Bruce B. Manning

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.

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 ...

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 ...

Genetic variation in feed consumption, growth, nutrient utilization efficiency and mitochondrial function within a farmed population of channel catfish (Ictalurus punctatus)

We evaluated the effects of diets (32/4 or 36/6 percent protein/fat) and six channel catfish families for growth performance characteristics. Two families with fast- (C) and slow- (D) growth rate and with low and high feed efficiency (FE) were selected for analyses of mitochondrial complex enzymatic activities (I, II, III, and IV) and gene expression (ND1, CYTB, COX1, COX2, ATP6) levels in liver, muscle, and intestine. There were significant differences in growth rate and nutrient retention among the families. Mitochondrial enzymatic complex activities (I-V) in the tissues were all lower in family C. Four of the five genes were down-regulated in the liver and up-regulated in the muscle for the fast growing family C. There were significant differences between diets for some mitochondrial respiratory chain enzyme activities and gene expression levels. Significant diet×family interactions were observed for some enzyme activities and gene expression levels. Changes in mitochondrial respiratory chain enzyme activities and gene expression levels provide insight into the cellular mechanisms of fish with differences in growth rate and feed efficiency. Results also suggest that genotype×diet interactions should be accounted for when considering strategies for using mitochondrial function as a criteria in channel catfish selection programs for improved growth performance characteristics.

Exposure to Feedborne Mycotoxins T-2 Toxin or Ochratoxin A Causes Increased Mortality of Channel Catfish Challenged with Edwardsiella ictaluri

Abstract To 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 ochraceus culture 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 ictaluri suspended in nutrient broth that provided an estimated 2.25 × 106 colony 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...

Effects of Maintenance Feeding Regimens on Weight Gain, Feed Efficiency, and Body Condition of Pond-Raised Channel Catfish

Abstract This study evaluated the effects of initial fish size and weekly feeding frequency during the growing season on production characteristics and body condition of pond-raised channel catfish Ictalurus punctatus. Two sizes of channel catfish (averaging 39 or 249 g/fish) were stocked into eighteen 0.04-ha ponds at a density of 14,820 fish/ha. On days fed fish were fed to apparent satiation with a commercial 28% protein diet for 15 weeks. Fish fed once weekly to satiation gained 92% or 39% of initial weight for small and large fish, respectively. Maintenance feeding frequency (satiation) for these sizes of fish stocked at 14,820 fish/ha would be less frequent than once weekly. The condition factor improved as weekly feeding frequency increased. Larger fish had a better survival than smaller fish. However, fish survival was not affected by weekly feeding frequency. Based on results from the present study, it appears that feeding once weekly to satiation can maintain the body weight of advanced fingerli...

The effect of Fusarium mycotoxins deoxynivalenol, fumonisin, and moniliformin from contaminated moldy grains on aquaculture fish.

Fusarium spp. are types of fungi that invade agriculturally important grains, such as corn and wheat, where they may produce mycotoxins that are harmful to the productivity and health of food animals, such as swine, poultry, and aquacultural fish. Because corn and wheat are used for other industrial purposes, such as ethanol and flour production, by-products of these processes are available to supplement or replace expensive grains in fish feed formulations. Consequently, grain by-products have come under scrutiny as possible sources of feed-borne Fusarium mycotoxins. Evaluation of the effects of Fusarium mycotoxins on productivity of fish used in aquaculture has been the subject of recent research.