Abstract
Background:
Numerous natural phytobiotic products are uusedas feed additives to enhance fish performance, quality, and immunity.

Aim:
This study evaluated the effect of a natural phytobiotics mixture (Syrena Boost “SB”) on growth performance, intestine health, immune-oxidative status, and hemato-biochemical parameters of fingerlings (Oreochromis niloticus).

Methods:
Fish (n = 4800, average initial weight = 1.247±0.047g) were randomly distributed in 12 aquatic compartments with a total water volume of 2 m3 (2×1×1 m) for each one, representing four groups, in triplicate: control group (CG), SB1, SB2, and SB3, in which fish received a basal diet (30/6, protein/lipid ratio) containing 0, 0.1, 0.2, 0.4 g kg−1 SB respectively for 60 days.

Results:
The results showed a significant (p < 0.05) improvement in fish performance (survival rate, specific growth rate, weight gain, final weight, and feed conversion ratio) and intestine histomorphology (increased goblet cell number, intestinal villi length, but inter-villi space, decreased) in fish that received SB1, SB2, and SB3 compared with CG (p < 0.05) with the most favorable outcomes observed in treatment supplemented with SB2. Dietary inclusion of Syrena Boost “SB” at different doses (SB1, SB2, and SB3) improved certain blood hematological parameters, including globulin and total protein, while decreasing aspartate aminotransferase, alanine aminotransferase, cholesterol, triglycerides, glucose, and albumin compared with CG (p < 0.05), with the most favorable outcomes observed in SB2. The fish showed improvements in digestive enzymes (lipase and amylase), antioxidant enzymes (increased catalase, superoxide dismutase), as well as a reduction in malondialdehyde, as well as showed improvement in the immunity health indicators (phagocytic index, phagocytic activity, and lysozyme activity), and gene expression [glutathione peroxidase (GPX), and catalase (CAT), tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), insulin-like growth factor (IGF), interleukin-8 (IL-8) and growth hormone receptor (GH)] when they received SB1, SB2, and SB3 supplemented diets, with the most favorable outcomes observed in SB2 compared with CG (p < 0.05). Thus, the Syrena Boost “SB” at 0.2 g kg−1 diet (SB2) can be used effectively in Tilapia diets to improve growth, intestinal health, blood health, oxidative status, and immune-related gene expression.

Conclusion:
Dietary supplementation with a natural phytobiotic mixture (Syrena Boost®) improved fish performance, intestine health, and the immune-physiological status of Nile tilapia fingerlings. The best findings in this experiment were observed in fish that received SB2.

Key words: Immune-physiological response, Gene expression, Growth performance, Nile tilapia, Phytobiotics