Library

Notes: Abstract.— Growth, histological lesions, and biochemical changes were investigated in channel catfish Ictalurus punctatus fed various concentrations of moniliformin with or without fumonisin B1. Channel catfish (average initial weight, 1.5 g) were fed diets formulated to contain 0, 20, 40, 60, and 120 mg moniliformin/kg; 0, 20, and 40 mg fumonisin B1/kg, or two combinations of moniliformin and fumonisin B1 for 10 wk. Fish fed diets with the lowest concentration of moniliformin or fumonisin B1 (20 mg/kg diet) had significantly (P 〈 0.05) less weight gain than the control fish. Increasing the level of moniliformin in the diets resulted in a linear decrease in weight gain. Overall mortality of fish was 4% and not related to treatment effects. Hematocrit was significantly (P 〈 0.05) lowered by 60-mg moniliformin/kg diet or 40-mg fumonisin B1/kg diet. Dose-dependent increases in serum pyruvate concentration and ratio of free sphinganine to free sphingonine were obtained with increasing concentration of dietary moniliformin and fumonisin B1, respectively. Mean serum pyruvate level was significantly (P 〈 0.05) higher in fish fed the diet containing 60-mg moniliformin/kg diet. Addition of fumonisin B1 (40 mg/kg) to the diet containing 40-mg moniliformin/kg significantly increased the serum pyruvate level above that of the control. Also, the lowest concentration of fumonisin B1 (20 mg/kg diet) significantly (P 〈 0.05) increased the ratio of sphingolipids. Combinations of moniliformin and fumonisin B1 at levels of 20:40 and 40:40 mg/kg diet did not significantly change the effect of fumonisin B1 on the ratio of sphingolipids. The only tissue lesions observed in liver and heart were smaller nuclei of cells in livers of fish fed diets containing the two highest levels of moniliformin and the combinations of the two toxins.

Notes: A laboratory study was conducted to evaluate effects of dietary total protein and animal protein source and concentration on growth and feed efficiency of juvenile channel catfish Ictalurus punctutus and their response to Edwardsiellu ictuluri challenge. Eight diets evaluated were: three diets containing either 28, 32, or 36% crude protein with 6% menhaden fish meal and 6% meat and bonehlood meal and five diets containing 32% crude protein with either no animal protein, 68 or 12% menhaden fish meal, or 6% or 12% meat and bonehlood meal, respectively. Twenty channel catfish with an average weight of 6.6 g/fish were stocked into each of forty 110-L flow-through aquaria (five aquaridtreatment). Fish were fed to approximate satiation twice daily for 9 wk. Fish in each tank were then exposed to E. ictaluri. There were no differences in feed consumption, weight gain, feed efficiency, and survival before and after challenge among fish fed diets containing 28, 32, or 36% protein with 6% menhaden fish meal and 6% meat and bone/ blood meal. Fish fed a 32% all-plant protein diet had weight gain and feed efficiency similar to fish fed diets containing 12% menhaden fish meal, but had a higher weight gain than fish fed a 32% protein diet containing 6% meat and bonehlood meal. No significant differences were observed in survival after E. ictuluri challenge among fish fed diets containing the various levels of animal proteins. Results indicate that dietary protein levels varying from 28% to 36% do not appear to affect growth, feed efficiency. and E. icraluri resistance or susceptibility in fingerling channel cattish fed to satiation and raised from approximately 7 to 56 g under laboratory conditions. Data also demonstrate that a 32% all-plant protein diet can be fed to small fingerling channel catfish without adversely affecting growth, feed efficiency, or resistance to E. ictuluri.

Notes: 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.

Notes: 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.

Notes: 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.

Notes: A 2 ± 4 factorial experiment was conducted to examine effects of dietary protein level (28, 32, 36, and 40%) and feeding rate (satiation or ± 90 kg/ha per d) on production characteristics, processing yield, body composition, and water quality for pond-raised channel catfish Ictalurus punctatus. Fingerling channel catfish with a mean weight of 64 g/fish were stocked into 40 0.04-ha ponds at a rate of 17,290 fish/ha. Fish were fed once daily to apparent satiation or at a rate of ± 90 kg/ha per d for 134 d during the growing season. Dietary protein concentration had no effect on feed consumption, weight gain, feed conversion, survival, aeration time, or on fillet moisture, protein, and fat levels. Fish fed to satiation consumed more feed, gained more weight, had a higher feed conversion, and required more aeration time than fish fed a restricted ration. Visceral fat decreased, and fillet yield increased as dietary protein concentration increased to 36%. Carcass yield was lower for fish fed a diet containing 28% protein. Increasing feeding rate increased visceral fat but had no major effect on carcass, fillet, and nugget yields. Fish fed to satiation contained less moisture and more fat in the fillets that those fed a restricted ration. Nitrogenous waste compounds were generally higher where the fish were fed the higher protein diets. Although there was a significant interaction in pond water chemical oxygen demand between dietary protein and feeding rate, generally ponds in the satiation feeding group had higher chemical oxygen demand than ponds in the restricted feeding group. There was a trend that pond water total phosphorus levels were slightly elevated in the satiation feeding group compared to the restricted feeding group. However, pond water soluble reactive phosphorus and chlorophyll-a were not affected by either diet or feeding rate. Results from the present study indicate that a 28% protein diet provides the same level of channel catfish production as a 40% protein diet even when diet is restricted to 90 kg/ha per d. Although there was an increase in nitrogenous wastes in ponds where fish were fed high protein diets, there was little effect on fish production. The long term effects of using high protein diets on water quality are still unclear. Feeding to less than satiety may be beneficial in improving feed efficiency and water quality.

Notes: Abstract.— This study evaluated the effects of dietary protein concentration (26, 28, and 32%) on growth. feed efficiency, processing yield, and body composition of USDA103 and Mississippi “normal” (MN) strains of channel catfish raised in ponds. Fin-gerling channel catfish (average weight = 32.5 and 47.3 g/fish for USDA103 and MN strains, respectively) were stocked into 24 0.04-ha ponds (12 ponds/ strain) at a density of 18,530 fish/ha. Fish were fed once daily to apparent satiation from May to October 1999. There were no interactions between fish strain and dietary protein concentration for any parameters measured. Regardless of dietary protein concentrations, the USDA103 strain consumed more feed and gained more weight than the MN strain. There were no differences in feed conversion ratio (FCR) or survival between the two strains. Feed consumption, weight gain, FCR, and survival were not affected by dietary protein concentration. The USDA103 strain exhibited a lower level of visceral fat, a higher carcass yield, a lower level of fillet moisture, and a higher level of fillet fat than the MN strain. Regardless of fish strains, fish fed the 32% protein diet had a lower level of visceral fat and a higher fillet yield than fish fed the 26% protein diet. Fish fed the 32% protein diet were also higher in carcass yield as compared to those fed the 28% protein diet. Fillet moisture, protein, and fat concentrations were not affected by dietary protein concentration. Results from this study indicate that the USDA103 strain of channel catfish appears to possess superior traits in growth characteristics compared with the MN strain that is currently cultured commercially. Both strains appear to have the same dietary protein requirement.

Notes: Aflatoxins are a group of mycotoxins produced by the mold organisms Aspergillus flavus and A. parasiticus on feed grains and oil seeds such as corn, peanuts, and cottonseed. Research conducted in aquaria, about 15 yr ago, demonstrated that channel catfish Ictalurus punctatus are very tolerant to dietary aflatoxin B1 (AFB1) from a purified source. To evaluate the effect of feeding diets containing aflatoxin from a natural source, moldy corn (MC) naturally contaminated with a high concentration (550 pg/kg) of total aflatoxins was incorporated into practical diets. The diets were fed to Juvenile catfish in two experiments. Experiment 1 consisted of feeding catfish (mean body weight 7.1 g/fish) four diets containing 20% or 40% of two lots of corn; one with no apparent mold contamination, which was designated as clean corn (CC), or the previously described MC. Each diet was fed twice daily to five 100-L aquaria of 20 fish each for 12 wk. Experiment 2 consisted of three diets containing either 50% CC or MC, or a combination of 25% CC and 25% MC prepared by the cooker-extrusion method. Each diet was fed once daily for 130 d to five replicate 0.04-ha ponds of catfish fingerlings. Results of these experiments indicate that feeding diets containing aflatoxin from moldy corn does not affect channel catfish weight gain, feed consumption, feed efficiency, survival, hematocrit, or hepatosomatic ratio. No liver abnormalities were observed upon gross examination. Levels of aflatoxin were reduced approximately 63% in the diets used in experiment 2 after exposure to the high temperature (ca. 120 C) of the cooker-extrusion process used to manufacture commercial catfish diets.