An experiment was conducted to determine the effects of supplemental dietary L-carnitine, chromium picolinate (Cr-Pic) and their combination on growth performance and serum total protein, cholesterol, triglyceride and glucose of rainbow trout (Oncorhynchus mykiss). A total of 276 rainbow trout were randomly allocated to four groups. Fish (average initial body weight = 151 ± 1.69 g) were fed a basal diet without supplemental L-carnitine and chromium picolinate in the control group. The basal diet was supplemented with either 500 mg/kg L-carnitine, 1.6 mg/kg chromium picolinate or 500 mg/kg L-carnitine plus 1.6 mg/kg chromium picolinate for experimental groups 1 (C), 2 (Cr-Pic) and 3 (C ? Cr-Pic), respectively. Fish were fed twice a day to apparent satiation for 58 days. Weight gain, growth rate, feed consumption and feed conversion ratio (feed/ gain) were calculated for the whole period. At the end of the study, six fish were chosen randomly from each tank to represent the experiment and frozen at -20°C for subsequent dorsal muscle analysis. The results showed no significant differences in final body weight, weight gain or feed conversion ratio among groups. There were also no significant differences in serum total protein, cholesterol, triglyceride or glucose concentrations among groups. Significantly higher lipid concentration of dorsal muscle was observed in experimental groups 1 and 3. In conclusion, supplemental dietary L-carnitine, chromium picolinate and their combination have no beneficial effects on improving growth performance and feed conversion ratio in rainbow trout. However, dietary L-carnitine slightly increased lipid concentration in dorsal muscle of rainbow trout.

The aim of this study was to investigate the effect of different carotenoid sources on goldfish (Carassius auratus) skin pigmentation. The value of goldfish depends on the intensity of the skin color. In the red variety of goldfish, an orange-red hue is desirable. Juvenile goldfish were fed one of five diets for five months to determine the effects of carotenoids on skin pigmentation, growth, feed efficiency, and survival: (1) astaxanthin (carophyll pink at 75 mg/kg), (2) canthaxanthin (carophyll red at 75 mg/kg), (3) Gammarus spp. (75 mg/kg), (4) Oleoresin paprika (180 mg/kg), and (5) an unsupplemented control. Growth and feed efficiency did not significantly differ among groups. Initial and final samples of head skin were measured by colorimetric analysis for lightness (L*), redness (a*), yellowness (b*), hue (Hº ab), and chroma (C ab *). The best red color (a* and Hº ab) was obtained with the astaxanthin, canthaxanthin, and paprika diets.

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