Optimizing feed management of Pacific white shrimp (Litopenaeus vannamei) raised in biofloc and mixotrophic systems

Abstract

With the rapid growth of the global population and increasing demand for high-quality protein, shrimp aquaculture has intensified worldwide. This intensification is especially evident in Pacific white shrimp (Litopenaeus vannamei), which now represents the most widely cultured shrimp species. As production scales up, challenges related to feed costs, water quality deterioration, and disease outbreaks have become more pressing. Microbial-based systems, such as biofloc and mixotrophic systems, have emerged as promising solutions to these challenges, offering improved nutrient recycling, reduced water use, and enhanced biosecurity. These systems rely on complex microbial communities that convert waste nutrients into consumable floc for culture animals while simultaneously improving water quality. To explore how these systems can be optimized through improved feed management, four independent studies were conducted to assess the impacts of stocking density, protein level and feeding ration, probiotic supplementation, and compensatory growth strategies on shrimp performance, water quality, and disease resistance. The first study focused on determining the optimal stocking densities for Pacific white shrimp in both indoor biofloc and outdoor mixotrophic recirculating systems. The aim was to evaluate how different stocking densities affect shrimp growth performance. In the indoor biofloc trial, shrimp were stocked at eight densities ranging from 67 to 533 shrimp/m³ and reared for 30 days. In the outdoor mixotrophic system, five stocking densities from 50 to 400 shrimp/m³ were tested over eight weeks. Results indicated that higher stocking densities increased total biomass yield in both systems but resulted in decreased individual growth, higher FCRs, and, in the mixotrophic system, reduced survival. In contrast, survival remained stable across densities in the biofloc system. These findings demonstrated that while higher densities may maximize yield, they can negatively impact shrimp performance and system stability if not properly managed. The second study addressed the interaction between dietary protein levels and feeding rations in a biofloc environment. Protein is a major cost component in aquafeeds, and optimizing its inclusion is key to maintaining economic and environmental sustainability. Four diets ranging from 25% to 40% crude protein were tested in combination with different feeding rations to match protein inputs across treatments. Results revealed that shrimp fed moderate protein levels (30-35%) with properly adjusted rations achieved growth comparable to those fed higher protein diets. Additionally, moderate protein treatments showed improved nutrient retention and reduced feed costs. Water quality remained within acceptable ranges, and no adverse effects were observed. These results suggest that biofloc systems can partially offset dietary protein requirements through microbial supplementation, making protein optimization a viable strategy for sustainable intensification. In the third study, the role of probiotic supplementation was examined in the context of biofloc systems. Disease outbreaks, particularly those caused by bacterial pathogens such as Vibrio parahaemolyticus, represent a major threat to shrimp aquaculture. Probiotics have been proposed as a sustainable alternative to antibiotics, with benefits ranging from improved gut health and digestion to pathogen inhibition and immune enhancement. In this trial, shrimp were raised in a static biofloc system and treated with pelleted probiotics addition to culture water at varying concentrations. After the culture period, a pathogen challenge was conducted to assess resistance. While no significant improvements in growth or water quality were observed in this study, probiotic-treated shrimp showed lower cumulative mortality following bacterial challenge. These findings support the use of probiotics as a disease management tool, particularly where disease outbreaks are a concern. The fourth and final study investigated compensatory growth in Pacific white shrimp subjected to restrictive feeding regimes within a biofloc system. Compensatory growth refers to an accelerated growth response following a period of feed restriction and has been proposed as a strategy to improve feed efficiency and reduce production costs. In this experiment, shrimp were assigned to feeding schedules with different numbers of feed restriction days per week (1-3 days) and different rations over a 7-week trial. Growth performance, feed efficiency, apparent protein and energy retention, and survival were evaluated. Shrimp that experienced moderate restriction (1-2 days/week) exhibited partial compensatory growth, maintaining comparable final weights and improved feed efficiency relative to fully fed controls. However, excessive restriction (3 days/week) led to reduced performance. These results suggest that biofloc systems, with their nutrient-rich microbial flocs, can help mitigate the impacts of temporary feed deprivation up to some extent, allowing producers to implement strategic feed restriction with minute effect on the performance. Together, these four studies provide an integrated understanding of how feed management practices can be tailored to maximize productivity and sustainability in biofloc and mixotrophic shrimp farming systems. The findings offer critical insights into the complex interplay between nutrition, microbial ecology, and animal performance in intensive recirculating aquaculture. Importantly, this research contributes to the development of practical strategies that reduce feed costs, maintain optimal water quality, and enhance disease resistance, ultimately supporting more sustainable, profitable, and resilient shrimp aquaculture operations capable of meeting global food demands under intensifying production and environmental constraints.