Supplementation of multi-strain probiotics in water enhances growth, metabolic responses, immune function, growth and immunity genes, and disease resistance in Nile tilapia (Oreochromis niloticus)
摘要
Although probiotics have demonstrated various advantages in aquaculture, their capacity to improve Nile tilapia (Oreochromis niloticus) growth, blood health, and resilience against Aeromonas sobria infection remains incompletely understood. Therefore, this experiment was designed to assess the impact of a multi-strain probiotic (AQUA CLEAR-S®; AC) on growth indices, water quality, feed conversion efficiency, physio-metabolic responses, hematological variables, the expression of genes associated with growth and immunity, and disease resistance to A. sobria infection in Nile tilapia. One hundred and forty-four Nile tilapia with a mean initial weight of 18.05 ± 0.1 g were randomly allocated to four experimental groups to evaluate the effects of water supplemented with a multi-strain probiotic (AQUA CLEAR-S®; AC) at concentrations of 0 (AC0), 0.1 (AC0.1), 0.2 (AC0.2), or 0.3 (AC0.3) g/m3 over a 70-day period. Fish were randomly distributed among twelve 120-L glass aquaria at a stocking density of 12 fish per aquarium/m3. The AC probiotic consisted of Lactobacillus acidophilus (9.8 × 1011 CFU), Bacillus subtilis (10 × 1011 CFU), Bacillus licheniformis (7 × 1011 CFU), and Saccharomyces cerevisiae (9 × 1011 CFU). Regarding water quality, the AC0.2 and AC0.3 treatments resulted in significantly lower dissolved oxygen (DO) and pH values (P < 0.05) than the AC0 group. Notably, these treatments also led to a significant decrease in total ammonia nitrogen (TAN) and ammonia (NH3) levels (P < 0.05). Furthermore, significant enhancements in hematological parameters and growth indices were observed in fish of the AC0.2 and AC0.3 groups (P < 0.05). Notably, all AC-supplemented groups showed significantly diminished liver enzyme activities and lipid profile values when compared to the AC0 group (P < 0.05). Supplementation with the multi-strain probiotic (AC) significantly improved the immune response, as evidenced by the lowest mortality rate in the 0.3 g AC/m3 treatment (P < 0.05). Furthermore, AC administration led to the upregulation of genes associated with growth (GH and IGF-1) and immunity (TNF-α and IL-1β). Following challenge with A. sobria, the cumulative mortality rates were 50%, 35%, and 30% in the AC0.1, AC0.2, and AC0.3 groups, respectively, compared to 70% in the control group. This study strongly indicates that a multi-strain probiotic (0.2 or 0.3 g AC/m3) elicits beneficial effects on a wide array of critical factors in Nile tilapia. These include significant enhancements in growth performance, feed conversion ratio, physiological and biochemical profiles, water quality, immune modulation, the expression of growth-related genes, and survival following challenge with Aeromonas sobria.
Graphical Abstract