Effects of Pelleted Probiotic on Growth, Water Quality, and Disease Resistance in Pacific White Shrimp (Litopenaeus vannamei) in Static Biofloc Systems

Probiotics are increasingly used in aquaculture to improve growth and water quality and boost disease resistance in farmed species. This study investigated the application of various concentrations of a commercial probiotic (mix of Bacillus subtilis and B. licheniformis) added to culture water to evaluate its effects on growth performance, water quality, and resistance to Vibrio parahaemolyticus infection. Over a 9-week trial, Pacific white shrimp (1.20 ± 0.01 g; stocked at 160 shrimp m⁻³) were reared in static biofloc culture systems consisting of 24 independent 156 L circular black polyethylene tanks. Shrimp were subjected to various probiotic concentrations weekly (×4, ×8, and ×16 of the recommended dose, which was one pellet per 200 g of feed) as three treatments. The control group (×0), without any probiotic addition, was used as the fourth treatment. Each treatment had six replicate tanks and shrimp were provided a commercial diet (Zeigler Shrimp Grower SI-35, CP 35%) four times per day via hand feeding. Following 9 weeks of culture, probiotic addition did not significantly impact growth or water quality (besides significant dissolved oxygen (DO) and temperature variations), but improved disease resistance. During the disease challenge, survival in all probiotic treatments (×4, ×8, and ×16) was significantly higher (regardless of dose) than that of the control group (x0; p < 0.05). These results suggest that the commercial probiotic may enhance shrimp resilience against Vibrio spp. infections. These findings suggest that although growth or water quality improvements were not confirmed in this trial, this probiotic appears to positively affect disease resistance in shrimp against V. parahaemolyticus infection in biofloc systems.