Effect of Varying the Concentration of Dietary Astaxanthin on Rainbow Trout,Oncorhynchus mykissMuscle Pigmentation

The effect of daily distribution of various dietary astaxanthin concentrations (0, 10, 15, 25, and 30 mg astaxanthin/kg diet) on rainbow trout muscle pigmentation was studied during 9 weeks. Four combined daily distribution treatments (morning/evening) of dietary astaxanthin (25/25, 25/10, 15/15, and 30/0) were tested on triplicate groups of 80 immature rainbow trout (body weight±SD, 199.6±3.7 g). Trout muscle pigmentation was evaluated on the basis of muscle astaxanthin retention and muscle color. Fish muscle astaxanthin increased with increasing dietary carotenoid concentration. There was no significant (P > 0.05) difference for muscle astaxanthin retention coefficients and muscle color parameters of fish receiving treatments 25/25 and 25/ 10 while there was a significant (P < 0.05) difference for muscle astaxanthin retention coefficients and muscle color parameters of fish receiving treatments 25/25 and 15/15 or 30/0. Astaxanthin retention coefficients were higher for lower dietary doses (15/15 or 30/0) while muscle color parameters were lower for fish receiving treatments 15/15 or 30/0. These results suggest that the level of dietary astaxanthin currently used for trout pigmentation (25/25) may be reduced by 30% by varying its daily distribution in feeds (25/10).