RESUMO
Nile tilapia (Oreochromis niloticus) is the most common aquaculture fish, but is exposed to various pollutants and may be susceptible to infectious diseases due to reduction in their antioxidant status and immune defense. Therefore, researchers have tried to find feed supplements of natural origin to increase the health status of fish and decrease the incidence of drug resistance. The current study was conducted to investigate the effect of dietary supplementation of Miswak (Salvadora persica, SP) on Nile tilapia. Fish were randomly allocated into four experimental groups (30 fish each); the control fish were fed on the basal commercial diet and the SP-treated groups were fed basal diet supplemented with different concentrations 0.5, 1, and 2% for 30 days. The SP supplementations had no significant effects of SP on fish growth performance traits and lipid profiles but augmented the serum protein and globulin levels. The SP significantly improved the hepatic antioxidant status through the significant decrease of malondialdehyde (MDA) and the increases of reduced glutathione (GSH) levels and the activities of total superoxide dismutase (T.SOD), catalase (CAT) and glutathione peroxidase (GPx), especially in the SP 1% group, while glutathione S-transferase (GST) activities were significantly increased due to SP in a dose-dependent manner. The same results were obtained for the mRNA expression of CAT and GPx. Regarding the nonspecific immune status of the fish kidneys, SP, especially SP1, significantly increased interleukin-1 beta (IL-1ß) and interferon-gamma (INF-γ). The data of the present study revealed the protective effect of SP on Nile tilapia health status. Therefore, SP can be considered as a promising feed additive for Nile tilapia.