Integrated commercial and low-fishmeal fermented feed boosts survival and modulates intestinal microbiota in pacific white shrimp ().

The objective of this study was to evaluate the impact of using a combination of fermented feed and commercial feed on the survival and intestinal microbiota of shrimp. In this study, a superior microbial community comprising , , , and was found based on the improvement in nutritional quality metrics ( < 0.05). Using this community, a low fish meal (LFM, 15%) shrimp fermented feed was prepared. Subsequently, a 56-day feeding trial was conducted, involving a total of approximately 100,000 individual shrimp. The shrimp were divided into 2 treatments, the control group was administered a high fish meal (30%) non-fermented diet (NFD), while the treatment group received a mixed diet (MFD) with a 2:3 fermented to non-fermented ratio. Results showed that feeding the diet MFD improved the shrimp survival ( = 0.002) but reduced yield ( = 0.032) and weight gain ( = 0.003). In the first 29 days of the feeding trial, there was no statistical difference between the groups in metrics, namely ammonia nitrogen, nitrite, pH, and total alkalinity ( > 0.05). During the last 27 days, feeding the MFD diet did not increase ammonia nitrogen or nitrite content in water ( > 0.05), and even reduced these parameters at specific sampling intervals. Similarly, water pH and total alkalinity in the MFD group showed significant elevations at particular sampling points ( < 0.05). and (common pathogenic bacteria in shrimp culture) demonstrated no population increase in water from shrimp fed the MFD diet, with significant decreases observed at specific time points compared to the NFD group ( < 0.05). Feeding the MFD modulated the features of the intestinal microbiota manifested by marked reductions in alpha-diversity indices including the observed_OTUs ( < 0.001), Chao1( < 0.001), Shannon ( < 0.001), and Simpson ( < 0.001) indexes. Concurrently, this nutritional modulation drove a phylum-level taxonomic shift characterized by increased Proteobacteria relative abundance and decreased that of Bacteroidetes ( < 0.001). The MFD group also exhibited a notably increased ratio of Firmicutes to Bacteroidetes ( = 0.016). Additionally, the linear discriminant analysis effect size analysis revealed that Proteobacteria and Bacteroidetes served as potential biomarkers of the MFD and NFD groups at the phylum level, respectively, with Marinicellaceae and Flavobacteriaceae distinguishing them at the family level. The gut microbiota of shrimp on two feeding diets showed distinct patterns in the predicted pathways related to immune and infectious disease, with diets also affecting their phenotypic traits. Overall, combined commercial and fermented feed improved survival and modulated intestinal microbiota in . .