Replacing Soybean Meal with Alternative Protein Sources in Diets for Pond‐raised Hybrid Catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus

The present study investigated the replacement of soybean meal with combinations of two or three alternative protein sources in diets for pond‐raised hybrid catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus. Alternative protein sources evaluated included cottonseed meal, distillers dried grains with solubles (DDGS), peanut meal, and porcine meat and bone meal (PMBM). Hybrid catfish fingerlings with a mean initial weight of 35 g/fish were stocked into 25 earthen ponds (0.04 ha) at a density of 14,826 fish/ha. Fish were fed once daily to apparent satiation for 166 d. No significant differences were observed for total diet fed, net yield, weight gain, survival, carcass yield, fillet yield, or fillet proximate composition among dietary treatments. Results show soybean meal may be completely replaced by combinations of cottonseed meal and one or two other alternative protein sources including DDGS, peanut meal, and PMBM in the diet without markedly affecting production and processing characteristics and fillet proximate composition of pond‐raised hybrid catfish. These alternative diets may be used during foodfish production when prices are favorable.     

Evaluation of Low‐protein Alternative Diets for Pond‐raised Hybrid Catfish,Ictalurus punctatus × Ictalurus furcatus

A study was conducted to evaluate low‐protein traditional or alternative diets for pond‐raised hybrid catfish, Ictalurus punctatus × Ictalurus furcatus. Three 24% protein diets containing decreasing levels of soybean meal (30, 20, and 15%) and increasing levels of cottonseed meal and corn germ meal were compared with a 28% protein control diet. Hybrid catfish fingerlings (mean initial weight = 71 g/fish) were stocked into 20 earthen ponds (0.04 ha) at a density of 14,826 fish/ha with five ponds per dietary treatment. Fish were fed once daily to apparent satiation for a 191‐d growing season. There were no significant differences in total diet fed, net yield, weight gain, feed conversion ratio (FCR), survival, or fillet proximate nutrient composition among dietary treatments (P ≥ 0.10). However, regression analysis showed for fish fed 24% protein diets there was a linear increase in FCR as soybean meal levels decreased (P = 0.06). Compared with fish fed the 28% protein control diet, fish fed 24% protein diets had lower carcass and fillet yield. Results demonstrate a 24% protein alternative diet containing 20% soybean meal may be substituted for 28% protein diets for hybrid catfish during food fish production.     

Efficacy of Crystalline Lysine in Alternative Diets for Pond‐raised Hybrid Catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus

A study was conducted to examine the efficacy of crystalline lysine in alternative diets for pond‐raised hybrid catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus. Two 28% protein alternative diets supplemented with l ‐lysine HCl at the required level based on 62% (previously published value) or 100% lysine availability were compared with a traditional 28% protein control diet. Hybrid catfish fingerlings (mean initial weight = 43 g/fish) were stocked into 15 earthen ponds (0.04 ha) at a density of 14,826 fish/ha with five ponds per treatment. Fish were fed once daily to apparent satiation for a 173‐d growing season. There were no significant differences in total diet fed, net yield, weight gain, and survival among dietary treatments. There were also no significant differences in carcass yield, fillet yield, and fillet proximate composition and fillet lysine concentration among treatments. Fish fed the traditional control diet had slightly, but significantly, lower feed conversion ratio than fish fed alternative diets, which is likely related to higher dietary fiber levels in the alternative diets. Results from this study show that crystalline lysine can be considered 100% available when used to supplement lysine‐deficient diets for pond‐raised hybrid catfish.     

Evaluation of porcine ileum models of enterocyte infection by Lawsonia intracellularis

The early interaction of Lawsonia intracellularis with host cells was examined with the use of porcine ileum models. Two conventional swine were anesthetized, and ligated ileum loops were prepared during abdominal surgery. The loops were inoculated with 108 L. intracellularis or saline. After 60 min, samples of each loop were processed for routine histologic and electron microscopic study. Histologic and ultrathin sections of all the loops appeared normal, with no apposition of bacteria and host cells or bacterial entry events in any loop. Portions of ileum from a single gnotobiotic piglet were introduced as xenografts into the subcutis of each flank of 5 weaned mice with severe combined immunodeficiency disease. After 4 wk, 108 L. intracellularis were inoculated into each of 4 viable xenografts with a sterile needle; the other 3 viable xenografts received saline. Histologic and ultrathin sections of all the xenografts 3 wk after inoculation showed relatively normal porcine intestinal architecture, with normal crypts, crypt cell differentiation, and low villous structures; the xenografts treated with the bacteria also showed intracytoplasmic L. intracellularis within crypt and villous epithelial cells. Thus, entry of L. intracellularis into target epithelial cells and multiplication may not be sufficient alone to directly cause cell proliferation. A proliferative response may require active division of crypt cells and differentiation in conjunction with L. intracellularis growth.     

Evaluation of age-related effects on the antiviral activity of interferon and induction of 2-5A synthetase in testicular cell cultures derived from swine of various ages

The antiviral activity of recombinant DNA-derived bovine alpha 1(-1) interferon on an established swine testicular cell line and primary testicular cell cultures derived from swine of various ages (2 days, 3 weeks, and 5 weeks) was determined. Bovine interferon induced a dose-dependent increase in 2-5A synthetase in testicular cells, regardless of the source of the cells. Furthermore, interferon inhibited replication of vesicular stomatitis virus to an equivalent extent in all testicular cell cultures. The results indicate that 2-5A synthetase is a reliable marker of interferon activity in swine testicular cell cultures and that the induction of 2-5A synthetase and antiviral effects of recombinant bovine interferon in primary testicular cell cultures are not dependent on the age of the donor animal.     

Multi-Locus DNA Fingerprinting of Channel Catfish Ictalurus punctatus

Abstract.— Similarities among multi-locus DNA fingerprints of five channel catfish Ictalurus punctatus strains and the ability to identify the strain of a fish based on its fingerprint pattern were investigated. Five restriction enzymes and 13 multi-locus DNA probes were screened to identify enzyme-probe combination useful for DNA fingerprinting channel catfish. Restriction enzymes Hinf I and Dpn II, in combination with probes (CAC)n, (CGC)n, (CTC)n, (ATCC)n, and (GATA)n, produced useful fingerprints (20–30 resolvable bands for each enzyme-probe combination). Thirty individuals (3 pools of 10 individuals each) from each of five channel catfish strains (albino, Mississippi normal, USDA-102, USDA-102 select, and USDA-103) were fingerprinted with all useful enzyme-probe combinations. Band sharing among samples was higher within strains than among strains and band sharing among strains was higher for strains whose breeding history indicated a high degree of relatedness. Individual fingerprints of 18 fish from each of the USDA-102 select and USDA-103 strains revealed no strain-specific bands, but several diagnostic bands (present at high frequencies in either USDA-102 select or USDA-103 strains and at a low frequencies in other strains) were identified. Band sharing at diagnostic bands was used to correctly identify fish as USDA-102 select or USDA-103 strains with 82% accuracy from fingerprints of 17 USDA-102 select strain fish, 18 USDA-103 strain fish, and 38 fish collected from three commercial farms.     

Synthesis of macroporous minerals with highly ordered three-dimensional arrays of spheroidal voids

Titania, zirconia, and alumina samples with periodic three-dimensional arrays of macropores were synthesized from the corresponding metal alkoxides, using latex spheres as templates. In a fast, single-step reaction, the monomeric alkoxide precursors permeate the array of bulk polystyrene spheres and condense in air at room temperature. Close packed, open-pore structures with 320- to 360-nanometer voids are obtained after calcination of the organic component at 575 degreesC. The examples presented demonstrate the compositional diversity possible with this technique. The resulting highly structured ceramics could have applications in areas ranging from quantum electronics to photocatalysis to battery materials.     

Effects of varying dietary compositions using common feed ingredients on growth and feed efficiency of pond‐raised channel catfish Ictalurus punctatus (Rafinesque)

Two experiments were conducted to evaluate various ingredient combinations in a 28% or 32% protein diet for optimum performance of channel catfish Ictalurus punctatus. All diets contained soybean meal and corn, but with or without cottonseed meal, wheat middlings or fish meal (FM). Channel catfish fingerlings were stocked into 0.04 ha earthen ponds at 18 530 fish ha^?1. Fish were fed one of eight diets once daily to apparent satiation for two growing seasons. Results demonstrated that the dietary ingredient composition used had significant effects on fish performance, but magnitude of differences was relatively small. Overall, diets containing FM resulted in greater weight gain (Experiments 1 and 2) and lower feed conversion ratio (Experiment 1) than fish fed all‐plant diets. However, certain combinations of plant ingredients provided the similar fish growth as some diets containing FM. There were no significant differences in weight gain between fish fed soybean meal–corn or soybean meal–corn–wheat middlings‐based diets with cottonseed meal or FM. The use of wheat middlings in the diet had no significant effects on fish production characteristics.     

Comparative Susceptibility of Channel Catfish,Ictalurus punctatus; Blue Catfish,Ictalurus furcatus; and Channel (♀) × Blue (♂) Hybrid Catfish to Edwardsiella piscicida,Edwardsiella tarda,and Edwardsiella anguillarum

Members of the genus Edwardsiella are important pathogens of cultured and wild fish globally. Recent investigations into the phenotypic and genotypic variation of Edwardsiella tarda have led to the segregation of E. tarda into three distinct taxa: E. tarda, Edwardsiella piscicida, and Edwardsiella anguillarum. In catfish aquaculture in the southeastern USA, E. piscicida has been more commonly associated with disease than E. tarda or E. anguillarum, and recent research has demonstrated E. piscicida to be more pathogenic in channel catfish than E. tarda or E. anguillarum. Anecdotal reports from industry suggest an increased prevalence of E. piscicida associated with the culture of channel (♀) × blue (♂) hybrid catfish. This work investigated the comparative susceptibility of channel catfish, blue catfish, and their hybrid cross to molecularly confirmed isolates of E. tarda, E. piscicida, and E. anguillarum. There was significantly higher mortality in hybrid catfish compared to channel catfish following intracoelomic injection of E. piscicida. To our knowledge, E. piscicida is the first bacterial pathogen to demonstrate increased pathogenicity in hybrid catfish compared to channel catfish.