Effects of dietary carnitine on growth rates and body composition of hybrid striped bass (Morone saxatilis male x M-chrysops female)

The effects of carnitine were evaluated in diets fed to hybrid striped bass. The basal diet contained 34.6% crude protein supplied by casein, gelatin and crystalline L-amino acids and 6.0% lipid supplied by menhaden oil. Four dietary treatments contained L-carnitine concentrations of either 2.1, 41.0, 212.0 or 369.7 mg/kg diet. Dietary treatments were fed to apparent satiation twice daily to triplicate groups of hybrid striped bass initially weighing 13.5 g/fish. At the end of the 8-week feeding trial, feed intake and weight gain of fish fed 369.7 mg carnitine/kg diet were significantly increased compared to fish fed the basal diet containing 2.1 mg carnitine/kg diet. However, there were no significant differences in feed intake or weight gain among fish fed 2.1, 41.0 or 212.0 mg carnitine/kg diet. Feed efficiency, total liver lipid concentration, intraperitoneal fat ratio (IPF) and proximate composition of muscle and carcass were not significantly affected by dietary carnitine concentration. Serum concentrations of total and free carnitine and carnitine esters were not significantly different among fish fed any of the diets, although values tended to increase with increasing dietary carnitine. Results of this study indicate that growth rate, but not body composition, of hybrid striped bass can be improved with relatively low concentrations of dietary carnitine. (C) 2000 Elsevier Science B.V. All rights reserved.