Comparative study on the effect of dietary β-carotene and phycocyanin extracted from Spirulina platensis on immune-oxidative stress biomarkers, genes expression and intestinal enzymes, serum biochemical in Nile tilapia, Oreochromis niloticus.

The current trial investigated the roles of β-carotene and phycocyanin extracted from Spirulina platensis on growth, serum biochemical, digestive enzymes, antioxidant defense, immune responses, and immune gene expression in Nile tilapia (Oreochromis niloticus). Fish (1.52 ± 0.10 g) were randomly stocked to three treatments with three replicates (12 fish per replicate) in nine aquaria (60 L glass aquarium for each), and reared for 70-days. Three tested diets were formulated to be isonitrogenous and isolipidic, and were offered for experimental fish until ad-libitum three times daily at 09:00 a.m., 11.00 a.m. and 3:00 p.m. The first diet (control) was without supplementation. About 50 mg β-carotene and 50 mg phycocyanin kg-1 were supplemented to the other experimental diets, respectively. Results indicated that feed intake was not (P > 0.05) differ among experimental diets. Compared to control diet wight gain and specific growth rate were significantly (P < 0.05) in fish fed diet containing β-carotene, while, the highest weight gain and the best FCR were detected in phycocyanin diet. Survival fish among treatments was significantly (P < 0.05) differ and the highest survival rate was showed in fish fed diet supplemented with phycocyanin. Either β-carotene or phycocyanin significantly (P < 0.05) improved the intestinal digestive enzymes compared with control diet, where the highest values of chymotrypsin, trypsin, lipase and amylase were noticed in fish fed phycocyanin. Diets supplemented with β-carotene and phycocyanin significantly (P < 0.05) improved hematology parameters contents compared with to the control diet, and the best contents were detected in fish fed diet supplemented with phycocyanin. The highest significant (P < 0.05) phagocytic, lysozyme, immunoglobulin M (IgM), superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and total antioxidant capacity (T-AOC) activities were recorded in diet supplemented with phycocyanin. The transcripts of interferon gamma and interleukin 1β genes were (P < 0.05) up-regulated in the liver of fish fed diet supplemented with β-carotene and phycocyanin, but expression of HSP70 gene down-regulated in fish fed β-carotene and phycocyanin containing diet compared control. The highest gene expression of the interferon gamma and interleukin 1β was observed in fish fed phycocyanin.