Combining Ability of Channel Catfish, Ictalurus punctatus, Females and Blue Catfish, I. furcatus, Males for Early Growth, Growth Variation, Disease Resistance, and Carcass Yield of their Progeny
Type of DegreePhD Dissertation
Fisheries and Allied Aquacultures
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The hybrid between channel catfish (I. punctatus) females and blue catfish (I. furcatus) males is considered the best catfish genotype for commercial catfish farming due to their faster growth rate, better survival rate, disease resistance, better carcass yield and seinability. However, the hybrid is not a panacea, and genetically improved hybrids might be developed by improving the parent species, especially by selecting for female channel catfish and male blue catfish that have increased combining abilities. Reciprocal recurrent selection for the parent species could be conducted to improve traits of the hybrid progeny, however estimation of general combining ability (GCA) and specific combining ability (SCA) is necessary to determine the feasibility and the best approach to the reciprocal recurrent selection. Twenty channel catfish females and twelve blue catfish males were crossed in a 20 x12 factorial mating design, but an unbalanced design resulted as only 40 families had adequate hatch. The 40 hybrid families were evaluated for their early performance traits in three different rearing systems at two ages. The body weight, weight gain, coefficient of variation (CV) in body weight, survival rate from natural Aeromonas hydrophila infection, and dressout percentage were analyzed to estimate genetic component variances. The estimates for variance of combining ability showed that variance for early growth of hybrid catfish in all the three rearing systems at two ages was significantly (P<0.05) affected by the additive gene actions attributable to the channel catfish female parent. The genetic effects controlling the CV in body weight when hybrids were reared in flow-through system was additive gene actions However, when the hybrids were further reared in recirculating system, the CV became attributable to dominant gene actions. The resistance of hybrid catfish to Aeromonas hydrophila was significantly affected by the additive gene effects of the blue catfish male parent. The dressout percentage of hybrid catfish was affected by the dominant gene actions attributable to the specific cross of channel and blue catfish parents. Overall, the combining abilities indicate that reciprocal recurrent selection for early traits appears to have potential to improve the performance of F1 hybrid catfish.