Diet-Independent Positive Effects of a Multi-Species Probiotic on the Growth Performance and Resistance against Vibrio parahaemolyticus in White Leg Shrimp

SIMPLE SUMMARY: The aquaculture industry is facing several challenges, including water quality, stocking density and disease outbreaks due to bacterial pathogens. Pathogens and challenging conditions in aquaculture are common problems that cause mortality, reduce growth performance and consequently lead to high economic losses. To prevent those losses, antibiotics are often used for treatment or prophylaxis. With the increasing concern for antibiotic resistance and the demand to reduce the application of antibiotics, alternative solutions are needed. Incorporating probiotics in the diet can be one of the solutions to support feed efficiency as well as the resilience of the animals to pathogen pressure. The results of two experiments demonstrate that probiotic feed additives are promising strategies to improve shrimp production and provide increased protection against bacterial infection, independent of the diet formulation. ABSTRACT: Probiotic feed additives can support the gut health of shrimp and thereby improve performance, production efficiency and disease resistance. Two experiments in white leg shrimp aimed to investigate the effects of a multi-species probiotic feed supplement (AquaStar(®), 3 g/kg feed, Biomin GmbH, Getzersdorf, Austria) in feed formulations with different marine meal levels (32% and 15%) on growth performance and resistance against Vibrio parahaemolyticus. Juvenile shrimp were stocked in a recirculating aquaculture tank system at a density of 20 shrimp/46.8 L and were fed diets with and without the probiotic supplementation for 8 weeks. Afterwards, a bath immersion with V. parahaemolyticus was performed and mortality was observed over a period of 14 days. Independent of the diet formulation, probiotic supplementation significantly improved the survival rate of the shrimp and the specific growth rate while decreasing feed consumption and feed conversion ratio when compared to the control (p ≤ 0.042). After the Vibrio immersion challenge, mortality was significantly decreased by 13.33% with probiotic supplementation in the high marine meal diet experiment (p = 0.042) and numerically decreased by 11.67% in the low marine meal diet experiment (p = 0.133). Overall, the results suggest that the beneficial effects of the probiotic can occur independently of the diet formulation.