum concentration within 2 weeks when fish were not fed or fed with a vitamin C-free diet at a high temprerature (31°). As temperature was reduced from 31 to 10°C there was a 44% and 13.6% drop in liver and anterior kidney vitamin C concentrations, respectively. At 10°C tissue vitamin C remained relatively constant (100 to 120 mg/g for liver, and 200 to 250 mg/g for anterior kidney) for at least 12 weeks if tissue vitamin C was saturated prior to reducing water temperature. Liver vitamin C appeared to be affected more dramatically by dietary vitamin C concentration and cleared more rapidly than anterior kidney during times of vitamin C deficiency.     

Effect of Dietary Protein Concentration and Feeding Rate on Weight Gain,Feed Efficiency,and Body Composition of Pond-Raised Channel Catfish Ictalurus punctatus1

Two experiments were conducted in earthen ponds to evaluate the effect of dietary protein concentration and feeding rate on weight gain, feed efficiency, and body composition of channel catfish. In Experiment 1, two dietary protein concentrations (28% or 32%) and four feeding rates (≤ 90. ≤ 112, ≤ 135 kg/ha per d, or satiation) were used in a factorial arrangement. Channel catfish Ictalurus punctatus fingerlings (average size: 27 g/fish) were stocked into 0.04-ha ponds at a rate of 24,700 fish/ha. Fish were fed once daily at the predetermined maximum feeding rates for 282 d (two growing seasons). In Experiment 2, three dietary protein concentrations (24, 28, or 32%) and two feeding rates (≤ 135 kg/ha per d or satiation) were used. Channel catfish (average size: 373 g/fish) were stocked into 0.04-ha ponds at a rate of 17,300 fish/ha. Fish were fed once daily for 155 d. In both experiments, five ponds were used for each dietary treatment. Results from Experiment 1 showed no differences in total feed fed, feed consumption per fish, weight gain, feed conversion ratio (FCR), or survival between fish fed diets containing 28% and 32% protein diets. As maximum feeding rate increased, total feed fed, feed consumption per fish, and weight gain increased. There were no differences in total feed fed, feed consumption per fish, or weight gain between fish fed at ≤ 135 kg/ha per d and those fed to satiation. Fish fed the 28% protein diet had a lower percentage carcass dressout and higher percentage visceral fat than fish fed the 32% protein diet. Dietary protein concentrations of 28% or 32% had no effect on fillet protein, fat, moisture, and ash. Feeding rate did not affect FCR, survival, percentage carcass dressout, or fillet composition, except fillet fat. As feeding rate increased, percentage visceral fat increased. Fish fed at ≤ 90 kg/ha per d had a lower percentage fillet fat than fish fed at higher feeding rates. In Experiment 2, dietary protein concentration or maximum feeding rate did not affect total feed fed, feed consumption per fish, weight gain, FCR, or survival of channel catfish. Feeding rate had no effect on percentage carcass dressout and visceral fat, or fillet composition. This was due to the similar feed consumption by the fish fed at the two feeding rates. Fish fed the 24% protein diet had lower carcass dressout, higher visceral fat and fillet fat than those fed the 28% or 32% protein diet. Results from the present study indicate that both 28% and 32% protein diets provide satisfactory fish production, dressed yield, and body composition characteristics for pond-raised channel catfish fed a maximum rate of 90 kg/ha per d or ahove.     

Effect of Dietary Protein Concentration on Growth and Processing Yield of Channel Catfish Ictalurus punctatus1

Abstract.— This study was conducted to evaluate the effect of dietary protein concentration and an all‐plant diet on growth and processing yield of pond‐raised channel catfish Ictalurus punctatus. Four diets were formulated using plant and animal proteins to contain 24%n, 28%, 32%, or 36% crude protein with digestible energy to protein (DE/P) ratios of 11.7, 10.2, 9.0, and 8.1 kcal/g, respectively. An all‐plant diet containing 28% protein with a DE/P ratio of 10.2 kcal/g was also included. Channel catfish fingerlings averaging 40 g/fish were stocked into 24, 0.04‐ha ponds at a density of 18,530 fish/ha. Five ponds were used for each dietary treatment except for the all‐plant diet which had four replicates. The fish were fed once daily to apparent satiation for 160 d. No differences were observed in feed consumption, weight gain, survival, carcass and nugget yield, or fillet moisture and protein concentrations among treatments. Fish fed the 28% protein diet had a lower feed conversion ratio (FCR) than fish fed diets containing 24% and 32% protein, but had a FCR similar to fish fed the 36% protein diet. Fillet yield was higher for fish fed the 36% protein diet than fish fed the 24% protein diet. Visceral fat was lower in fish fed the 36% protein diet than fish fed other diets. Fish fed the 32% and 36% protein diets exhibited a lower level of fillet fat than fish fed the 24% protein diet. The 36% protein diet resulted in a lower level of fillet fat than fish fed the 28% protein diet. There was a positive linear regression in fillet yield and fillet moisture concentration and a negative linear regression in visceral fat and fillet fat against dietary protein concentration. No differences in any variables were noted between the 28% protein diets with and without animal protein except that fish fed the 28% protein diet without animal protein had a higher FCR than fish fed the 28% protein diet with animal protein. This observation did not appear to be diet related since FCR of fish fed the 32% protein diet containing animal protein was not different from that of fish fed the 28% all‐plant protein diet. Data from the present study indicate that dietary protein concentrations ranging from 24% to 36% provided for similar feed consumption, growth, feed efficiency, and carcass yield. However, since there is a general increase in fattiness and a decrease in fillet yield as the dietary protein concentration decreases or DEP ratio increases, it is suggested that a minimum of 28% dietary protein with a maximum DEIP ratio of 10 kcal/g protein is optimal for channel catfish growout.     

Effect of Reducing Dietary Digestible Energy to Protein Ratio on Weight Gain and Body Fat of Juvenile Channel Catfish Ictalurus punctatus1

A laboratory feeding trial was conducted to evaluate the effects of reducing digestible energy to protein (DE:P) ratios of practical diets on body fat and weight gain of channel catfish. Five diets were formulated to contain 32, 28, or 24% crude protein with typical DE:P ratios of 8.5, 9.9, or 11.4 kcal/g protein, respectively, and 28% or 24% protein with a reduced DE:P ratio of 8.5 kcal/g protein. Cellulose was used to adjust the DE:P ratio. Juvenile channel catfish Ictalurus punctatus (initial weight: 5.2 g/fish) were fed the experimental diets twice daily to apparent satiation for 12 wk. Fish fed the 28% protein diet with a reduced DE:P ratio of 8.5 kcal/g protein gained less weight and converted feed less efficiently than those fed the 28% protein diet with a typical DE:P ratio of 9.9 kcal/g protein. Fish fed the 24% protein diet with a reduced DE:P ratio of 8.5 kcal/g protein had a similar weight gain but converted feed less efficiently than those fed the 24% protein diet with a typical DE:P ratio of 11.4 kcal/g protein. Weight gain and feed conversion efficiency of fish fed the 32% protein diet with a typical DE:P ratio of 8.5 kcal/g protein were higher than for fish fed other diets except those fed the 28% protein diet with a DE:P ratio of 9.9 kcal/g protein. There were no differences in feed consumption and survival among dietary treatments. Fillet fat of fish fed the 24% and 28% protein diets with a reduced DE:P ratio was lower than that of the fish fed diets containing the same protein concentrations with typical DE:P ratios. At a DE:P ratio of 8.5 kcal/g protein, there were no differences in fillet fat concentration among fish fed diets containing different protein concentrations. There were no differences in fillet protein, moisture, and ash between fish fed the 24% or 28% protein diets containing reduced and typical DE:P ratios. Results from this study show that reducing DE:P ratios in practical diets lowers body fat but also depresses weight gain of channel catfish; thus it would not be economical to use this strategy to reduce body fat of the fish.     

Effects of Dietary Protein Concentration and Feeding Regimen on Channel Catfish, Ictalurus punctatus, Production

A factorial experiment was conducted to examine effects of dietary protein concentration (24, 28, 32, or 36%) and feeding regimen (feeding once daily or every other day [EOD]) on channel catfish, Ictalurus punctatus, production in earthen ponds. Compared with fish fed daily, fish fed EOD had lower feed consumption, weight gain, net production, and percentage of market‐size fish but had high feed efficiency and required fewer hours of aeration. Fish fed EOD also had lower carcass yield, fillet yield, and visceral and fillet fat. There was a significant interaction between dietary protein and feeding regimen for weight gain. No significant differences were observed in weight gain of fish fed daily with diets containing various levels of protein, whereas weight gain of fish fed EOD with a 24% protein diet was lower than those fed EOD with higher protein diets. Results suggest that response of channel catfish to dietary protein levels depends on whether the fish were fed daily or EOD. Feeding EOD to satiation improved feed efficiency and required less aeration compared with fish fed daily but also reduced net production and processing yield; therefore, EOD feeding should be examined closely before implementation.     

Effect of Dietary Protein Concentration and Stocking Density on Production Characteristics of Pond-Raised Channel Catfish Ictalurus punctatus

Diets containing 28% and 32% crude protein were compared for pond‐raised channel catfish Ictalurus punctatus stocked at densities of 14,820, 29,640, or 44,460 fish/ha. Fingerling channel catfish with average initial weight of 48.5 g/fish were stocked into 30 0.04‐ha ponds. Five ponds were randomly allotted for each dietary protein ± stocking density combination. Fish were fed once daily to satiation for two growing seasons. There were no interactions between dietary protein concentration and stocking density for any variables. Dietary protein concentrations (28% or 32%) did not affect net production, feed consumption and weight gain per fish, feed conversion ratio, survival, processing yields, fillet moisture, protein and ash concentrations, or pond water ammonia and nitrite concentrations. Fish fed the 32% protein diet had slightly but significantly lower levels of visceral and fillet fat than fish fed the 28% protein diet. As stocking density increased, net production increased, while weight gain of individual fish, feed efficiency, and survival decreased. Stocking densities did not affect processing yield and fillet composition of the fish. Although highly variable among different ponds and weekly measurements, ponds stocked at the highest density exhibited higher average levels of total ammonia‐nitrogen (TAN) and nitrite‐nitrogen (NO₂‐N) than ponds stocked at lower densities. However, stocking density had no significant effect on un‐ionized ammonia‐nitrogen (NH₃‐N) concentrations, calculated based on water temperature, pH, and TAN. By comparing to the reported critical concentration, a threshold below which is considered not harmful to the fish, these potentially toxic nitrogenous compounds in the pond water were generally in the range acceptable for channel catfish. It appears that a 28% protein diet can provide equivalent net production, feed efficiency, and processing yields as a 32% protein diet for channel catfish raised in ponds from advanced fingerlings to marketable size at densities varying from 14,820 to 44,460 fish/ha under single‐batch cropping systems. Optimum dietary protein concentration for pond‐raised channel catfish does not appear to be affected by stocking density.     

Effects of Dietary Vitamin E Enrichment on Frozen Channel Catfish, (Ictalurus punctatus) Fillets

The storage quality of channel catfish (Ictalurus punctatus), following long term frozen storage, fed diets containing 5 and 10 times the normal level of vitamin E for 45 or 60 days prior to harvest, was evaluated. There were no unusual effects of treatment on fish weight, survival or feed conversion ratios. Muscle vitamin E content was higher (P < 0.05) from fed diets containing supplemental vitamin E than in the control. Oxidation as measured by TBARS and sensory analysis values did not differ (P > 0.05) in response to vitamin E supplementation. Lipid oxidation increased as storage time increased. Lack of change in phospholipid and neutral lipid fractions during storage indicated that autoxidations was the major cause of oxidation in catfish. Vitamin E levels up to 10 times the normal amount did not improve the overall quality of catfish fillets.     

Dietary Folic Acid and Bacterial Infections in Channel Catfish,Ictalurus punctatus

Channel catfish, Ictalurus punctatus, in a quadruplicate flowthrough aquaria for 15 weeks, were fed a semipurified basal diet containing no folic acid or with folic acid levels ranging from 0.2 to 10.0 mg/kg with or without antibiotic. A second study was conducted for 25 weeks under similar conditions but with semipurified diets containing either 20 or 200 mg/kg ascorbic acid and either 0, 0.4, or 4.O.mg/kg folic acid in a factorial design. Mortalities throughout both experiments were monitored and the etiological causes noted. Fish remaining from the second study were overwintered in circular tanks, kept on the same experimental diets, and challenged with Edwardsiella ictaluri after having been on experimental diets for 50 weeks. In both studies, the addition of folk acid to the basal experimental diet resulted in a decreased incidence of columnaris, Flexibacter columnaris. Folic acid concentration in the diet significantly affected mortalities in fish exmrimentallv challenged with E. ictaluri; however, there was significant interaction between the folic acid concentration and the concentration of ascorbic acid. At the lower concentration of ascorbic acid, 4 mg/kg of folic acid was required to reduce mortalities, but at the higher concentration of ascorbic acid, only 0.4 mg/kg folic acid was needed to reduce mortalities below that of the diet without folk acid. Antibody tilers were not affected by folic acid concentration at the lower concentration of ascorbic acid; however at the higher concentration of ascorbic acid, the diets containing 0.4 or 4 mg/kg of folic acid resulted in increased antibody production.     

Phosphorus Availability of Common Feedstuffs to Channel Catfish Ictalurus punctatus as Measured by Weight Gain and Bone Mineralization1

The efficacy of using weight gain and bone mineralization to estimate phosphorus availability from feed ingredients for channel catfish was investigated at the conclusion of a 12-wk feeding trial. Juvenile channel catfish (initial weight = 7.8 g/fish) were fed one of seven test diets each containing phosphorus from a single source. All diets were isocaloric, isonitrogenous, and met all nutrient requirements of channel catfish except for phosphorus, which was assumed to be the factor limiting growth. Phosphorus was considered to be 90% available to fish fed the diet containing monosodium phosphate, but a relative value of 100 was assigned to this treatment for purposes of comparison. All other availability values were calculated relative to this value. Phosphorus availabilities (based on weight gain) for wheat middlings, cottonseed meal, and soybean meal were 38%, 43%, and 49%, respectively, which are in the range previously reported for channel catfish. Phosphorus availability values (based on weight gain) for dicalcium phosphate, menhaden fish meal, and meat and bone/blood meal were 82%, 75%, and 84%, respectively. These values were considerably higher (93–96%) than previously reported for catfish when based on bone ash or bone phosphorus. However, availability data based on weight gain for feedstuffs of animal origin generally agreed with phosphorus availability data reported for rainbow trout. Based on our data, mineral utilization by animals in general, and on known physiology of channel catfish, we suggest that weight gain may be a reliable indicator of phosphorus availability and that phosphorus availability values may be overestimated when base on bone mineralization.     

Enhanced Disease Resistance to Enteric Speticemia in Channel Catfish,Ictalurus punctatus,Administered Lytic Peptide

Lytic peptides have been shown in vitro to be toxic to a wide range of fish bacterial pathogens, including Edwardsiella ictaluri, the causative agent for enteric septicemia. Fingerling channel catfish, Ictalurus punctatus, were challenged with an injection of Edwardsiella ictaluri, and lytic peptide was administered with a single intraperitoneal injection 24 hours later. In a second group, lyptic peptide was also administered by osmotic pump 7 days before the bacterial challenge. A range of peptide concentrations (20-400µg/g fish) was used. Mortalities were recorded for 7 days after injection of bacteria, and E. icraluri was isolated and quantified by standard plate counts from livers. Various tissues were examined for abnormalities due to bacteria and peptide treatment. Fish injected with lytic peptide at 400 µg/g had up to a 95% reduction in bacteria and a 65% reduction in mortality compared to complete mortality in bacteria-injected controls. Fish implanted with osmotic pumps had 99.3% reduction in bacterial counts and had 6% mortality. Tissue samples from infected fish showed changes typical of reaction to immunologic stimuli and infection, while control fish injected with saline or peptide had normal gills, spleens, and kidneys. This study shows the potential for enhancing channel catfish disease resistance to E. ictaluri and other diseases by transferring the gene coding for the lytic peptide into channel catfish.     

Histopathology of Hematopoietic Tissue in Channel Catfish,Ictalurus punctatus,with Anemia

Outbreaks of anemia (CCA) in channel catfish, Ictalurirs punctatus, in Mississippi occur predominantly during spring and fall. Between October, 1990 and May, 1991, twenty-seven cases of CCA were submitted to the Mississippi Cooperative Extension Service-College of Veterinary Medicine Fish Diagnostic Laboratories. Histologic lesions were identified in the head and trunk kidneys of all affected fish. The head kidney contained less than 25% immature hematopoietic tissue in 3 of 22 cases (14%). 25-50% immature hematopoietic tissue in 7 of 22 cases (32%), and greater than 50% immature hematopoietic tissue in 12 of 22 cases (54%). The trunk kidney contained less than 25% immature hematopoietic tissue in 5 of 27 cases (18%), 25-50% immature hematopoietic tissue in 15 of 27 cases (56%), and greater than 50% immature hematopoietic tissue in 7 of 27 cases (26%). The histopathologic findings noted in cases of CCA from Mississippi affect primarily the hematopietic tissues of the head and trunk kidneys.     

Influence of Dietary Levels of Magnesium on Growth, Tissue Mineral Content, and Resistance of Channel Catfish Ictalurus punctatus Challenged with Edwardsiella ictaluri

Juvenile channel catfish were fed purified diets supplemented with magnesium (Mg) from Mg sulfate at levels of 0, 200, 400, 600, 800, and 1,000 mg/kg and 0, 200, 400, 600, and 800 mg/kg in two separate feeding studies. In study I, the effect of dietary levels of Mg on growth response, vertebral mineral content, and macrophage chemotaxis were evaluated. Study II had similar objectives except that whole body mineral content was measured, and resistance of channel catfish to Edwardsiella ictaluri challenge was also determined. Fish with an average weight of 10.89 g were stocked at a rate of 50 fish/110‐L aquarium (study I). In study II, fish with an average weight of 4.14 g were stocked at rates of 40 fish/110‐L aquarium. Prior to stocking, each batch of fish was acclimated to laboratory conditions and fed the basal diet for 2 wk. The concentration of Mg in rearing water was 1.8 mg/L. Each diet was fed to fish in quadruplicate and triplicate aquaria to apparent satiation for 10 wk for studies I and II, respectively. Fish fed the basal diet started to die as early as 3 d after the study began (17 d of feeding the diet without Mg supplementation). In both studies, weight gain, survival, and feed efficiency were lowest for fish fed the basal diet but increased with increasing dietary levels of Mg. However, the differences between the values of each of these parameters for fish fed diets containing supplemental Mg were not always significant. Magnesium‐deficiency signs observed were anorexia, sluggishness, convulsions, deformed snout, vertebral curvature, muscle flaccidity, and high mortality. Vertebral and whole body ash concentrations were high, but Mg content was low for fish fed the basal and the 200‐mg Mg diets. Bone Ca content did not differ among fish fed different diets (study I), but whole body Ca tended to increase for fish fed the basal diet, suggesting the possibility of calcification of soft tissues. Macrophage chemotaxis in the presence of exoantigen was highest for fish fed diets supplemented with Mg at 400 and 200 mgkg for studies I and II, respectively. When expressed in terms of chemotaxis index, however, maximum or near maximum value was observed at a dietary Mg level of 400 mg/kg. Thus, a dietary level of Mg of 400 mg/kg from Mg sulfate was required for optimum growth and survival, maintaining high tissue levels of Mg, prevention of muscle flaccidity and skeletal deformity, and stimulating macrophage chemotaxis. Dietary levels of Mg had no effect on the resistance of juvenile channel catfish to Edwarsiella. ictaluri challenge.     

Effect of Feeding Frequency and Romet-Medicated Feed on Survival, Antibody Response, and Weight Gain of Fingerling Channel Catfish Ictalurus punctatus after Natural Exposure to Edwardsiella ictaluri

Abstract The efficacy of restrictive feeding regimes and Romet®-medicated feed (formulated at 40.5-mg Romet-30 premix/kg feed) fed at 2.0% body weight was evaluated under field trial conditions for the treatment of naturally induced Edwardsiella ictaluri infections in fingerling channel catfish. After detection of an Edwardsiella ictaluri epizootic, fish were fed medicated and non-medicated feed every day, every other day and every third day for the duration of the experiment. In addition, experimental treatments also included fish that were completely withheld from feed and those provided Romet-medicated feed for five consecutive days followed by non-medicated feed fed daily. Feeding frequency and diet significantly affected survival and weight gain. Survival was greatest among fish that were completely withheld from feed or that were fed medicated feed every other or every third day. The use of non-medicated feed every other or every third day was equally as effective for reducing Edwardsiella ictaluri associated mortalities as feeding Romet-medicated feed on a daily basis. Feeding fish Romet-medicated feed for five consecutive days was not an effective treatment. Agglutinating antibody titers against Edwardsiella ictaluri were significantly lower in all groups of fish fed Romet-medicated feed for the duration of the experiment. These data indicate that feeding frequency is a primary factor affecting the severity of Edwardsiella ictaluri infection and that prolonged consumption of Romet-medicated feed may suppress antibody production.     

Effect of Exposure to Potassium Permanganate on Stress Indicators in Channel Catfish Ictalurus punctatus

Juvenile channel catfish Ictulurus punctatus were exposed to 1× (0.44 mg/L), 3× (1.32 mg/L), or 5× (2.19 mg/L) the recommended therapeutic concentrations of waterborne potassium permanganate (KMnO₄) for 36 h to determine the toxicity of the chemical. The fish were observed for 14 d after exposure. Gill, liver, and blood samples were collected before exposure, at 12, 24, and 36 h of exposure, and at 48-h intervals for 14 d thereafter. Analysis of homogenized gill tissue showed a transient increase in manganese content that quickly disappeared once exposure was discontinued. Fish exposed to the 3× and 5× concentrations of KMnO₄ experienced 9 and 50.6% mortality, respectively. Plasma cortisol was elevated more than ten-fold at the 5× concentration. Both plasma chloride and osmolality were significantly reduced at the 3× and 5× concentrations but were unchanged at the 1×. Packed cell volumes (PCV) of whole blood rose significantly in response to 3× and 5× concentrations of KMnO₄ Mortality may have been the result of blood electrolyte depletion as indicated by increased PCVs, loss of chloride, and reduced osmolality. All stress indicators measured, except PCV at the 5× concentration, were indistinguishable from unexposed controls within 48 h after exposure was discontinued. At the l× concentration (the concentration most like that employed in a disease treatment) no changes were observed in any stress indicators measured suggesting that KMnO₄ may be safely used as a disease therapeutant for channel catfish.     

Response of Male Blue Catfish,Ictalurus furcatus,and Male Channel Catfish,Ictalurus punctatus,to Female Channel Catfish Given Pheromonal Steroids or Prostaglandin

The effects of the putative hormonal pheromones 17α, 20β‐dihydroxy‐4‐pregnene‐3‐one (17,20β‐P), 17,20β‐P‐20‐glucosiduronate, and prostaglandin F‐2α (PGF‐2α) injected into female channel catfish, Ictalurus punctatus, were investigated to determine whether male channel catfish and blue catfish, Ictalurus furcatus, could be attracted to the injected females. Females were distributed into traps placed in ponds containing either male channel catfish or blue catfish. Traps were checked six times in a 96‐h period. Males were 17.9 times more likely to be captured with a PGF‐2α‐injected female than with an ethanol‐only injected female, or a 17,20β‐P‐injected female, and 3.5 times more likely to be captured with a PGF‐2α‐injected female than with a 17,20β‐P‐glucosiduronate‐injected female. Males were 6.0 times more likely to be caught between 48 and 96 h post‐injection than between 12 and 24 h post‐injection. These results suggest that the overall best pheromone to attract blue catfish and channel catfish males is PGF‐2α at 48–96 h post‐injection.     

斑点叉尾(鮰)养殖技术及病害防治

我国自美国引进斑点叉尾(鮰),并深入进行了养殖技术研究,已在全国20多个省、市、自治区推广应用,十几年来产值达数十亿元.斑点叉尾(鮰)病害及防治技术的研究,解决了养殖中重大技术难点,它的应用取得了巨大经济效益和社会效益.     

Effects of Dietary Mycotoxins Produced by the Mold Fusarium moniliforme on Channel Catfish Ictalurus punctatus1

Channel catfish Ictalurus punctatus (initial weight: 6.1 g/fish) were fed eight diets containing the mold Fusarium moniliforme-cultured corn supplying 0.7, 2.5, 5, 10, 20, 40, 80, or 240 mg of the mycotoxin, fumonisin B₁ (FB₁)/kg diet under laboratory conditions for 12 wk. Fish fed diets containing FB₁ levels of 40 mg/kg and above showed reduced growth, feed consumption, and feed efficiency, but fish fed FB₁ concentrations of 20 mg/kg and below did not. The minimum level of FB₁ that depressed growth appeared to be between 20 and 40 mg/kg. Hematocrit was significantly lower for fish fed diets containing 80 and 240 mg FB,/kg than for fish fed diets containing lower levels of FB₁. Fish fed diets containing 40 mg FB₁kg and above had increased liver glycogen, increased vacuolation in nerve fibers, and perivascular lymphohistiocytic investment in the brain compared to fish fed diets containing lower levels of fumonisins. Results from this study indicate that FB₁ levels below 20 mg/kg diet are not a problem in commercial catfish feeds. However, it is prudent to screen for fumonisins in feed ingredients.     

酵母免疫多糖对受免斑点叉尾免疫应答的增强作用

在饲料中添加定量的酵母免疫多糖,投喂注射接种了福尔马林灭活的嗜水气单胞菌(Aeromonas hydrophila)菌苗的斑点叉尾(Ictalurus punctatus),28 d后通过测定供试鱼的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性(SGPT)、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了酵母免疫多糖对受免斑点叉尾免疫应答的增强作用。结果表明,用添加200.0 mg/(kg.d)酵母免疫多糖的饲料投喂受免斑点叉尾,不仅可以使受免斑点叉尾对灭活嗜水气单胞菌的免疫应答水平提高,增强抵抗嗜水气单胞菌人工感染的能力,而且还具有一定的促进生长和改善肝功能的作用。     

酵母免疫多糖对受免斑点叉尾(鮰)免疫应答的增强作用

在饲料中添加定量的酵母免疫多糖,投喂注射接种了福尔马林灭活的嗜水气单胞菌(Aeromonas hydrophila)菌苗的斑点叉尾(鮰)(Ictalurus punctatus),28 d后通过测定供试鱼的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性(SGPT)、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了酵母免疫多糖对受免斑点叉尾(鮰) 免疫应答的增强作用.结果表明,用添加200.0 mg/(kg·d)酵母免疫多糖的饲料投喂受免斑点叉尾(鮰),不仅可以使受免斑点叉尾(鮰) 对灭活嗜水气单胞菌的免疫应答水平提高,增强抵抗嗜水气单胞菌人工感染的能力,而且还具有一定的促进生长和改善肝功能的作用.     

壶状臂尾轮虫高效培养技术

2008年4月,四川眉山一水库中养殖的斑点叉尾鮰出现大量死亡,病鱼主要表现为腹部极度膨大,解剖时有大量腹水流出,可见各内脏器官广泛出血.发病最高峰时每天的死亡量可达500多千克,给养殖户带来了巨大的经济损失.经笔者对死亡鱼进行解剖及对致病菌分离、鉴定,最终确定为维氏气单胞菌感染.现将该病例的诊断及防治情况介绍如下.