Patricia L. Duncan

Enhanced Bacterial Disease Resistance of Transgenic Channel Catfish Ictalurus punctatus Possessing Cecropin Genes

The cecropin B gene from the moth Hyalophora cecropia, driven by the cytomegalovirus promoter, was transferred to the channel catfish Ictalurus punctatus. Transgenic individuals (P1) were mated to produce individuals (F1) that exhibited enhanced disease resistance and survival when challenged with pathogenic bacteria. During the epizootic of Flavobacterium columnare in an earthen pond, the percentage of transgenic individuals containing preprocecropin B construct that survived (100%) was significantly greater (P <0.005) THAN THAT OF NONTRANSGENIC CONTROLS (27.3%). ALSO, WHEN CHALLENGED IN TANKS WITH EDWARDSIELLA ICTALURI, THE CAUSATIVE AGENT OF ENTERIC SEPTICEMIA OF CATFISH, THE PERCENTAGE OF TRANSGENIC INDIVIDUALS CONTAINING CATFISH IG LEADER CECROPIN B CONSTRUCT THAT SURVIVED (40.7%) WAS SIGNIFICANTLY GREATER (P <0.01) THAN THAT OF NONTRANSGENIC CONTROLS (14.8%). THERE WERE NO PLEIOTROPIC EFFECTS OF THE TRANSGENES, AND GROWTH RATES OF THE TRANSGENIC AND NONTRANSGENIC SIBLINGS WERE NOT DIFFERENT (P > 0.05). Inheritance of the transgene by the F1 generation, 20.2% to 30.7% was typical of that in studies with transgenic channel catfish.

Influence of vitamin C on the folate requirement of channel catfish, Ictalurus punctatus, for growth, hematopoiesis, and resistance to Edwardsiella ictaluri infection

Abstract Channel catfish were fed a semipurified basal diet containing 0, 0.4, or 4.0 mg folic acid/kg with 0, 20, or 200 mg vitamin C/kg in a factorial design in aquaria (29±2°C) for 25 weeks, and growth, survival, and hematological measurements were determined. The remaining fish were overwintered (25 weeks) in circular raceways at ambient outdoor temperature, fed the same experimental diets and challenged with Edwardsiella ictaluri when the water had reached 26°C. Dietary supplementation of folic acid had no effect on any measurement except hematocrit without dietary vitamin C. When the marginal level of vitamin C (20 mg/kg) was fed, hematological measurements increased maximally with the low or high supplement of folic acid (0.4 or 4.0 mg/kg), but weight gain and RBC mean corpuscular volume (MCV) did not respond to folic acid supplementation. When the high level of vitamin C (200 mg/kg) was fed, weight gain improved and MCV decreased maximally with the highest supplement of folic acid. Fish challenged with E. ictaluri showed maximum survival and antibody production when 0.4 or 4.0 mg folic acid/kg was fed with the high level of vitamin C, but only the highest supplement of folic acid improved survival when the diet contained the marginal level of vitamin C. Simultaneous supplementation of both vitamins at the highest levels resulted in the lowest incidence of morphologically abnormal blood cells. These results indicate that the dietary concentration of vitamin C influences the response of channel catfish to different dietary levels of folic acid.