Effects of dietary pomegranate peel meal on the growth performance, blood indices, and innate immune response of rainbow trout (Oncorhynchus mykiss)

The present study aimed at evaluating the influences of pomegranate peel meal on the growth performance, hematology, and blood biochemistry of rainbow trout. Fish were fed 5 varying levels of pomegranate peel meal (0%, 1%, 2 %, 3%, and 4%) for 60 days. The obtained results showed that weight gain was significantly higher in fish fed at the rate of 1% than the other groups, while specific growth rate (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, feed conversion ratio 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% in relation to the control without differences with the other groups (P<0.05). Red blood cells 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 and hemoglobin levels were increased by feeding pomegranate meal at the rate of 1% compared to 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). White blood cells 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% compared to 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 compared to 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 compared to 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.