The degree of flesh pigmentation is one of the most important quality criteria dictating the fish market value. It is well known that fish, like other animals, cannot synthesize their own coloring pigments de novo, and must obtain these pigments from their diet. In this study, four levels of black mulberry (Morus nigra) juice powder (BMP) as a natural pigment source were incorporated into a basal diet at concentrations of 0, 0.25, 0.5, and 0.75% and fed to rainbow trout weighing 100±5 g for 8 weeks in triplicate. At the end of the feeding trial, the effect of BMP on growth performance, blood biochemical parameters and fillet color was examined. Fish fed BMP showed significant enhancements in weight gain (WG), specific growth (SGR), food conversion ratio (FCR), and survival rates (SR) (P<0.05). SGR, WG and SR values were increased significantly following dietary supplementation with BMP in a dose dependent manner with the highest values in fish fed 0.75%, while the FCR was decreased (P<0.05). Body crude protein, lipid, and moisture contents were increased significantly in fish fed BMP (P<0.05). Dietary BMP has significantly decreased the levels of blood ALT, AST, and glucose (P>0.05). While the blood carotenoid concentration was increased in fish fed 0.5% BMP compared to other treated groups. Fish fed BMP showed increased fillet yellowness (b*) and redness (a*), while the fillet lightness (L*) was decreased when compared to the control (P<0.05). In conclusion, diets supplemented with BMP increased the growth performance, muscle pigmentation, and health status of rainbow trout.

The present study aimed at evaluating the influences of pomegranate peel meal on the growth performance, hematology, and blood biochemistry of rainbow trout. Fish fed at 5 varying levels of pomegranate peel meal (0 %, 1%, 2 %, 3%, and 4%) for 60 days. The obtained results showed that WG was significantly higher in fish fed at the rate of 1% than the other groups, while SGR was significantly increased in fish fed 1% and followed by the ration of 2% (P <0.05). SGR of fish fed at the rate of 4% revealed the lowest value among the groups (P <0.05). However, FCR displayed the lowest values in fish fed at the rate of 1% or 2%, while the highest value was observed in fish fed at the rate of 4% (P <0.05). The survival rate was increased by the rate of 1% than the control without differences with the other groups (P <0.05). RBCs were significantly higher in fish fed at the rate of 0%, 1%, and 2% than fish fed at the rate of 3% and 4%. Hematocrit (HCT) and hemoglobin (Hb) levels were increased by feeding pomegranate meal at the rate of 1% than the other groups, while fish fed the control diet displayed higher Hb and HCT levels than fish fed at the rate of 2%, 3%, and 4% (P <0.05). WBCs displayed significant differences among the groups and increased by increasing the level of pomegranate meal in the diet. The blood total protein was decreased in fish fed 2%, 3%, and 4% than fish fed at the rate of 0% and 1% of pomegranate meal. The glucose value displayed the highest level in fish fed at the rate of 3% of pomegranate meal than the other groups. The triglycerides were reduced by pomegranate meal at the rate of 2% than 3% and 4% without differences with the control and 1%. The blood total cholesterol was reduced in fish fed at the rate of 1% of pomegranate meal than the other groups (P <0.05). The blood IgM and complement components (C3 and C4) were increased by increasing the supplementation level of pomegranate meal with the highest value in fish fed at the rate of 3% (P <0.05). In conclusion, dietary pomegranate meal at the rate of 1% is recommended for enhancing the growth rate and health status of rainbow trout.