Pathogens, environmental stressors and opportunistic diseases are ubiquitous in aquaculture. Achieving efficient and profitable production, especially with the increasing global threat of antimicrobial resistance, is critical for producers. Helping aquaculture species to better perform with infectious and physiological pressures is therefore of high interest and a focus of research.
Cardozo et al., 20183 compared in vitro bacterial aggregation capacity of inactivated Pichia guilliermondii (Pg) and Saccharomyces cerevisiae (Sc), with Mannose as the positive control. Pg demonstrated twice the aggregation capacity at all commercial dosages compared to that of Sc (Fig 1). Pathogen aggregation is critical in innate immunity and homeostasis.
To assess the bacterial aggregation capacity of Pg in vivo, a bacterial clearance study was performed: Litopenaeus vannamei shrimp were injected with Vibrio harveyi. Three hours post-injection, V. harveyi concentration in hemolymph in the Pg fed shrimp was more than 3 times lower compared to control-fed shrimp (Fig 2). It was also shown that the granular hemocyte concentration in hemolymph was 56% higher after 4 weeks in Pg fed shrimp compared to that in control shrimp. (Fig 3) . Granular hemocytes are key for an effective and rapid immune response in shrimp, and represent an ideal parameter in monitoring shrimp immune potency.
In order to confirm the potential benefit of Pg in shrimp culture conditions, 2 challenge studies were performed in L. vannamei shrimp supplemented with 0.1% Pg4: Survival of shrimp 5 weeks after White Spot Syndrome Virus challenge increased by 84% compared to unsupplemented control shrimp, whereas it was 76% higher 5 weeks after Vibrio parahaemolyticus challenge. In field conditions without specific pathogenic challenge, vannamei shrimp fed with 0.1% Pg showed significant 10% increased growth compared to control at the end of a 7 week trial.
Inactivated whole yeast Pichia guilliermondii feed supplementation offers unique traits for use in shrimp culture and daily management, improving growth while significantly helping the shrimp to better cope with physiological and disease stress.