Application of Probiotics and Postbiotics in a Biofloc-Based Nursery System for Penaeus vannamei

Postbiotics are promising tools for improving shrimp production and health, but the effects of their direct application to culture water, particularly in biofloc technology (BFT) systems, remain poorly understood. This study evaluated the effects of commercial probiotic and postbiotic products on the performance of Pacific white shrimp (Penaeus vannamei) juveniles reared in a BFT nursery system. A total of 900 post-larvae (PL; initial weight: 13.00 ± 4.00 mg) were stocked in 12 experimental units for 32 days (75 PL unit−1). The experiment followed a completely randomized design with four experimental groups and three replicates: Control (without probiotic or postbiotic supplementation), Probiotic (0.5 mg L−1 day−1 probiotic powder), Postbiotic 1 (1.0 mg L−1 day−1), and Postbiotic 2 (2.0 mg L−1 day−1). At the end of the trial, shrimp reared with Postbiotic 2 supplementation had lower settleable solids concentrations than the control. Postbiotic 2 treatment resulted in higher final weight, lower apparent feed conversion ratio (FCR), and a higher Scaled Mass Index (SMI). In addition, shrimp from both postbiotic treatments exhibited greater antenna length and a higher proportion of granulocytes, suggesting changes in body condition and hemocyte composition, respectively. These findings suggest that postbiotic supplementation, particularly at 2 mg L−1 day−1, can contribute to settleable solids management and improve nursery growth performance and feed utilization in BFT systems.