Daphnia similis
chitin and its derivative
chitosan were prepared as
immunostimulants to boost the immune response and determine the ability to control
infectious disease caused by Vibrio alginolyticus in white shrimp, Litopenaeus vannamei. Three experimental diets supplemented with 0%
chitin or
chitosan (control) and 0.4%
chitin or 0.4%
chitosan were fed to shrimp for 56 days. Dietary inclusion of 0.4%
chitosan accelerated shrimp growth compared to
chitin and control. The survival and
disease resistance of shrimp increased significantly when fed
chitin and
chitosan diets, after pathogenic injection, as indicated by the up-regulated immune responses in respiratory burst (RB),
superoxide dismutase (SOD), and phagocytic activity (PA). There were no significant differences in the total haemocyte count (
THC),
phenoloxidase (PO)activity, and
lysozyme (LYZ) activity among the groups. No significant differences were observed for
prophenoloxidase system-related gene expressions among groups. However, shrimp fed
chitin, and
chitosan expressed significantly higher levels of antimicrobial
proteins (penaeidin 3a,
crustin, and anti-
lipopolysaccharide factor 2) in the haemocytes than in control. The gene expressions of
catalase and
heat shock protein 70 increased in the hepatopancreas of shrimp fed
chitosan diet compared to the
chitin and control diet. The
O-linked N-acetylglucosamine transferase (ogt) was significantly higher in the haemocytes of shrimp fed
chitosan and
chitin than the control, but ogt was only significantly higher in the hepatopancreas of shrimp fed
chitosan. Dietary
chitin and
chitosan also showed positive effects on the transcription of peritrophin-like
protein. These findings suggest that both
chitin and
chitosan from D. similis are efficacious at boosting the immunity of shrimp by preventing and controlling
infectious diseases caused by Vibrio and have great potential to be used as a feasible
immunostimulant that significantly contributes to the circular economy.