Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/1997
Publication Date: N/A
Interpretive Summary: Commercial culture of F1 hybrids among channel and blue catfish has been suggested for improving important production traits of farmed catfish. The objectives of this study were to compare growth, feed conversion, fillet proximate composition, and resistance to the bacterium Edwardsiella ictaluri of juvenile channel catfish, blue catfish, and their reciprocal F1 hybrids fed 25% and 45% protein diets. Channel catfish were superior to other genotypes for growth and FCR regardless of diet, but the relative differences among channel catfish and other genotypes was greater for the 45% diet than for the 25% diet. The genotype x diet interaction for growth and feed conversion appeared to be due to poor palatability of the 45% diet to blue and hybrid catfish. There were no differences among genotypes for fillet proximate composition, or for mortality or antibody level after exposure to E. ictaluri. Estimation of genetic effects indicated that channel catfish additive genetic effects were favorable and heterosis was unfavorable for growth and feed conversion. The results of this study indicate that, for the strains of fish used and traits measured, channel catfish are superior to blue catfish, and F1 hybrids.
Technical Abstract: Juvenile channel catfish, blue catfish and their reciprocal F1 hybrids were fed practical-type diets containing 25 and 45% protein during a 10 week trial to determine the effects of genotype, dietary protein level, and genotype x dietary protein level interaction on growth, feed conversion ratio (FCR), fillet proximate composition, and resistance to Edwardsiella ictaluri. Rankings of genotypes for absolute weight gain, percent weight gain, and FCR (best to worst) were channel > channel female x blue male = blue > blue female x channel male for the 25% protein diet; and channel > channel x blue > blue x channel = blue for the 45% diet. Diet did not affect growth or FCR of channel catfish, but growth was faster and FCR better for blues and both hybrids fed the 25% than those fed the 45% diet. Channel catfish additive genetic and maternal effects were favorable, and heterosis was negative for growth and FCR. After adjusting for effects of fish size, genotype had no effect on fillet composition. Fillet protein was higher for all genotypes, and fillet lipid was lower for blues and hybrids fed the 45% diet than for fish fed the 25% diet. Genotype x dietary protein level interaction observed for growth, FCR, and fillet lipid appeared to be due to poor palatability of the 45% diet to blues and both hybrids. Survival (76-93%) and antibody levels (0.10-0.24 OD) after exposure to E. ictaluri were not affected by genotype or diet. Hybridization or introgressive breeding of blue and channel catfish would not improve the traits measured relative to purebred channel catfish for the fish strains and diets studied.