Lactobacillus salivarius Probiotic Supplementation Modulates Gut Function, Improves Growth, and Meat Quality in Tropical Whiteleg Shrimp

Probiotics are increasingly incorporated into shrimp aquaculture, yet the comparative efficacy of single‑strain versus mixed‑strain formulations remains insufficiently defined, particularly in relation to gut microbiome remodeling, intestinal architecture, and proteomic determinants of meat quality. A 90‑day randomized grow‑out trial was conducted under semi‑intensive conditions using Litopenaeus vannamei fed three diets (triplicate ponds per treatment): basal diet (W), basal diet plus mixed‑strain EM probiotic (T), and basal diet plus Lactobacillus salivarius GZPH2 (H). Growth performance, survival, intestinal histology, microbiota composition and function (16S/18S rRNA sequencing), and meat quality (4D‑DIA proteomics) were evaluated. Both probiotics improved growth and feed utilization relative to controls, but H consistently outperformed T in survival (83.0% vs. 81.0%), meat yield (6.53% vs. 4.84%), lipid deposition (4.05% vs. 3.39%), and mineral enrichment (Fe, Se; Zn/Cu ratio: 2.27 vs. 1.97). H enhanced microbial α‑diversity and enriched metabolically versatile taxa ( Achromobacter , Pedobacter , Photobacterium , and Labrenzia ), whereas T produced Bacillus ‑dominant communities (~85%) with reduced diversity. Intestinal morphology showed greater absorptive expansion in H (+14.10%) and higher goblet cell density in T (+51.21%). Functional profiling indicated that H activated KEGG pathways related to amino acid transport, nitrogen metabolism, fatty acid biosynthesis, and trace‑mineral transport, supporting enhanced protein turnover, lipid deposition, mineral assimilation, and redox‑homeostasis. In contrast, T favored carbohydrate metabolism and antimicrobial gene expression, promoting competitive exclusion but limiting metabolic versatility. Proteomic analysis identified 183 differentially expressed proteins (DEPs, 110 upregulated in H; 73 in T). H upregulated myofibrillar and antioxidant proteins, including myosin heavy chain type 2, hemocyanin, catalase, metallothionein, and selenium‑binding protein, while suppressing proteolytic and glycolytic enzymes, thereby improving texture, oxidative stability, and nutritional value of meat. Collectively, Lactobacillus salivarius GZPH2 demonstrated superior capacity for metabolic modulation, intestinal remodeling, and proteomic enhancement, highlighting its potential as a targeted probiotic for optimizing shrimp health and meat quality in aquaculture nutrition.