Combined Animal and Plant Protein Enable High Fishmeal Replacement in Penaeus vannamei Under Biofloc Technology

The increasing demand and limited availability of fishmeal (FM) have intensified the need for sustainable alternative protein sources in shrimp aquafeeds. This study evaluated high FM replacement in juvenile Penaeus vannamei reared under biofloc technology (BFT), integrating in vitro protein digestibility, growth performance, nutrient utilization and microbiome analyses. Six isoproteic and isolipidic diets combined two FM levels (0% and 7.5%) with animal (A), plant (P), or mixed (AP) protein sources, plus a 15% FM Control diet were assayed. Plant-based diets showed higher in vitro protein digestibility and amino acid release than animal-based diets. However, these differences were not reflected in shrimp performance, as final body weight, SGR and survival were similar among dietary treatments. Apparent feed conversion ratio, protein efficiency, and economic performance were improved in shrimp fed the A7.5 and AP7.5 diets, whereas complete FM replacement resulted in poorer performance. Biofloc and shrimp intestinal microbial community composition was primarily driven by temporal succession, whereas dietary protein source modulated the abundance of specific bacterial families. Biofloc and intestinal communities shared limited taxonomic overlap at the family level, suggesting restricted microbial exchange together with strong habitat and host mediated selection. Overall, these findings indicate that a diet containing 7.5% fishmeal (FM), supplemented with either animal-derived proteins or a combination of animal- and plant-derived protein sources, represents an optimal strategy for juvenile Penaeus vannamei cultured under BFT conditions, maintaining performance while preserving intestinal microbial stability and health.