Evaluation of Various Concentrations of Dietary Protein and Animal Protein for Pond-Raised Channel Catfish Ictalurus punctatus Fed to Satiation or at a Restricted Rate

A factorial experiment was conducted to evaluate effect of dietary protein (28% or 32%), animal protein (0, 3, or 6%), and feeding rate (satiation or >90 kg/ha per d) on production characteristics, processing yield, and body composition of pond-raised channel catfish Ictalurus punctatus . Fingerling channel catfish (average weight: 55 g/fish) were stocked into 60, 0.04-ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed once daily to satiation or no more than 90 kg/ha per d for 147 d. Fish fed at a rate of >90 kg/ha per d consumed about 85% of the amount of feed consumed by fish fed to satiation. Dietary protein did not affect the total amount of feed fed, amount of feed consumed per fish, weight gain, feed conversion efficiency, or fillet protein. Animal protein had no effect on the total amount of feed fed, amount of feed consumed per fish, weight gain, or fillet protein and ash. Fish fed a diet containing 6% animal protein converted feed more efficiently than fish fed diets containing 0% and 3% animal protein. Fish fed to satiation daily consumed more feed, gained more weight, converted the feed less efficiently, and had a higher carcass yield, a higher level of visceral fat as compared to fish fed at a rate of >90 kg/ha per d. Feeding rate had no effect on fillet protein. Results from this study indicated that both a 28% and a 32% protein diet with or without animal protein provided the same growth rate of channel catfish raised in ponds from fingerlings to marketable size if feed is not restricted below a maximum rate of 90 kg/ha per d. Even though there were some interactions among the three factors evaluated, dietary protein levels of 28% to 32% and animal protein levels of 0% to 6% do not appear to markedly affect carcass yield and fillet proximate composition of pond-raised channel catfish.     

Comparison of Practical Diets with and without Animal Protein at Various Concentrations of Dietary Protein on Performance of Channel Catfish Ictalurus punctatus Raised in Earthen Ponds1

Abstract— A 2 × 5 factorial experiment was conducted using practical-type extruded feeds containing 20, 24, 28, 32, or 36% crude protein with or without animal protein. The animal protein supplement consisted of 4% menhaden fish meal and 4% meat, bone and blood meal. Channel catfish fingerlings (average size: 26.3 g/fish) were stocked into 50 0.04-ha ponds at a rate of 24,700 fishha. Five ponds were used for each dietary treatment. Fish were fed once daily to satiation for 202 d. There were no differences in feed conversion ratio (FCR), percentage fillet moisture, and survival among treatments. In fish fed diets containing no animal protein, feed consumption, weight gain, and percentage dressout were lower for fish fed the 20% protein diet than those fed diets containing 28% and 32% protein. Fish fed 28, 32, or 36% protein diets without animal protein did not differ in respect to percentage dressout and percentage visceral fat; fish fed the 36% protein diet had higher percentage fillet protein and a lower percentage fillet fat than fish fed other diets with the exception of fish fed the 28% protein diet. In fish fed diets containing animal protein, feed consumption, weight gain, percentage fillet protein and ash, and percentage dressout were lower and visceral fat was higher for fish fed the 20% protein diet than those fed other diets. Fish fed diets containing 24% protein and above with animal protein were not different in respect to weight gain and feed consumption, but fish fed the 24% protein diet had a higher percentage fillet fat than fish fed a 32% or 36% protein diet. Fish fed the 32% protein diet had a lower visceral fat. Considering animal protein vs non-animal protein with the data pooled across all diets without regard to dietary protein level, weight gain and FCR of fish fed diets containing animal protein were higher than those fed diets containing no animal protein. However, weight gain of fish fed diets containing 20, 28, or 32% protein with or without animal protein did not differ. Dressout percentage and fillet protein were higher and fillet fat was lower for fish fed diets containing no animal protein than those fed diets containing animal protein. Data from this study indicated that animal protein may not be a necessary dietary ingredient for fish fed 28% or 32% protein diets typically used for grow out of pond-raised channel catfish under satiation feeding conditions. Whether animal protein should be included in catfish diets containing less than 28% protein is unclear, since fish fed the 24% protein diet benefited from animal protein but those fed the 20% protein diet did not benefit from animal protein. Additional studies to provide more information on low-protein, all-plant diets are currently being conducted.     

Evaluation of Corn Gluten Feed as a Dietary Ingredient for Pond-Raised Channel Catfish Ictalurus punctatus

Abstract.— This study was conducted to evaluate corn gluten feed as an alternative feedstuff in the diet of pond-raised channel catfish Ictalurus punctatus . Three 32%-protein diets containing 0%, 25%, or 50% corn gluten feed were tested. Channel catfish fingerlings (average weight: 57 g/fish) were stocked into 15 0.04-ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed to satiation once daily for a 147-d growing period. No differences were observed in feed consumption, weight gain, feed conversion ratio, survival, or fillet protein concentration among fish fed the test diets. Fish fed diets containing 25% and 50% corn gluten feed exhibited a lower level of visceral fat and a higher carcass yield than fish fed the control diet without corn gluten feed. The diet containing 50% corn gluten feed resulted in a lower level of fillet fat and a higher level of moisture than the control diet. There were no visible differences in the coloration of skin or fillet of channel catfish fed diets with and without corn gluten feed. Results from this study indicated that channel catfish can efficiently utilize corn gluten feed at levels up to 50%n without adverse effect on feed palatability, weight gain, or feed efficiency. Corn gluten feed may be beneficial in reducing fattiness of channel catfish and improving carcass yield by reducing the digestible energy to protein ratio of the diet.     

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.     

Production Characteristics of Pond-Raised Channel Catfish Ictalurus punctutus Fed Diets With and Without Animal Protein for Three Growing Seasons1

An experiment was conducted to determlne the long-term effects of an all-plant-protein diet on production characteristics (harvest yield, dressing percentage, and body composition) of catfish Ictalurus punctatus taken from top-harvested, multiple-stocked ponds over a 2.5-yr period of continuous production. Fish in eight 0.08-ha ponds were fed an extruded, 32% protein control diet (CON) containing animal and plant proteins, while fish in eight replicate ponds were fed an isonitrogenous diet containing only plant proteins, primarily from cottonseed meal and soybean meal (APP). Diets were fed once dally to apparent satiation during the growing season. Ponds were top-harvested twice per year in the spring and fall and partially restocked after each harvest. CON-fed fish received 13,335 kg of feed during the 2.5-yr period. APP-fed fish received 13,506 kg of feed. Total yields were 5,562 kg of CON-fed fish and 5,840 kg of APP-fed fish; average annual yields were 3,477 kgha per yr and 3,650 kgha per yr, respectively (P > 0.05). Feed conversion ratios, 2.5 for CON-fed fish and 2.6 for APP-fed Ash, did not differ significantly (P > 0.05). Live weights at harvest averaged 529 g (CON) and 481 g (APP), and were not significantly different. Dressing percentages were 59% for fish fed both diets (P > 0.05). APP-fed fish had less (P < 0.05) visceral fat and less (P < 0.05) muscle lipid than CON-fed fish. Results indicate that a lysine supplemented, all-plant-protein diet containing 40% cottonseed meal and 20% soybean meal is suitable for long-term production of channel catfish in earthen ponds and such a diet can reduce the fat content of pond-reared fish.     

Comparison of Channel Catfish,Ictalurus punctatus,and Blue Catfish,Ictalurus furcatus,Fed Diets Containing Various Levels of Protein in Production Ponds

A comparative study was conducted on growth and protein requirements of channel catfish, Ictalurus punctatus, and blue catfish, Ictalurus furcatus. Four diets containing 24, 28, 32, or 36% protein were fed to both channel (initial weight 6.9 g/fish) and blue (6.6 g/fish) catfish for two growing seasons. There were significant interactions between dietary protein and fish species for weight gain and feed conversion ratio (FCR). No significant differences were observed in weight gain of channel catfish fed various protein diets, whereas higher protein diets (32 and 36%) resulted in better weight gain in blue catfish than lower protein diets (24 and 28%). No consistent differences were observed in the FCR of channel catfish fed various levels of dietary protein, whereas significantly higher FCRs were noted in blue catfish fed the 24 and 28% protein diets compared with fish fed 32 and 36% protein diets. Regardless of dietary protein levels, blue catfish had higher carcass, nugget, and total meat yield, and higher fillet moisture and protein, but lower fillet yield and fillet fat. Regardless of fish species, fish fed the 36% protein diet had higher carcass, fillet, and total meat yield than fish fed the 28 and 32% protein diets, which in turn had higher yields than fish fed the 24% protein diet. It appears that blue catfish can be successfully cultured by feeding a 32% protein diet.     

Evaluation of Coastal Bermuda Grass Protein Isolate as a Substitute for Fishmeal in Practical Diets for Channel Catfish Ictalurus punctatus

In response to concerns over availability and cost of fishmeal for aquaculture feeds, a study was conducted to evaluate the suitability of a protein isolate from coastal Bermuda grass Cynodon dactylon for channel catfish Ictalurus punctatus . The coastal Bermuda grass was treated by soaking in liquid anhydrous ammonia under high pressure at 70 C, a process known as Ammonia Fiber Explosion (AFEX), followed by pressure release, extraction and isoelectric precipitation for isolation of the protein. Amino acid analysis of the isolate (32% crude protein) indicated a generally balanced profile that was first limiting in methionine. A feeding trial was conducted in which four isonitrogenous and isocaloric diets containing incremental levels of the extracted, isolated protein were evaluated. The control diet contained 10% menhaden fishmeal and experimental diets were formulated so that the isolate replaced 33, 66 and 100% of the fishmeal on an equal-protein basis. Each diet was fed for 9 wk to triplicate groups of channel catfish fingerlings initially weighing approximately 14 g/fish. Apparent protein and organic matter digestibility of the isolate also was determined utilizing chromic oxide as an inert marker. Results of the feeding trial indicated that substitution of the isolate at all levels did not significantly ( P > 0.05) affect weight gain, feed efficiency, protein efficiency ratio or protein retention of channel catfish. Apparent protein and organic matter digestibility coeflicients of the isolate were 85 and 89%, respectively. These data indicate that the isolate was readily digested by channel catfish and was able to replace menhaden fishmeal (at 10% of diet) without adversely affecting fish performance. Additional research to evaluate substitution of other ingredients with the protein isolate appear warranted. Further research to optimize protein isolation procedures also is required.     

Low-Quality Diets for Growout of Channel Catfish,Ictalurus punctatus

Abstract

A feeding trial was conducted to evaluate low-quality diets for growout of pond-raised channel catfish. Five practical diets containing various levels of protein (10-28%) of varying quality (with or without animal protein and/or soybean meal), and with or without certain nutrient supplements (vitamin, minerals, lysine, or fat) were fed to channel catfish, Ictalurus punctatusstocked in 0.04-ha earthen ponds at a rate of 17,290 fish/ha. The diets were as follows: (1) 28% protein, nutritionally complete control; (2) 28% protein without supplemental vitamins, minerals, or fat; (3) 18% protein + supplemental lysine, vitamins, and minerals, but without animal protein; (4) 10% protein without animal protein, soybean meal, or supplemental vitamins and minerals; and (5) 10% protein + supplemental lysine, vitamins, and minerals, but without animal protein or soybean meal. Each diet was fed once daily to apparent satiation to fish in five replicate ponds for a single growing season. Fish fed diets containing 18% or 28% protein without supplements had similar diet consumption rates and weight gain as those fed the 28% control diet, but the fish fed the control diet converted diet more efficiently. Fish fed the 10% protein diet without supplements consumed less diet, converted diet less efficiently, and gained less weight than fish fed diets containing higher levels of protein. The addition of supplements to the 10% protein diet increased weight gain and processing yield as compared to fish fed the 10% protein diet without supplements. Body fattiness increased, fillet protein decreased, and carcass, fillet and nugget yields decreased as dietary protein decreased. The data show that pond-raised channel catfish can be grown effectively on a diet containing 18% protein that is of relatively low quality, but fattiness is increased and processing yield is decreased. However, because of the negative aspects of this diet, we would not recommend it for general use in commercial catfish culture. It could be used where fattiness and processing yield are not of consequence, such as recreational ponds. For that matter, the 10% diet without supplements could be used as well in these situations if maximum growth is not desired.     

Low Protein Diets for Channel Catfish Ictalurus punctatus Raised in Earthen Ponds at High Density1

This study was conducted to evaluate the use of low protein diets for channel catfish Ictalurus punctatus raised in earthen ponds at high density. Fingerling channel catfish were stocked into 0.04-ha earthen ponds at a rate 24,700 fish/ha and fed experimental diets daily to satiation from April to October 1995. The five diets contained either 32, 28, 24, 20, or 16% crude protein with digestible energy to protein (DE:P) ratios ranging from 8.9 to 16.2 kcal/ g protein. Weight gain was not different among channel catfish fed diets containing 32, 28, or 24% crude protein. Fish fed diets containing 20% or 16% crude protein gained less weight than fish fed the diets containing 28% or 24% crude protein, but not statistically less than the fish fed the 32% crude protein diet. Feed consumption data followed similar trends as weight gain data. Feed conversion ratio increased linearly as dietary protein decreased, but was not significantly different (multiple range test) for fish fed diets containing either 32% or 28% crude protein. There were no differences in survival and hematocrit of fish fed the different diets. No differences (multiple range test) were observed in dressout percentages for fish fed the various diets, but dressout percentage tended to decrease linearly as dietary protein decreased. Visceral fat and fillet fat increased and fillet protein and moisture decreased linearly as dietary protein decreased. Results from this study indicated that dietary protein concentrations as low as 24% are adequate for maximum weight gain of pond-raised channel catfish fed daily to satiation. Fish fed dietary protein levels below 24% grew relatively well, particularly considering that dietary protein was reduced 40–50% below that typically used in commercial channel catfish feeds. However, dietary protein levels below 24% may increase fattiness to an unacceptable level presumably because of the high digestible energy to protein ratio.     

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.     

Evaluation of Three Strains of Channel Catfish Ictalurus punctatus Fed Diets Containing Three Concentrations of Protein and Digestible Energy1

Abstract A 3 × 3 factorial experiment was conducted using three strains of channel catfish Ictalurus punctatus, USDA102, USDA103, and Mississippi normal (MN), and three concentrations of dietary protein. Three practical diets were formulated to contain 25, 35, or 45% crude protein with digestible energy/protein ratio of 10.0, 8.1, or 6.8 Kcal/g, respectively. Juvenile channel catfish (mean initial weight: 15.1 g/fish) were fed the experimental diets twice daily to approximate satiation for 8 wk. Regardless of dietary protein concentration, the USDA 103 strain consumed more feed, gained more weight, and converted feed more efficiently than other two strains. The MN strain consumed less feed and gained less weight than the other strains. Regardless of the strain of channel catfish, differences in weight gain, feed consumption, and feed conversion ratio were observed among fish fed diets containing various levels of protein with the 35% protein diet being the best. Neither dietary protein concentration nor strain had significant effect on fillet protein level. Data pooled by fish strain showed that fish of MN strain had lower fillet fat and higher moisture than fish of other two strains. Data pooled by dietary protein showed that fish fed the 45% protein diet had a lower level of fillet fat than fish fed the 35% protein diet, but this did not appear to be a strain effect, rather it was a result of decreased feed consumption. Results from this study clearly demonstrate that per formance of the USDA103 strain of channel catfish was superior to other strains tested. The growth characteristics of the USDA103 strain of channel catfish make the strain a promising candidate for commercialization. However, data are needed on performance of the strain from fingerling to marketable size under conditions similar to those used for the commercial culture of channel catfish prior to their release to the catfish industry.     

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.     

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.     

Microbial Phytase Can Replace Inorganic Phosphorus Supplements in Channel Catfish Ictalurus punctatus Diets1

Abstract.– Juvenile channel catfish Ictalurus punctatus (initial weight: 6.8 g/fish) were fed four practical diets containing 0, 250, 500, and 750 units of microbial phytase/kg and a diet containing 1% feed grade dicalcium phosphate (but no microbial phytase) under laboratory conditions for 12 wk. Fish fed the diets containing 250 units of microbial phytase/kg and above consumed more feed, gained more weight, and had a lower feed conversion ratio (FCR) in comparison to fish fed the basal diet containing no microbial phytase. Fish fed the diet containing dicalcium phosphate had intermediate weight gain and feed conversion ratio as compared to fish fed the basal diet and diets containing microbial phytase. Bone ash and phosphorus concentrations were lower for fish fed the basal diet than for fish fed other diets. No differences in weight gain, feed consumption, FCR, bone ash and bone phosphorus were observed among fish fed the diets containing various levels of microbial phytase. Fish fed the diet containing dicalcium phosphate had a lower bone phosphorus concentration than fish fed diets containing microbial phytase. Fecal phosphorus concentrations were lower for fish fed the diets containing microbial phytase than for fish fed the basal diet and the diet containing dicalcium phosphate. Results from the present study indicated that addition of 250 units of microbial phytase/kg to practical diets can effectively improve bioavailability of phytate phosphorus to channel catfish and may possibly eliminate the use of an inorganic phosphorus supplement in channel catfish diets. However, these data must be verified in trials conducted in ponds, prior to recommending removal of supplemental phosphorus from channel catfish diets.     

Substitution of Canola Meal for Soybean Meal in Diets for Channel Catfish Ictalurus punctatus

Abstract Canola meal was used in channel catfish Ictalurus punctatus diets at levels of 0, 15.4, 30.8, 46.2 and 61.6%, by progressively replacing (on an equal nitrogen basis) 0, 25, 50, 75, or 100% of solvent-extracted soybean meal in the control diet. The feeds were formulated to contain approximately 29% crude protein and 2,650 kcal of digestible energy/kg on an air-dry basis. Each diet was fed to juvenile channel catfish to satiation twice daily for 10 wk. Fish fed the diets containing the two lowest levels of canola meal (15.4 and 30.8%) had similar weight gains, feed intakes, feed utilization efficiencies, and percent survivals relative to the group fed the control diet. Weight gains and feed intakes declined significantly as the dietary levels of canola meal were increased to 46.2% or higher, probably because of reductions in diet palatability and some impairment of feed utilization due to the presence of increased levels of antinutritional factors, particularly glucosinolates. Whole body percentages for moisture and crude protein were unaffected by the dietary treatments. Body ash contents, however, were lowest for fish fed the control diets but were essentially the same for fish fed the other diets. Fish fed the diet containing 30.8% canola meal had lowest body fat content but this effect may not have been diet related. Values for red blood cell concentration, hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were not affected by dietary canola meal level, but hematocrit was higher (although not always significant) for fish fed the control diet. The results of this study suggest that canola meal can comprise about 31% of the diet of channel catfish by replacing half of the amount of soybean meal used in the control diet without adversely affecting growth or any other aspect of performance.     

Increasing Fish Oil Levels in Commercial Diets Influences Hematological and Immunological Responses of Channel Catfish,Ictalurus punctatus

Growth performance, immune responses and disease resistance were studied in juvenile channel catfish, Ictalurus punctatus, fed a commercial diet (35.3% crude protein and 5.6% lipid) supplemented with menhaden fish oil at levels of 0, 3, 6, and 9% for 15 wk. Dietary fish oil levels did not significantly influence growth performance of catfish. Fatty acid compositions of whole‐body and liver reflected dietary fatty acid composition. No differences were found in hematological values, except that fish fed the 9% fish oil diet had significantly lower hematocrit. The resistance of erythrocytes to hemolysis in hypotonic solutions increased with increasing fish oil levels and the highest resistance was seen with the 9% fish oil diet. Fish fed 6 and 9% added fish oil diets had significantly higher serum protein levels than that of control fish. Serum lysozyme activity of fish fed 3 and 6% added fish oil diet was significantly higher than that of the control. Complement activity and chemotaxis ratio significantly decreased in fish fed diets with 6 or 9% added fish oil. The 3% added fish oil diet, however, had significantly highest natural hemolytic complement activity. Mortality from Edwardsiella ictaluri 14 d postchallenge and antibody titers to E. ictaluri did not differ among treatments.     

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.     

Evaluation of Cuphea Meal as an Ingredient Replacement in Channel Catfish,Ictalurus punctatus,Diets

ABSTRACT

Cuphea meal is a new, alternative feedstuff that has potential as a sustainable, economical replacement for wheat, rice, and corn ingredients in channel catfish, Ictalurus punctatus, diets. Channel catfish fingerlings were fed a control diet containing wheat or two experimental diets containing 7.5% cuphea meal, or 12.5% cuphea meal for eight weeks to determine if cuphea meal could replace wheat products in catfish diets. Mean (±SE) weight gains were 317.8 ± 28.8 g, 407.0 ± 36.9 g, and 372.8 ± 29.8 g for fish fed the control diet, the 7.5% cuphea meal diet, and the 15% cuphea meal diet, respectively, and there were no significant differences (P < 0.05) among treatments. Mean (±SE) whole-body protein of fish fed the cuphea diets (13.3 ± 0.66 and 14.5 ± 0.21%) was significantly (P < 0.05) higher than that of fish fed the wheat diet (12.7 ± 0.44%). Cuphea meal enhanced body composition of juvenile channel catfish without affecting growth or survival. Therefore, cuphea meal is a promising candidate for replacement of wheat bran at the levels tested.     

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.     

Effects of Various Dietary Carotenoid Pigments on Fillet Appearance and Pigment Absorption in Channel Catfish, Ictalurus punctatus

A study was conducted to evaluate effects of various carotenoids on skin and fillet coloration and fillet carotenoid concentration in channel catfish, Ictalurus punctatus. For 12 wk, juvenile catfish were fed one of six experimental diets containing no supplemental carotenoid or 100 mg/kg of one of following carotenoid additions: β‐carotene (BCA), lutein (LUT), zeaxanthin (ZEA), canthaxanthin (CAN), and astaxanthin (AST). Visual yellow color intensity score was highest for fish fed LUT, followed by ZEA, AST, and CAN, and lowest for fish fed basal and BCA diets. Skin and tissue Commission Internationale de I’Eclairage yellowness value was the highest in fish fed LUT, followed by fish fed ZEA, AST, and CAN, and lowest for fish fed basal and BCA diets. Fish accumulated the supplemental carotenoids in muscle tissues, but concentrations of different carotenoids in the tissue varied greatly. Approximately 30% of the LUT added was converted to echineone; no conversion was observed among other supplemental carotenoids. Results from the present study indicate that channel catfish can accumulate yellow pigments LUT and ZEA and red or pink pigments CAN and AST in the flesh, resulting in yellow coloration. The yellow pigment BCA does not appear to deposit in skin or flesh at levels sufficient to alter the coloration.