Abstract
The current study aimed to clarify the role of phycocyanin that is extracted in Spirulina platensis and used as a feed supplement in Nile tilapia feed. The parameters of growth, biochemical indices and immunological responses were examined; an experiment was carried out on juvenile Nile tilapia, in which a design was applied that consisted of four treatment groups and each group was triplicated. Five different diets were made, and the diets contained a control diet (pc0) and four diets (pc0.5gm, pc1gm, ec3gm and ec5gm) with the phycocyanin concentrations of 0.5, 1,3 and 5gm/100gm/feed. A group of 150 fingerlings, initially having an average of 10.4 0.47g, was randomly subjected to a 90-day feeding experiment of 15 tanks. After the study was completed, fish with the highest level of supplement (Pc5gm) had significantly better growth performance in terms of body weight gain which was better and with the highest ratios of feed to weight (FCR). The addition of phycocyanin resulted in a significant increase in serum total protein as well as marked decreases in hepatic enzymes (AST, ALT), and cortisol and thus demonstrates the improved functioning of the liver and suppressed physiological stress. In addition, the signs of oxidative stress were positively altered, and reduced malondialdehyde (MDA) and increased activity of antioxidant enzymes, specially superoxide dismutase (SOD), and nitric oxide (NO). Phycocyanin Stimulating immune response was also significantly high among the phycocyanin-treated animals in terms of the presence of lysozyme activity, presence of IgG and IgM. In line with this, the capacity of S. platensis derived phycocyanin as a sensible feed additive in the aquaculture industry is highlighted; the addition not only leads to growth but also improves immune response and antioxidant defenses in Nile tilapia, with no adverse effects being reported to occur with its inclusion in the experimental environment.

Key words: Phycocyanin Extraction, Spirulina platensis, Nile tilapia, Growth Performance, Biochemical.