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AbstractThe present study examined the use of hydrolyzed poultry feathers (HPF) as a replacement for soybean meal in diets for pond raised Channel Catfish Ictalurus punctatus. Four isonitrogenous (28% crude protein) diets were evaluated that contained 0, 5, 10, or 15% HPF. Fingerling Channel Catfish (mean ± SD initial weight was 47.5 ± 2.2 g) were stocked into twenty 0.04-ha earthen ponds at a rate of 14,830 fish/ha. Fish were fed once daily to apparent satiation for 140 d. No significant differences were observed for weight gain, feed conversion ratio (FCR), and survival among fish fed various levels of HPF. There were also no significant differences in net yield of fish fed diets containing 0, 5, and 10% HPF, but net yield of fish fed a diet containing 15% HPF was significantly lower than that of fish fed the control diet. Fish on diets containing 5% HPF and above were fed significantly less feed than fish fed the control diet. Regression analysis showed that total amount of diet fed, net yield, and weight gain decreased linearly as dietary HPF levels increased. Based on weight gain and net yield data, 5% HPF with supplemental lysine may be used in Channel Catfish diets without marked impact on fish growth performance. However, carcass and fillet yield were significantly reduced in fish fed diets containing 5% HPF and higher. Fillet protein generally decreased and fillet fat increased with increasing dietary HPF levels.Received July 18, 2012; accepted September 12, 2012

AbstractThe present study examined the effects of dietary fiber and digestible energy on the feed intake, growth, and feed efficiency of juvenile channel catfish Ictalurus punctatus. Fish with an initial weight of 9.8 ± 0.1 g/fish (mean ± SD) were stocked in 110-L flow-through aquariums and fed for 9 weeks with practical diets that contained graded levels of fiber supplied by corn bran. As total dietary fiber (TDF) increased, feed consumption and weight gain increased and then decreased, showing a quadratic response. Maximum feed consumption occurred at a TDF level of 27.0% (5.7% crude fiber, 19.1% neutral detergent fiber [NDF]). Channel catfish appear to have some ability to adapt to increased dietary fiber by increasing feed intake to satisfy their energy requirements. Maximum weight gain was achieved at a TDF level of 23.4% (5.0% crude fiber, 15.7% NDF), indicating that the presence of dietary fiber at certain levels is beneficial to the fish. The maximum tolerance level for TDF by channel catfish was estimated to be 32.1% (6.6% crude fiber, 24.9% NDF). Feed efficiency, hepatosomatic index, and body fat decreased linearly with increasing dietary fiber. The maximum fiber tolerance levels may be used as upper limits for fiber when formulating practical diets for catfish containing corn by-products.Received June 20, 2011; accepted August 18, 2011

AbstractThe present study examined the effects of various daily feeding rates and feeding every other day on the growth, net yield, feed conversion ratio, and size distribution of hybrid catfish (female channel catfish Ictalurus punctatus× male blue catfish I. furcatus) in production ponds. Hybrid catfish fingerlings (average size, 45 g) were stocked into 0.04-ha ponds at a density of 14,826 fish/ha. Initially, all fish were fed to apparent satiation until feed consumption reached predetermined levels. Thereafter, the daily feeding rates for fish in the restricted feeding group were no more than 112, 135, or 168 kg·ha−1·d−1. Fish in the every-other-day feeding group were fed to apparent satiation daily until they reached about 0.23 kg and every other day to satiation thereafter. The results from the present study show that feeding every other day significantly reduces the weight gain and net yield of hybrid catfish but improves the feed conversion ratio. Partial budget analysis indicates that feeding hybrid catfish every other day is not economical at recent feed and fish prices. There were no significant differences in net yield, weight gain, and percentage of market-size fish among fish fed daily at various rates. Fish fed daily at no more than 112 and 135 kg/ha had significantly lower feed conversion ratios than fish fed daily to satiation. Simple regression analysis indicates that the weight gain, net yield, feed conversion ratio, and percentage of market-size fish increased linearly as the total amount of feed fed increased in fish fed daily. The results also show that the feed restriction used in the present study does not affect the size distribution of hybrid catfish.Received May 31, 2011; accepted August 18, 2011

AbstractThe prices of soybean meal and corn—the two most commonly used, traditional feed ingredients in channel catfish diets—have increased dramatically in recent years. Using less-expensive alternative feed ingredients to partially replace soybean meal and corn would reduce feed cost. The present study evaluated the use of corn gluten feed and cottonseed meal, two promising alternative feedstuffs, as replacements for soybean meal and corn in diets for pond-raised channel catfish Ictalurus punctatus. Five isonitrogenous (28% crude protein) diets that used corn gluten feed and cottonseed meal (approximately 1:1 ratio) to replace 0, 25, 50, 75, or 100% of the soybean meal in the control diet were evaluated. The level of corn in the diet decreased as those of corn gluten feed and cottonseed meal increased. Stocker-size channel catfish (mean initial weight = 0.175 kg/fish) were stocked into twenty 0.05-ha earthen ponds at a rate of 14,830 fish/ha. Fish were fed once daily to apparent satiation over a growing season. Net yield, carcass and fillet yield, and fillet protein and fat levels decreased and the feed conversion ratio increased linearly as soybean meal replacement levels increased. These results demonstrate that a maximum of 50% of the soybean meal in channel catfish diets may be replaced (soybean meal was reduced from 51.4% to 25.7%) by a combination of corn gluten feed and cottonseed meal (up to 20% of each in the diet) without markedly affecting the physical quality of feed pellets, fish growth, processed yield, and body composition. The poor performance of diets containing high levels of corn gluten feed and cottonseed meal are probably a result of high fiber, low digestible energy, or both.Received June 1, 2010; accepted October 1, 2010

AbstractEnteric septicemia of catfish (ESC), caused by the bacterium Edwardsiella ictaluri, is the most significant bacterial disease affecting channel catfish Ictalurus punctatus. Withholding feed during outbreaks of ESC is a widely accepted industry practice used to control losses from the disease. Scientific evidence concerning the validity of the practice is contradictory. Two studies were conducted to further evaluate the survival of channel catfish fingerlings following variable periods of feed deprivation before and after exposure to E. ictaluriin controlled aquarium experiments. In the first study, feed was withheld for varying time periods before bacterial challenge. After bacterial challenge, feed was either withheld or fish were fed daily. The second study utilized fish fed daily or fish deprived of feed 7 d before bacterial challenge. Daily feeding was resumed 4, 48, and 96 h after fish were exposed to E. ictaluri. In both experiments, the prechallenge feed treatments did not affect mortality. In contrast, withholding feed after bacterial challenge reduced mortalities by 52% in experiment 1 and by 45% in experiment 2. The highest mortality was observed when fish were fed immediately after immersion exposure and the lowest when fish were completely denied feed or fed daily starting 96 h after challenge. This reduction in mortality occurred when the concentration of E. ictaluriin aquarium water was negligible. These data suggest that when E. ictaluriis present in the water, feeding fish increases mortality by enhancing oral exposure to the pathogen.

AbstractJuvenile National Warmwater Aquaculture Center 103 (NWAC103) and Norris strain channel catfish Ictalurus punctatus(from 32 and 29 full-sib families, respectively) were individually tagged and stocked into 0.04-ha ponds at 14,400 fish/ha. Four ponds each of NWAC103 and Norris strain fish were fed a 32% protein diet and four ponds of NWAC103 fish were fed a 22% protein diet to satiation once daily for 150–178 d. Fish were harvested, counted, sexed, and weighed. Fish larger than 0.40 kg were processed and measured for yield and composition of various body components. The NWAC103 strain fish were larger at stocking than Norris strain fish; however, none of the strain-diet combinations differed with respect to survival, feed conversion ratio, or percent weight gain. The NWAC103 strain fish fed the 32% protein diet were larger at harvest and had faster growth at unit size (a) than Norris strain fish. Norris and NWAC103 strain fish fed the 32% protein diet did not differ in body component yield or composition. The NWAC103 strain fish fed the 22% and 32% protein diets did not differ in growth, but NWAC103 strain fish fed the 22% protein diet had lower processing yield (carcass, total fillet, and shank fillet) and higher visceral fat and fillet fat than NWAC103 strain fish fed the 32% protein diet. Compared with females, males had higher stocking weight, harvest weight, a, percent weight gain, head yield, fillet moisture, and nugget yield but lower visceral yield, carcass yield, fillet yield, and fillet fat. Family within strain was a significant source of variation (accounting for 10-45% of total variation) for all traits except fillet protein. The NWAC103 family rankings for most traits were consistent across diets (correlations generally >0.70 among best linear unbiased predictor values across diets). These results suggest that there is potential for improving growth and processing yield traits through selective breeding and that the improvements achieved through selection would be realized on either of the diets used.

AbstractTo evaluate the effect of mycotoxins on the disease resistance of juvenile channel catfish Ictalurus punctatus, we conducted an experiment in aquaria under controlled environmental conditions. Catfish were fed a nutritionally complete semipurified diet containing two concentrations of either T-2 toxin (1.0 or 2.0 mg/kg diet) or ochratoxin A (OA; 2.0 or 4.0 mg/kg diet). Mycotoxins were supplied as pure, crystalline T-2 toxin diluted to a known concentration in a carrier of casein and Aspergillus ochraceusculture material containing a known concentration of OA. After 6 weeks of feeding, catfish were challenged by immersion in situ with a virulent isolate of Edwardsiella ictalurisuspended in nutrient broth that provided an estimated 2.25 × 106colony forming units per milliliter of water. At 21 d postchallenge, significantly (P< 0.05) greater mortalities occurred among catfish fed T-2 toxin, 1.0 or 2.0 mg/kg diet (84.11% and 99.30%, respectively) than among control fish. Fish fed the OA diet (4.0 mg/kg) also had significantly higher mortality (80.49%) than control-fed catfish, which experienced 68.28% mortality. Results indicate that juvenile channel catfish fed feedborne mycotoxins T-2 toxin or OA had significantly greater mortality when challenged with E. ictaluri.

AbstractThe T-2 toxin is a trichothecene mycotoxin produced by certain molds of the genus Fusariumthat infect the grains, wheat by-products, and oilseed meals used in the production of animal feeds. An aquarium study was conducted with juvenile channel catfish Ictalurus punctatus. Experimental diets were prepared by replacing the untreated casein in a semipurified diet with casein treated with pure T-2 toxin in the amounts necessary to produce five levels of the toxin. Dietary concentrations were 0, 0.625, 1.25, 2.5, and 5.0 mg/kg of diet. A concurrent study with similarly sized channel catfish was conducted to substantiate the toxicity of the T-2 toxin. This study required feeding the control diet at the same levels of daily consumption (pair-feeding) as in the treatments with the three highest levels of T-2 toxin (1.25, 2.5, and 5.0 mg/kg) to compare differences in weight gain, feed conversion, hematocrit, and survivability. After 8 weeks, significant (P< 0.05) reductions in growth were observed for all treatments fed T-2 toxin compared with the control diet. Significantly poorer feed conversion was found only for the highest level of T-2 toxin. Hematocrit values were adversely affected by the inclusion of T-2 toxin at 1.25, 2.5, and 5.0 mg/kg. Pair-fed catfish had a significantly greater increase in body weight than fish fed the highest level of mycotoxin only. Pair-fed treatments had hematocrit values that were very similar to those of the control and significantly higher than those of fish receiving 1.25, 2.5, and 5.0 mg/ kg. The survivability of the fish fed T-2 toxin at 2.5 and 5.0 mg/kg was significantly lower than that of control fish and their pair-fed counterparts. Histopathological anomalies of stomach, head, and trunk kidneys were observed in fish receiving the three highest levels of T-2 toxin. These results demonstrate that this feed-borne mycotoxin is toxic to juvenile channel catfish.

AbstractWe determined the nutritional value of large zooplankton (500–1,000 μm) from fertilized and nonfertilized channel catfish Ictalurus punctatusnursery ponds. Proximate composition, amino acids, fatty acids, and assimilated algal pigments were statistically compared between pond groups. Analyses of vitamin and mineral composite samples of zooplankton from fertilized and nonfertilized ponds are presented. Treatment and control pond zooplankton were similar in nutritional value. Only two fatty acids (16:0 and 20:4[n-6]) were significantly different (P< 0.05) between fertilized and nonfertilized ponds, but total n-3 and n-6 highly unsaturated fatty acids were not different. The zooplankton in this study met or exceeded all nutritional requirements of channel catfish fry except that zooplankton in nonfertilized ponds appeared to contain less -than the required levels of pantothenic acid and vitamin B6. However, no statistical comparison of vitamins was made between fertilized and nonfertilized ponds. Because of the high nutritional value of zooplankton present in channel catfish nursery ponds, the importance of maintaining high densities of zooplankton is confirmed. If fertilization practices maintain large numbers of zooplankton, all fry nutritional requirements can be met through the natural biota. Supplemental feeding with prepared diets may still be necessary to ensure that sufficient food sources are available to the fry for optimum growth and survival.