Impact of Spirulina platensis as a Dietary Supplement on Growth Performance, Blood Biochemical Parameters, and Expression of Growth-Related Genes in Nile Tilapia (Oreochromis niloticus)

THE present investigation was designed to verify the effect of using Spirulina platensis (Sp) on growth performance, blood biochemical parameters, and expressions of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor1 (IGF-1), insulin-like growth factor 2 (IGF-2), and myostatin (MSTN) genes in Nile tilapia. A total of 96 fingerlings (12 +/- 0.2 g) were randomly allocated into eight groups, each containing 12 fish, and fed diets containing 0%, 1% (10 g), 2% (20 g), and 3% (30 g) SP/kg for 8 weeks. Significant improvements in growth were observed in the 1% SP group, with the best feed conversion rate at 1.09. Biochemical parameters, including serum protein, globulin, liver enzymes (ALT and AST), cholesterol, and glucose concentrations, were analyzed using a spectrophotometer for calorimetric analysis. Higher serum protein and globulin levels were observed in the 1% SP group compared to the control. RT-PCR analysis indicated elevated GH expression in the brain and muscles, along with increased IGF-1 and IGF-2 levels observed in the liver and muscle tissues of the 1% SP group compared to the control and other treatments. However, there was a positive correlation between the 1% SP diet and enhanced MSTN mRNA levels in muscle tissues. Except for higher ether extract (EE) in the 2% SP treatment, there were no significant changes in fish survival or body composition. Overall, this study recommends utilizing 1% SP as a dietary supplement to improve growth, feed utilization, biochemical parameters, and growth-related gene expressions in Nile tilapia.