Probiotics and <i>Spirulina platensis</i> Improved Growth Performance of Nile Tilapia ( <i>Oreochromis niloticus</i> ) by Upgrading Intestinal Morphology and Activating GH/IGF Axis

Probiotics and spirulina are used to improve health, growth, and immunity of fish. The purpose of this study was to evaluate the effects of water additive probiotics and dietary Spirulina platensis on growth (weight gain (WG) and specific growth rate (SGR)), hematobiochemical parameters (hemoglobin (Hb) and blood glucose (Glu)), intestinal histology, and genes (growth hormone ( gh ) in pituitary and insulin‐like growth factors: igf-1 and igf-2 in liver) expression profiles of Nile tilapia ( Oreochromis niloticus ). Nile tilapia was distributed to three treatment groups: Control (no probiotics or spirulina), Probiotic (probiotics 1.0 mL/L in water), and Spirulina ( Spirulina platensis , 50 g/kg feed), each with three replicates for 42 days. Fish supplemented with probiotic and spirulina exhibited significantly higher ( p &lt; 0.05) WG (21.66 ± 2.92 g and 25.63 ± 3.92 g, respectively) and SGR (2.30 ± 0.16 and 2.18 ± 0.14%/day, respectively) than the control group. Hb and blood Glu levels showed negligible variation ( p &gt; 0.05) among the groups. The abundance of mucus producing goblet cells (GCs) was highest in fish reared with probiotic and spirulina treatments compared to the control group. Relative mRNA levels of gh in the pituitary were expressed profoundly ( p &lt; 0.05) in fish reared with probiotics and spirulina treatments compared to the control group. Relative mRNA levels of igf-1 in the liver expressed significantly higher ( p &lt; 0.05) in the fish fed with spirulina, whereas the relative mRNA levels of igf-2 expressed significantly higher ( p &lt; 0.05) in the fish subjected to probiotic treatment than control group. Principal component analysis (PCA) also supported the influence of probiotic and spirulina regarding growth performance over control treatment. These findings showed that probiotic and spirulina positively affect growth by improving intestine morphology and activating the GH/IGF axis in Nile tilapia.