Effects of dietary astaxanthin on the growth and skin and muscle pigmentation of sexually immature rainbow trout Oncorhynchus mykiss (Walbaum, 1792) (Teleostei: Salmonidae)

This study was conducted to investigate the effects of dietary synthetic astaxanthin on the growth performance and skin and muscle pigmentation of sexually immature rainbow trout. Four astaxanthin supplemented diets were prepared to contain 50, 100, 150 and 200mg astaxanthin kg^-1 diet. The basal diet without astaxanthin supplementation was used as a control. Juvenile rainbow trout of the similar size (20.07±1.45g) were fed with these experimental diets for 30 days. Results showed that there were no significant differences in weight gain, specific growth rate, condition factor, survival rate and feed conversion ratio among all treatments (P 0.05). The skin carotenoid content was significantly affected by the dietary supplementation (P 0.05) and the lowest carotenoid content was measured in the treatments of the control and the fish fed 50 mg astaxanthin kg-1 diet (P 0.05). However, the fish fed 200mg astaxanthin kg^-1 diet demonstrated the highest carotenoid content in the skin (P 0.05). Although the muscle carotenoid content increased in all groups, this augmentation was significantly prominent in the fish received the higher concentration of astaxanthin through the feed. According to the obtained results, it is proposed that in sexually immature rainbow trout, astaxanthin is mainly deposited in muscle in compared to skin. Also, diet supplementation with astaxanthin is necessary for skin pigmentation in rainbow trout.