Effects of Dietary Protein Concentration and l-Carnitine on Growth, Processing Yield, and Body Composition of Channel Catfish × Blue Catfish F₁ Hybrids

Abstract

A study was conducted in earthen ponds to evaluate effects of dietary protein concentration and l-carnitine supplementation on feed consumption, weight gain, feed conversion ratio (FCR), processing yield, and body composition of hybrid catfish (female channel catfish Ictalurus punctatus × male blue catfish I. furcatus). Hybrid catfish fingerlings with a mean initial weight of 66 g/fish were stocked into twenty 0.04-ha earthen ponds at a density of 17,290 fish/ha. Five ponds were randomly allotted to each dietary treatment in a complete randomized design. Fish were fed one of three practical diets containing 28, 32, or 36% crude protein without l-carnitine and a 28% protein diet containing l-carnitine at 500 mg/kg once daily to apparent satiation for a 151-d growing season. Dietary protein levels ranging from 28% to 36% did not affect feed consumption, weight gain, or FCR of catfish hybrids fed to apparent satiation. Fish fed the 36% protein diet had a higher fillet yield than fish fed the 28% protein diet, whereas fish fed the 32% protein diet had intermediate fillet yield and fillet fat, which were not different from those of fish fed the 28% and 36% protein diets. The fillet fat concentration was lower in fish fed the 36% protein diet than in those fed lower-protein diets. Supplementation of l-carnitine at 500 mg/kg in the diet did not affect feed consumption, weight gain, FCR, or processing yield, but there was a trend toward a reduction in fillet fat level. Results from this study indicate that body fatness of channel catfish × blue catfish hybrids was reduced by feeding them a high-protein (36%) diet and that l-carnitine had a mild effect on fat reduction in hybrid catfish fed a 28% protein diet.