Dietary administration of gelatinised polyhydroxybutyrate to Penaeus vannamei improved growth performance and enhanced immune response against Vibrio parahaemolyticus

Abstract

The effect of dietary supplementate, gelatinized polyhydroxy butyrate on the growth performance, and prophylactic disease control in Penaeus vannamei was evaluated. Healthy juvenile shrimp were collected from farms, acclimatized in a laboratory aquarium and fed gelatinized polyhydroxybutyrate (PHB) diet for 60 days. Infectivity experiments were conducted with Vibrio parahaemolyticus SF14 which was isolated from diseased shrimp samples. The treated, control and challenged shrimp samples were analyzed for intestinal function, immune enzymes, and histopathological changes. The PHB treated shrimp showed significant weight gain (7.81 ± 0.184 g) compared to the commercial diet fed control shrimp (5.914 ± 0.070 g) at 5% significant level. The activity of immune enzymes such as prophenol oxidase and superoxide dismutase activity along with the total antioxidant activity significantly elevated in the PHB diet fed shrimp. The digestive enzyme levels were found to be higher in the PHB treated shrimp indicates the PHB modulates digestive function in shrimp. The V. parahaemolyticus SF14 challenge resulted in 100% mortality in the control shrimp whereas the PHB diet fed shrimp were completely protected with 100% survival against V. parahaemolyticus infection. A histopathological examination revealed that shrimp fed with the commercial diet and challenged with V. parahaemolyticus displayed necrotic muscles and vacuolation in the muscle fibers along with hemocyte infiltration in the gills. In contrast, the shrimp fed PHB diet and challenged with V. parahaemolyticus showed no pathological changes in the muscle fibers and gills. Cumulatively, this study demonstrated that dietary supplementation of 1% gelatinized PHB effectively protects shrimp against infective pathogens and improves their immune function and growth rate.