Effects of feeding the repartitioning agent L644,969 on growth and body composition of blue catfish, Ictalurus furcatus, fed diets containing two protein levels reared in cages

Juvenile blue catfish with an average initial weight of 110 g, were stocked into 3.5-m 3 floating cages at a rate of 200 fish/cage and fed one of four diets. Diets contained either 27 or 36% protein and either 0 or 3 mg/kg of the beta-adrenergic agonist (BAA) L644,969. There were three replicates per diet. Fish were fed all they would consume in 40 min for 94 days. There was no significant effect of protein, L644,969, or their interaction ( P > 0.05) on final individual weight, percentage weight gain, survival, and specific growth rate (SGR). No difference ( P > 0.05) in whole body composition was found between protein levels; however, fish fed diets containing L644,969 had a higher ( P < 0.05) fillet dressout and a lower ( P < 0.05) percentage of abdominal fat than fish fed control diets. The fish fed 3 mg L644,969/kg diet had 15% more protein and 28% less lipid in the fillet than fish fed control diets ( P < 0.05). Fish fed diets containing L644,969 also had a significantly higher ( P < 0.05) percentage of protein and a lower percentage of lipid in viscera than fish fed diets without the BAA. These results indicate that blue catfish reared to 485 g in cages can be fed as much as they will consume of a diet containing 27% protein without adversely affecting growth, and that the addition of 3 mg L644,969/kg to diet containing either 27 or 36% protein reduces lipid deposition in muscle and visceral depots while increasing protein accretion in muscle.