Ž .
Aquaculture 187 2000 153–161 www.elsevier.nlrlocateraqua-online
Effects of dietary carnitine on growth rates and ž
body composition of hybrid striped bass Morone saxatilis male x M. chrysops female
Ronald G. Twibell, Paul B. Brown
Department of Forestry and Natural Resources, Purdue UniÕersity, West Lafayette, IN 47907-1159 USA Accepted 29 November 1999
Abstract
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 mgrkg diet. Dietary treatments were fed to apparent satiation
twice daily to triplicate groups of hybrid striped bass initially weighing 13.5 grfish. At the end of the 8-week feeding trial, feed intake and weight gain of fish fed 369.7 mg carnitinerkg diet were
significantly increased compared to fish fed the basal diet containing 2.1 mg carnitinerkg diet. However, there were no significant differences in feed intake or weight gain among fish fed 2.1,
41.0 or 212.0 mg carnitinerkg diet. Feed efficiency, total liver lipid concentration, intraperitoneal
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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. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Carnitine; Fish nutrition; Hybrid striped bass; Lipid
1. Introduction
The ability of dietary carnitine to increase growth rates and reduce tissue lipid concentrations has been evaluated in several species of fish, with mixed results.
Corresponding author. Tel.: q1-765-494-4968; fax: q1-765-496-2422. Ž
. E-mail address: pbfnr.purdue.edu P.B. Brown .
0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž
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Carnitine, synthesized in vivo from lysine and methionine, is required for transport of long-chain fatty acids into the mitochondria, which is the site of beta oxidation. Early
research with fish indicated that carnitine increased fatty acid oxidation in tissues of Ž
. Ž
. rainbow trout Bilinski and Jonas, 1970 . More recently, Ji et al.
1996 reported increased fatty acid oxidation in liver of Atlantic salmon fed 3700 mg carnitinerkg diet,
which was accompanied by reduced lipid levels in muscle and viscera. Feeding trials with other species of fish have also demonstrated the lipotropic effects of dietary
Ž carnitine Santulli and D’Amelio, 1986a; Santulli et al., 1988; Burtle and Liu, 1994;
. Jayaprakas et al., 1996 . However, carnitine had no significant effect on tissue lipid
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concentrations in rainbow trout fed 230 mg carnitinerkg diet Rodehutscord, 1995 or Ž
. hybrid tilapia fed 150 or 300 mg carnitinerkg diet
Becker et al., 1999 . Lipid concentrations in muscle and liver of red sea bream increased as dietary carnitine
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concentration increased from 75 to 2088 mgrkg diet Chatzifotis et al., 1995 . Dietary carnitine has also been shown to increase growth rates of some species of fish
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Santulli and D’Amelio, 1986a; Torreele et al., 1993; Keshavanath and Renuka, 1998 , Ž
although a positive response has not been observed in all species Rodehutscord, 1995; .
Ji et al., 1996 . Saltwater fish are apparently able to acquire carnitine from the environment, as well as the diet, as growth rates of European sea bass were significantly
Ž increased when carnitine was dissolved in the water of the rearing tanks Santulli and
. D’Amelio, 1986b . The growth promoting effects of dietary carnitine have generally
been explained by increased utilization of dietary energy resulting from increased Ž
. oxidation of fatty acids Becker et al., 1999 . However, increased fatty acid oxidation
was observed in Atlantic salmon fed 3700 mg carnitinerkg diet without a significant Ž
. Ž
. improvement in weight gain or feed efficiency Ji et al., 1996 . Chatzifotis et al. 1996
reported significant improvements in feed consumption and growth rates, but no change in feed conversion, when red sea bream were fed 2088 mg carnitinerkg diet. Thus, it is
Ž . apparent that the mechanism s of growth enhancement of dietary carnitine is not clearly
understood. The objective of this experiment was to evaluate the effects of dietary carnitine on
growth and body composition of hybrid striped bass.
2. Materials and methods
