Immunomodulatory and growth promotors effects of rosemary (Rosmarinus officinalis) and/or Spirulina with respect to some gene expression on Nile tilapia (Oreochromis niloticus) in Aswan Governorate

The purpose of this work trial was to determine the true impact of spirulina and rosemary in a combination treatment on Nile tilapia performance before experimental infection. Moreover, the effects of these treatments on the liver and kidney functions, the histology of certain organs, and the expression of certain antioxidant and immune-related genes in the liver tissue both before and after Aeromonas hydrophila (A. hydrophila) infection are also included. To achieve this purpose, four diets were prepared: the first was free of additives as a control group (Con), the second contained (SP) spirulina at 7.5 g/kg of diet, the third contained (RM) rosemary at a rate of 10 g/kg of diet, and the fourth one contained rosemary and spirulina as a SP + RM group. The results of the different parameters indicated the growth-stimulant effects of rosemary and spirulina either alone or in a combination when compared with the control group (P ≤ 0.05), with a superior effect to combination treatment. In addition, improved hematological parameters, immunological assays, phagocytic activity and index, and expression of antioxidant and immune-related genes occurred before and after infection. Moreover, there were positive effects of spirulina and rosemary without pathological lesions in the different organs before infection and fewer lesions after infection. •Dietary combination of spirulina and rosemary improves Nile tilapia growth.•Dietary combination of spirulina and rosemary increased gene expression.•Dietary combination of spirulina and rosemary increased resistance to experimental infection.