Enhancing growth performance, antioxidant defense, immunity response, and resistance against heat stress in Nile Tilapia (Oreochromis niloticus) fed Saccharomyces boulardii and/or Bifidobacterium bifidum

This study evaluated the benefits of supplementing Nile tilapia diets with probiotics Saccharomyces boulardii (SB) and Bifidobacterium bifidum (BB) in terms of growth, antioxidant status, immune-related genes, and resistance against heat stress. Fish (with an initial weight of 3.85 ± 0.50 g) organized into four triplicate treatment groups defined as control (T0, no supplementation), Saccharomyces boulardii (T1, 10 10 CFU/g), Bifidobacterium bifidum (T2, 1.5×10 8 CFU/ mL) and a mixture of both (T3). This trial continued over a 56-day feeding period and fish were sampled for analysis and thereafter, Nile tilapia was exposed to heat shock under a high temperature of 32°C for 48 hours. Results revealed that the highest final weight (FW), weight gain (WG), and specific growth rate (SGR) as well as significantly lower feed conversion ratio (FCR) were observed in the T3 compared to other groups (P < 0.05). Alternative complement activity (ACH50), total Protein (TP), and lysozyme (LZM) improved in fish-fed supplemented diets, and the highest value was observed in T2 and T3 (P < 0.05). Moreover, this combination enhanced antioxidant status, as evidenced by elevated levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT), reflecting improved defense against oxidative stress (P < 0.05). Gene expression analyses revealed increased expression of immune-related genes such as Interleukin 8, Interleukin10, Interleukin1β, tumor necrosis factor, and LYZ as well as antioxidant genes including CAT, Gpx, glutathione-disulfide reductase, SOD, in test groups compared to the control group (P < 0.05). The survival rate in Nile tilapia after heat stress was significantly higher in T3 compared to other groups (P < 0.05). It was concluded from this experiment that dietary inclusion of the probiotics species in combination could be promote growth and immune responses of O. niloticus . • S . boulardii and B. bifidum increased growth in Nile tilapia. • S. boulardii and B. bifidum improved innate immune, antioxidant parameters, and their related genes in Nile tilapia. • Fish were fed with S. boulardii and B. bifidum displayed enhanced resistance against heat stress.