Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2006
Publication Date: 6/21/2007
Citation: Li, M.H., Robinson, E.H., Bosworth, B.G. 2007. Effects of Dietary Protein Concentration and L-carnitine on Growth, Processing Yield, and Body Composition of Channel X Blue Catfish Hybrids. North American Journal of Aquaculture 69:229-234. Interpretive Summary: Diet and genetics affect important production traits in meat animal species including farm-raised catfish. Compared to channel catfish, hybrids between blue and channel catfish have good performance for important production traits, but they tend to accumulate more fat. Increased fat accumulation can have a negative impact on fish growth and processing yield. Diet affects growth, body composition, and processing yield in channel catfish, but less is known about the effects of diet on these traits in hybrid catfish. This study was conducted to determine the effects of three dietary protein levels (28, 32, and 36%) on production, processing, and body composition traits of hybrids. In additon effects of supplementation of 28% protein diet with carnitine (a compound shown to reduce fat accumulation in other fish species) were evaluated. Although there were no differences in growth and feed conversion efficiency among treatments, fish fed the highest protein (36%) had the lowest fillet fat and the highest fillet yield. There was a trend toward reduced fillet fat in fish fed carnitine supplemented diet. Body fattiness of channel × blue catfish hybrids may be reduced by feeding high-protein diets or possibly by dietary L-carnitine supplementation. However, diet costs generally increase as protein level increases or with carnitine supplementation, therefore to be beneficial the value gained from feeding higher protein needs to be greater than the associated cost.
Technical Abstract: A study was conducted in earthen ponds to evaluate effects of dietary protein concentration and L-carnitine supplementation on production and processing traits of channel catfish × blue catfish hybrids. Hybrid fingerlings, mean initial weight = 66 g, were stocked into 20, 0.04-ha earthen ponds at a density of 17,290 fish/ha. Five ponds were randomly allotted to each treatment. Fish were fed once daily to apparent satiation for a 151-d growing season with one of three practical diets containing 28, 32, or 36% crude protein without L-carnitine and a 28%-protein diet containing 500 mg/kg L-carnitine. Dietary protein levels did not affect feed consumption, weight gain, or feed conversion ratio of 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 fed either 28%- or 36%-protein diet. The fillet fat concentration was lower in fish fed the 36%-protein diet than those fed lower-protein diets. Supplementation of 500 mg/kg L-carnitine in the diet did not affect feed consumption, weight gain, FCR, or processing yield, but there was a trend toward reduced fillet fat level by dietary L-carnitine supplementation. Results from the present study indicate that body fattiness of channel × blue catfish hybrids may be reduced by feeding high-protein diets or possibly by dietary L-carnitine supplementation.