Effect of Replacing Menhaden Oil with Catfish Oil on the Fatty Acid Composition of Juvenile Channel Catfish, Ictalurus punctatus

The effect of using a finishing diet containing menhaden fish oil on the fatty acid composition of fingerling channel catfish, Ictalurus punctatus, was evaluated in a 12‐wk growth trial. Three isocaloric, isonitrogenous practical diets with three different sources of lipids (menhaden oil [MO], catfish oil [CO], or beef tallow [BT]) were formulated (35% crude protein). No differences in eicosapentaenoic acid, docosahexaenoic acid, or arachidonic acid were observed to occur in catfish fed MO or CO diets; however, these fatty acids were significantly lower in fish fed BT diet. No differences were observed for unsaturated fatty acid content in channel catfish fed a diet containing MO for 8 or 12 wk. In addition, no differences in production characteristics were observed to occur when catfish were fed diets containing CO, MO, or BT as the dietary lipid source, which indicates that BT, CO, and MO are equally effective as sources of energy. It is apparent from these results that CO may be successfully substituted for MO in formulated diets without adversely affecting n‐3 highly unsaturated fatty acid content in channel catfish.     

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.     

Comparison of Various Animal Protein Sources for Growth, Feed Efficiency, and Body Composition of Juvenile Channel Catfish Ictalurus punctatus

A laboratory study was conducted to compare different animal protein sources in diets containing 32% protein for channel catfish Ictalurus punrtatus . The experimental diets were practical-type diets and formulated to meet or exceed all known nutrient requirements for channel catfish. Twenty juvenile channel catfish (initial weight: 6.4 g/fish) were stocked into each of 25 110-L flow-through aquaria (five aquaria/treatment). Fish were fed twice daily to approximate satiation for 9 wk. Fish in each aquarium were counted and weighed collectively every 3 wk. No significant differences were observed in feed consumption, weight gain, feed efficiency, survival, percentages visceral fat and fillet yield, or proximate composition of fillets among channel catfish fed diets containing either 5% menhaden fish meal, meat and bone/blood meal, catfish by-product meal, poultry by-product meal, or hydrolyzed feather meal with supplemental lysine. The data indicate that these animal protein sources can be used interchangeably in diets for channel catfish without affecting fish growth, feed efficiency, or body composition.     

Behavioral Interactions in Juvenile Channel Catfish,Ictalurus punctatus

Behavioral interactions among juvenile channel catfish, "Ictalurus punctatus," were observed, and fixed action patterns were described and anlyzed. Dominant fish engaged regularly in aggressive activities and never in submissive activities, whereas subordinate fish were observed in submissive activities on a regular basis and rarely in those that were aggressive. Activity levels were significantly higher in dominant fish; however, there was no difference in activity levels between pairs of equal and unequal size fish. A factor analysis indicated that there were three general categoris of behavior in juvenile channel catfish. In addition, two behaviors (which appeared to be displacement activities) were functioning in agnostic encounters. Plasma cortisol concentrations measured in sigle fish and pairs of fish in aquaria and individuals from a holding tank indicated that the least amount of stress occurred in fish that were not interacting with any other individuals. Cortisol levels, however, were lower that those associated with stress levels in fish from other studies.     

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.     

Effects of Periodic Feed Deprivation on Growth, Feed Efficiency, Processing Yield, and Body Composition of Channel Catfish Ictalurus punctatus

Two studies were conducted in 110‐L flow‐through aquaria and 0.4‐ha ponds to evaluate effects of periodic feed deprivation on the growth performance of channel catfish Ictalurus punctatus. Fish were deprived of feed 0, 1, 2, or 3 consecutive d/wk, l d per 5‐d period, or 3 consecutive d per 10‐d period and fed to satiation on days fish were fed. In Experiment 1, fish fed less frequently than daily consumed significantly less feed (over the experimental period) and gained significantly less weight than fish fed daily, except that feed consumption of fish deprived of feed 1 d/wk was not significantly different from that of fish fed daily. Compared with fish fed daily, fish deprived of feed 2 d/wk had significantly lower feed conversion ratio (FCR). Visceral fat of fish deprived of feed 1 or 2 d/wk was similar to that of fish fed daily, but fish deprived of feed for longer periods had significantly lower visceral fat than fish fed daily. Regression analysis indicated that feed consumption, weight gain, and visceral fat increased linearly as the number of days that fish were fed increased. In Experiment 2, there were no significant differences in the amount of feed fed between fish deprived of feed 1 d/wk and those fed daily. Net production of fish deprived of feed 1 or 2 d/wk or 1 d per 5‐d period was not significantly different from that of fish fed daily, but fish deprived of feed for longer periods had significantly lower net production than fish fed daily. Visceral fat of fish deprived of feed 1 d/wk or 1 d per 5‐d period was similar to that of fish fed daily, but fish on other treatments had significantly lower visceral fat than fish fed daily. Regression analysis showed that as the number of days fed increased the amount of feed fed and net production increased quadratically. Feed conversion ratio, carcass yield, visceral fat, and fillet fat increased, while fillet moisture decreased linearly as the number of days fed increased. Although feeding less frequently than daily may improve feed efficiency, and fish deprived of feed may demonstrate compensatory growth when a full feeding regime is resumed, it may be difficult to provide enough feed to satiate all size‐classes of fish under a multiple‐batch cropping system without causing water quality problems. Under normal economic conditions, fish should be fed daily to apparent satiation without waste and without causing water quality problems. However, during periods of unfavorable economic conditions, channel catfish raised from advanced fingerlings to market size may be fed less frequently than daily to reduce production cost. Results from the present study indicated that feeding channel catfish to satiation 5 or 6 d/wk (not feeding on one or two weekend days) could provide some benefits in reducing production cost through reduced feed and labor costs for food‐sized channel catfish during periods of low fish prices and high feed prices.     

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.     

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.     

Effects of Dietary Protein Level and Feeding Regimen on Growth and on Fattiness of Channel Catfish,Ictalurus punctatus

Two studies were conducted to evaluate the effects of (I) high-protein (38%) finisher feed fed to satiation for 30,45,60, or 90 days prior to harvest and (2) dietary protein (32 vs. 38%) and feeding regimen (satiation or restricted) on growth and fattiness of channel catfish. Each study was conducted for two years in earthen ponds stocked with channel catfish at a rate of 13,590 fish/ha (35 to 40 g initial weight) for year 1 and 6,800 fish/ha (0.45 to 0.6 kg initial weight) for year 2. Years refer to year of experiment and not fish age class. There were no significant differences in total yield, dressed yield, or muscle fat, regardless of diet or feeding regimen within year. Year-one fish (study 2) fed to satiation tended to gain more weight and appeared to convert feed better than fish fed at a restricted rate. In study 2 there were significant interactions between year and feed, and between year and feeding regimen. Percentage visceral fat was reduced by feeding a high-protein feed during year 1 (study 1). Females also generally had a higher percentage visceral fat than males, regardless of diet. Year-two-fish generally contained a higher percentage of visceral fat as compared to year-one fish. In study 2, there was a significant interaction effect between year, feed, feeding regimen, and sex on visceral fat. Increasing dietary protein or restricting feed appeared to have only marginal effects on fattiness in channel catfish. Fish size and/or age appeared to influence fattiness more than diet or feeding regimen.     

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.     

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.     

The Effects of Water Velocity on the Growth,Dressout, and Body Composition of Channel Catfish,Ictalurus punctatus,Raised in Cicular Tanks

Research was conducted to determine the influence of water velocity on growth, dressout characteristics and fillet proximate composition of channel catfish, Ictalurus punctatus, raised in circular tanks. In this study, channel catfish cultured in water velocities of 4 cm/second averaged 75 g/fish higher weight gain and 0.12%/day greater specific growth rates than channel catfish cultured in tanks having no water velocity (P < 0.05). Channel catfish cultured at water velocities of 4 cm/second had significantly higher (P < 0.05) feed conversion efficiency and condition factor than channel catfish cultured in tanks having no water velocity. Channel catfish cultured at water velocities of 4 cm/second had significantly higher (P < 0.05) percentage carcass weight, fillet weight, and fillet moisture. The percentage visceral and fillet fat of channel catfish cultured at 4 cm/second was significantly lower (P < 0.05) than that for channel catfish raised in tanks having no water velocity. These results indicate that when cultured from initial weights of approximately 100 g to final weights exceeding 454 g in an environment having a water velocity of 4 cm/second, channel catfish have greater growth, dressout and lower fat levels than channel catfish produced in tanks having the identical water exchange rates but no water velocity.     

Folic Acid and Pteroic Acid Related to Anemia of Cultured Channel Catfish,Ictalurus punctatus

The objective of this study was to analyze channel catfish feeds for folic acid and pteroic acid concentrations and correlate these substances with anemia in channel catfish, Ictalurus puncratus. From 1983 to 1987, feed-related anemia was diagnosed 298 times in cultured channel catfish in Alabama. Analysis of eight brands of anemia-associated feeds (AAF) and nonanemia-associated feeds (NAAF) suggested that AAF were either lower in folic acid or were higher in pteroic acid concentrations than the NAAF. AAF contained a folic acid: pteroic acid ratio of less than 1.8:1, compared to a folic acid:pteroic acid ratio of greater than 10:1 in NAAF. Low folic acid concentrations were due either to insufficient addition at the feed mill or due to degradation during storage.     

Effects of Fasting on Fatty Acid Composition of Muscle, Liver, and Abdominal Fat in Channel Catfish Ictalurus punctatus

Channel catfish Zctalurus punetatus were fasted for 20, 40, 60, and 80 d. Proximate and fatty acid composition of liver, abdominal fat, muscle, and viscera were determined. Percentage moisture, protein, and lipid of viscera showed little change during the period of fasting. Percentage protein in muscle decreased ( P < 0.05) after 20 d of fasting from time 0 (control), while percentage lipid increased ( P < 0.05). Fish fasted for 0, 40, 60, and 80 d were not different ( P > 0.05). In the liver, percentage lipid was higher in fish that were not fasted (0 d) than in fish fasted 20, 40, 60, and 80 d ( P < 0.05). while percentage moisture was lower in control fish compared to all other treatments ( P < 0.05). Fatty acid composition of muscle and liver indicated that docosahexaenoic acid (DHA), 22:6(n-3), was conserved in these tissues during fasting, while oleic acid, 18:1(n-9), concentration decreased during fasting. Fatty acid composition of abdominal fat indicated that a high percentage (>50%) of the total lipid was composed of oleic acid and there was little change in levels of individual fatty acids in abdominal fat during 80 d of fasting.     

外源核苷酸对斑点叉尾(鱼回)生长及肠道组织发育的影响

以斑点叉尾(鱼回)幼鱼为试验对象,研究不同水平外源核苷酸对其生长和肠道发育的影响.在基础饲料中分别添加0.0%(对照组)、0.02%、0.05%和0.1%的外源核苷酸.结果表明,在斑点叉尾(鱼回)幼鱼日粮中添加外源核苷酸,促生长作用不显著(P>0.05),但可显著促进肠道组织的发育(P<0.05).     

Validation of a Time-Resolved Fluoroimmunoassay for Measuring Plasma Cortisol in Channel Catfish Ictalurus punctatus

Abstract.— A time-resolved fluoroimmunoassay (TR-FIA) marketed for measuring cortisol in human sera was evaluated and validated for use in the quantification of plasma cortisol concentrations of channel catfish Ictalurus punctatus . Time-resolved fluoroim-munoassays provide non-isotopic alternatives to the use of radioimmunoassays (RIA). The evaluated TR-FIA satisfied strict criteria of precision (intra-assay coefficients of variation (CV) < 7%) and reproducibility (inter-assay CV ≤ 9%). Accuracy of the TR-FIA, calculated as the percent of exogenous cortisol recovered from spiked catfish plasma, averaged 99.5%. Assay sensitivity (minimum detection limit) in catfish plasma was 1.2 ng/mL, and the displacement curve for serially diluted channel catfish plasma paralleled the cortisol standard curve. Plasma cortisol concentrations of channel catfish in the presence and absence of a confinement stressor were used to characterize the im-munoreactive cortisol measurable by TR-FIA, and compared favorably to RIA values for the same samples ( r ² = 0.95, P < 0.001).     

Evaluation of Practical Diets with Various Levels of Dietary Protein and Animal Protein for Pond-Raised Channel Catfish Ictalurus punctatus1

Three levels of dietary protein (26, 28, or 32%) and four levels of animal protein (0, 2, 4, or 6%) were evaluated in a factorial experiment for pond-raised channel caffish using practical-type extruded feeds. Meat, bone, and blood meal (65% protein) was used as the animal protein source. Channel catfish fingerlings (average weight: 69 glfish) were stocked into 48 0.04-ha ponds at a rate of 24,700 fishha. Four ponds were used for each dietary treatment. Fish were fed once daily to apparent satiation for 158 d. No differences were observed in weight gain, feed consumption, feed conversion ratio, survival, and hematocrits of channel catfish fed diets containing various levels of dietary protein and animal protein. Inclusion of animal protein in the diet did not affect fish dressout, percentage visceral fat, or fillet composition. Comparison of means pooled by dietary protein without regard to animal protein showed that fish fed diets containing 26% protein had a lower percentage dressout than fish fed higher protein diets (55.4% vs. 56.3%). Fish fed the 32% protein diet had lower visceral fat than those fed the 26% or 28% protein diet (2.9% vs. 3.6% or 3.4%). Fillet fat was lower for fish fed the 32% protein diet than for fish fed the 26% protein diet (5.8% vs. 7.1%). Fillet fat in fish fed the 28% protein diet (6.5%) was not different from fish fed either 26% or 32% dietary protein. No differences were detected in fillet protein, moisture, and ash concentrations among fish fed diets containing various concentrations of protein. There were no interactions between dietary protein and animal protein for any variables. Results from the present study indicate that animal protein can be eliminated from diets for grow out of channel catfish fed to apparent satiation using diets containing 26% to 32% crude protein.     

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.     

Growth Performance and Proximate and Fatty Acid Compositions of Channel Catfish, Ictalurus punctatus, Fed for Different Duration with a Commercial Diet Supplemented with Various Levels of Menhaden Fish Oil

A 15‐wk study was conducted to evaluate the effect of supplemental menhaden fish oil levels and feeding duration on growth performance and tissue proximate and fatty acid (FA) compositions of juvenile channel catfish, Ictalurus punctatus. Dietary fish oil levels had no effect on final weight gain, feed efficiency, and survival of channel catfish. Tissue lipid contents were directly correlated to dietary lipid levels, while moisture contents were inversely related to dietary lipid levels. Fillet moisture contents progressively decreased, whereas fillet lipid increased with increasing feeding duration. Significant increase in saturated and total n‐3 FAs and decrease in monoenoic and total n‐6 FA in whole body and fillet were observed at each incremental level of dietary fish oil. Percentages of n‐3 and n‐3 highly unsaturated fatty acids in fillet of fish fed the control and 3% fish oil diets decreased with increasing feeding periods, whereas those of fish fed 6 or 9% added fish oil diets remained stable or increased. Ratios of n‐3/n‐6 were statistically comparable throughout the 15‐wk feeding. When expressed in terms of mg/g of fillet, the highest concentration of n‐3 was obtained in fillets of fish fed the 9% added fish oil diet for 15 wk.     

Application of Compensatory Growth to Enhance Production in Channel Catfish Ictalurus punctatus

Four treatment groups that received repeating cycles of fixed feed deprivation for either 0, 1, 2, or 3 d (control, treatment 1, treatment 2, and treatment 3, respectively), followed by periods of refeeding with a 36% protein commercial catfish feed once daily as long as the active phase of compensatory growth (CG) persisted, were assessed in flow-through aquaria. No-feed periods elicited the CG state and were immediately followed by days of ad libatum refeeding. At the end of 10 wk, average growth rate (AGR) of fish was higher ( P < 0.05) than the control by 40%, 180%, and 191% for treatment 1, treatment 2, and treatment 3, respectively. The average weight of fish in treatment 3 was heavier ( P < 0.05) than the average control group at the end of the study period. Mean daily feed consumption was 3.91%, 5.03%, 5.36%, and 5.98% for control, treatment 1, treatment 2, and treatment 3, respectively. Mean feed consumption per fish per day was 24%, 71.3%, and 70.7% higher than the control in treatment 1, treatment 2, and treatment 3, respectively. Restricted feeding is one of the effective methods to contain ESC-related losses in commercial channel catfish fingerling operations. The mean cumulative survival of treatment groups registered higher ( P < 0.05) survival to Edwardsiella ictaluri infection compared to the daily fed control fish. Results from this study show that compensatory growth response triggered by periodic non-feeding days can improve growth rate, feed consumption, and improved survival to ESC infections in channel catfish fingerlings.