Dietary poly-β-hydroxybutyrate improved the growth, non-specific immunity, digestive enzyme activity, intestinal morphology, phagocytic activity and disease resistance against Vibrio parahaemolyticus of Pacific white shrimp, Penaeus vannamei

Abstract This study assessed the effects of dietary supplementation of poly-β-hydroxybutyrate (PHB) on growth performance, feed efficiency, non-specific immunity, digestive enzyme capacity, phagocytic activity, hemocyte count, intestinal morphology and disease resistance against Vibrio parahaemolyticus of Pacific white shrimp (Penaeus vannamei). Six diets were prepared by supplementing graded levels of PHB at 0.00, 0.25, 0.50, 1.00, 2.00 and 4.00% (Con, P0.25, P0.5, P1.0, P2.0 and P4.0, respectively). Triplicate groups of 25 shrimps (initial body weight: 0.25 ± 0.01 g) per treatment were randomly assigned and fed an experimental diet for 56 days. Growth performance of shrimp was significantly improved by 1% dietary PHB supplementation. PHB-included diets fed shrimp showed significantly improved hepatopancreatic trypsin, chymotrypsin and pepsin activities. Villus height was significantly increased with dietary PHB supplementation and villus width was increased at a 1% inclusion level. P0.25, P0.5 and P4.0 groups significantly increased phenoloxidase activity and the P2.0 group significantly increased anti-protease activity compared to that in Con group. The survival of shrimp challenged against V. parahaemolyticus were higher in P0.5, P1.0 and P2.0 groups than in the Con diet. According to the above observations, the optimal dietary PHB supplementation level for maximum weight gain would be 1% for Pacific white shrimp.