Menghe H. Li

Comparison of the Channel Catfish, Ictalurus punctatus (NWAC103 Strain) and the Channel × Blue Catfish, I. punctatus × I.furcatus, F1 Hybrid for Growth, Feed Efficiency, Processing Yield, and Body Composition

Abstract A pond trial was conducted to compare growth, feed efficiency, survival, processing yield, and body composition of the NWAC103 strain of channel catfish, Ictalurus punctatus and the F1 channel X blue catfish hybrid (CB hybrid), I. punctatus X I. furcatus. Each genotype was stocked into five 0.4-ha earthen ponds at a rate of 14,820 fish/ha. Initial weights were 24.9 and 31.8 g/fish for the NWAC103 strain of channel catfish and the CB hybrid, respectively. Fish were fed a commercial, 28% protein diet once daily to satiation for 160 days. Compared to NWAC103 channel catfish, the CB hybrid consumed more diet, gained more weight, converted diet more efficiently, and had higher net production, survival, carcass yield, nugget yield, visceral fat, fillet moisture and protein, and a lower level of fillet fat. There were no differences in fillet yield and fillet ash concentration between the channel X blue catfish hybrid and the channel catfish. These results suggest that the CB hybrid possesses superior production traits compared with the NWAC103 channel catfish. However, problems of producing a large number of hybrid fingerlings in a cost-effective manner remain to be resolved before the hybrid catfish can be commercially farmed.

Comparison of Microbial Phytase and Dicalcium Phosphate for Growth and Bone Mineralization of Pond-Raised Channel Catfish, Ictalurus punctatus

Abstract This study evaluated the use of microbial phytase as replacement for inorganic phosphorus supplement in diets for pond-raised channel catfish, Ictalurus punctatus. Channel catfish fingerlings (average weight: 23 g) were stocked into twelve 0.04-ha ponds at a rate of 18,525 fish/ha. Four ponds were used for each treatment. Fish were fed one of three experimental diets containing 250 or 500 FTU (phytase unit) phytase/kg, or 0.75% dicalcium phosphate once daily to satiation from May to October, 2000. No differences were observed in diet consumption, weight gain, feed conversion ratio, survival, or bone ash and phosphorus concentrations among fish fed different diets. Based on these results it appears that a phytase concentration of 250 FTU/kg diet applied post-pelleting can replace the dicalcium phosphate supplement in channel catfish diets without affecting fish growth and bone mineralization under pond culture conditions. We recommend that a phytase level of 500 FTU/kg diet be used and that the diet contain a total phosphorus level of 0.6% or above to ensure that adequate amount of phosphorus is available to channel catfish. Based on current prices of phytase and inorganic phosphorus sources, it is economical to use phytase in catfish diets.

Use of Cottonseed Meal in Aquatic Animal Diets: A Review

Abstract Cottonseed meal is a plant protein source that is abundant in most parts of the world, relatively high in protein, and generally less expensive per unit of protein than soybean meal. It is highly palatable and readily digested by most aquatic animals, though generally not as digestible as soybean meal. Its use in aquaculture feeds may be limited because of the potential toxic effects of free gossypol and its relatively low available lysine and methionine content. However, depending on economics, the protein quality of cottonseed meal can be improved by supplementing it with lysine or both lysine and methionine. Also, the concentrations of free gossypol in diets containing significant levels of cottonseed meal are typically below the levels that are detrimental to many aquatic animals. However, even as a partial replacement of soybean meal, cottonseed meal has generally been used at relatively low levels in aquatic animal diets, partially because the safe levels of cottonseed meal appear to differ...

Ochratoxin A fed to channel catfish (Ictalurus punctatus) causes reduced growth and lesions of hepatopancreatic tissue

Abstract Ochratoxins are a group of secondary metabolites produced by fungal organisms belonging to Aspergillus and Penicillium genera. Ochratoxin A (OA) is the most abundant of this group of mycotoxins and is more toxic than other ochratoxins. It contaminates corn, cereal grains and oilseeds that have been infected with certain species of molds of the two previously indicated genera. Ochratoxin A can adversely affect animal performance. The effects of OA on channel catfish have not been documented. An experiment was conducted in aquaria with juvenile channel catfish to evaluate the effect of feeding graded levels of OA in a semipurified diet for 8 weeks on growth, feed conversion ratio (FCR), hematology, survival, and histopathology of liver and kidney. Channel catfish, initial body weight 6.1 g/fish, were fed diets containing 0, 0.5, 1.0, 2.0, 4.0, or 8.0 mg OA/kg diet supplied from culture material containing 80 mg OA/kg. Significant (P≤0.05) reductions in body weight gain were observed after only 2 weeks and at each successive 2-week weighing interval for catfish fed diets containing 2.0 mg OA/kg diet or above. At week 8, weight gain was significantly reduced in catfish fed diets containing 1.0 mg OA/kg or above. Feed conversion ratio was significantly poorer for catfish fed diets containing 4.0 or 8.0 mg OA/kg of diet. Hematocrit was significantly lower for catfish fed 8.0 mg OA/kg, but no significant (P>0.05) differences in white blood cell (WBC) count were observed for catfish at any dietary levels of OA. Survival was high for catfish fed diets containing 0–4 mg OA/kg, but fish fed the diet containing 8.0 mg OA/kg had significantly lower survival compared with those of the other treatments. Histopathological examination of liver and posterior kidney at 8 weeks revealed that there was increased incidence and severity of melanomacrophage centers in hepatopancreatic tissue and posterior kidney for catfish fed dietary concentrations of 2.0 mg OA/kg or above. Exocrine pancreatic cells that normally surround the hepatic portal veins of channel catfish were reduced in number or absent in livers of fish fed 1.0 mg OA/kg diet or greater.

Effects of Dietary Protein Concentration on Production Characteristics of Pond-Raised Channel Catfish Fed Once Daily or Once Every other Day to Satiation

Abstract We evaluated the effects of dietary protein and feeding regime on the production characteristics, processing yield, and body composition of channel catfish Ictalurus punctatus. Stocker-size fish with an average weight of 93 g/fish were stocked into twenty-four 0.4-ha ponds at a rate of 11,115 fish/ha. Fish were fed once daily or every other day (EOD) to apparent satiation with three commercial diets containing 28, 32, or 35% protein in a 2 × 3 factorial arrangement for 110 d. Compared with daily feeding, EOD feeding resulted in lower average net production, feed consumption, weight gain per fish, and feed conversion ratio and produced fewer marketable fish. The EOD ponds required less aeration than ponds with fish fed daily. Fish fed EOD had lower visceral fat and fillet fat, carcass yield, and fillet yield compared with fish fed daily. Dietary protein levels had no effect on net production, aeration time, processing yield, fillet composition, and feed consumption and weight gain per fish. Howeve...

Response of Channel Catfish to Diets Containing T-2 Toxin

Abstract The T-2 toxin is a trichothecene mycotoxin produced by certain molds of the genus Fusarium that 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 ...

Growth and Feed Efficiency of Juvenile Channel Catfish Reared at Different Water Temperatures and Fed Diets Containing Various Levels of Fish Meal

Abstract Channel catfish Ictalurus punctatus do not feed well at low temperatures. It is generally thought that a diet containing fish meal enhances feed palatability at low temperatures since fish meal is highly palatable to fish. There is a lack of information on the effects of fish meal levels on the growth performance of channel catfish reared at low temperatures. Therefore, a study was conducted in a recirculating system to examine the effects of fish meal levels on the feed consumption, weight gain, and feed efficiency of juvenile channel catfish reared at various temperatures. Fish with an initial weight of 9.6 ± 0.1 g were stocked in 23-L clear polycarbonate tanks maintained at approximately 17, 21, or 27 °C. The fish were fed with diets containing 0, 4, or 8% menhaden Brevoortia spp. fish meal for 9 weeks. There was a significant interaction between water temperature and fish meal level with respect to weight gain. At 27°C, fish fed diets containing 4% and 8% fish meal gained significantly more w...

Effect of Daily Feed Intake on Feed Efficiency of Juvenile Channel Catfish

Abstract Pond-raised channel catfish Ictalurus punctatus fed to satiation typically have lower feed efficiency (the ratio of weight gain to feed consumption) than fish fed a restricted ration. It is not clear whether the reduction in feed efficiency of fish fed to satiation is caused by wasted feed or by less efficient feed utilization. Two studies were conducted using 110-L flow-through aquaria to evaluate the relationship among the feed intake, growth rate, and feed efficiency of juvenile channel catfish. In experiment 1, 20 fish averaging 46 g were fed once daily at 0.5% to 3.0% of body weight (BW) or to satiation for 2 weeks. In experiment 2, 15 fish averaging 37 g were fed once daily at 1.0% to 3.0% BW or to satiation for 4 weeks. Fish in the satiation group were fed as much as they would consume within 40 min, and the remaining feed pellets were removed and counted to determine the amount of feed consumed. In both experiments, weight gain increased as feed intake increased. Feed efficiency improved ...

Effects of Variable Periods of Food Deprivation on the Development of Enteric Septicemia in Channel Catfish

Enteric 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. ictaluri in 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. ictaluri in aquarium water was negligible. These data suggest that when E. ictaluri is present in the water, feeding fish increases mortality by enhancing oral exposure to the pathogen.

Effects of dietary protein concentration and L-carnitine on growth, processing yield, and body composition of channel catfish × blue catfish F1 hybrids

Abstract A study was conducted in earthen ponds to evaluate effects of dietary protein concentration and l-carnitine supplementation on feed consumption, weight gain, feed conversion ratio (FCR), processing yield, and body composition of hybrid catfish (female channel catfish Ictalurus punctatus × male blue catfish I. furcatus). Hybrid catfish fingerlings with a mean initial weight of 66 g/fish were stocked into twenty 0.04-ha earthen ponds at a density of 17,290 fish/ha. Five ponds were randomly allotted to each dietary treatment in a complete randomized design. Fish were fed one of three practical diets containing 28, 32, or 36% crude protein without l-carnitine and a 28% protein diet containing l-carnitine at 500 mg/kg once daily to apparent satiation for a 151-d growing season. Dietary protein levels ranging from 28% to 36% did not affect feed consumption, weight gain, or FCR of catfish hybrids fed to apparent satiation. Fish fed the 36% protein diet had a higher fillet yield than fish fed the 28% pro...