Effects of dietary conjugated linoleic acids and total dietary lipid concentrations on growth responses of juvenile channel catfish, Ictalurus punctatus

Abstract

Abstract Dietary conjugated linoleic acids (CLA) have been shown to alter growth rates and tissue lipid concentrations in some species of fish, but have not been evaluated in channel catfish. In the current study, a 3×3 factorial design was used to examine the effects of dietary CLA and total dietary lipid concentrations on growth rate, tissue proximate composition and nutrient retention of channel catfish. Nine dietary treatments were formulated to contain either 0%, 0.5% or 1.0% CLA in diets containing 5.0%, 7.5% or 10.0% total lipid. Each diet was fed to apparent satiation twice daily to triplicate groups of fish initially weighing 13.4 g/fish. At the end of the 8-week feeding trial, weight gain, feed efficiency, feed intake and tissue proximate composition were not significantly affected by dietary CLA. However, protein retention was significantly affected by a dietary CLA×lipid interaction and values tended to reflect carcass crude protein concentrations. The effects of varying total dietary lipid concentrations on growth response and tissue composition were more pronounced. Feed efficiency, carcass lipid concentration, protein retention and energy retention were significantly increased in fish fed 7.5% and 10.0% dietary lipid compared with fish fed 5.0% dietary lipid. Hepatosomatic index (HSI) was significantly reduced and liver total lipid concentrations were significantly increased in fish fed diets containing 10.0% lipid compared with fish fed diets containing 5.0% lipid. Liver total lipid and HSI values of fish fed 7.5% dietary lipid were intermediate to those of fish fed 5.0% and 10.0% lipid. Results of this study indicate that dietary CLA have little potential for improving growth responses of channel catfish. Variable responses to dietary CLA among species may be the result of variation in energy metabolism or differences in composition of CLA supplements evaluated.