Red yeast (Phaffia rhodozyma) and its effect on growth, antioxidant activity and color pigmentation of rainbow trout (Oncorhynchus mykiss)

Efficacy of orally used of red yeast (Phaffia rhodozyma) (1.6 mg astaxanthin/g product) at 15.5 g (P1), 37.3 g (P2) and 47 (P3) g per kg diet were studied on performance, carcass composition, antioxidant activity and fillet pigmentation in rainbow trout (Oncorhynchus mykiss) weighing 208-212 g for eight weeks at 11 C. Synthetic astaxanthin (AX) (0.5 g/kg diet) and basal diet were used as controls. With an increase in P. rhodozyma concentration in diet, weight gain and specific growth rate exhibited an increase compared to basal diet (P < 0.05%). A significant difference was seen among the treatments but only P3 diet significantly demonstrated a better growth than AX diet (P < 0.05). Activity of antioxidant enzymes; superoxidase dismutase, glutathione peroxidase, total antioxidant activity, glutathione reductase, and catalase exhibited an enhancement in serum or liver samples of fish fed P. rhodozyma compared to basal diet (P < 0.05). Protein content in fillet of fish fed P3 diet was higher than both basal and AX diets (P < 0.05), but no significant difference was seen in contents of lipid, moisture, ash and pH values either among the treatments or between treatments and basal diet (P > 0.05). Water holding capacity and lipid loss in fillets of treatments were lower than fish fed basal diet (P < 0.05). By increasing P. rhodozyma concentration in fish diets, redness value exhibited a progressive increase, and the highest value was seen in P3 diet compared to other treatments (P < 0.05). These data show application of P. rhodozyma at 47 g/kg diet in trout could provide a better performance, antioxidant activities, and fillet pigmentation.