Gut Microbiota deliverables: reflecting the Efficacy of Dietary Probiotic Supplementation for Growth and Feed Utilization in <i>Litopenaeus vannamei</i> Towards Sustainable Aquaculture

The growing demand for sustainable aquaculture requires improvements in shrimp production efficiency and health management. This study investigated the effects of dietary Bacillus subtilis and Lactobacillus acidophilus supplementation on the gut microbiota dynamics, growth performance, survival, and feed utilization of the Pacific white shrimp ( Litopenaeus vannamei ) post-larvae. Shrimp were reared over 84 days under four experimental groups: control (a probiotic-free diet), supplemented with 10⁷ CFU/g Lactobacillus (L), 10⁷ CFU/g Bacillus (B), and a mixed probiotic treatment (M) with 0.5x10⁷ CFU/g per each. Growth metrics, survival rate and, feed utilization were assessed, and entire intestinal samples were analyzed using high throughput DNA sequencing of V1-V9 of 16S rRNA hypervariable regions. Bacillus supplementation significantly improved final body weight and specific growth rate (SGR) compared to the other groups (p &lt; 0.05), leading to notably higher biomass by Day 74. However, by the end of the 84-day experiment, these significant differences in body weight and length were no longer observed among the treatment groups (p &gt; 0.05). The mixed probiotic group demonstrated significantly better FCR than the Bacillus group (p &lt; 0.05), indicating improved feed efficiency. Gut microbiota analysis showed dominance of Pseudomonadota at the phylum level and Vibrio at the genus level (18.06%–48.28%). Neither alpha nor beta diversity was significantly affected by probiotic treatments (p &gt; 0.05), though temporal and treatment-specific shifts in bacterial composition were detected. These results suggest that Bacillus and mixed probiotic supplementation may enhance shrimp growth and feed efficiency, supporting their potential application in sustainable shrimp farming.