Dietary supplementation with plant essential oils-loaded chitosan nanoparticles improves growth, body composition, digestive enzymes, and immune response in whiteleg shrimp (Litopenaeus vannamei): Influence on histopathology and survivability against Vibrioparahaemolyticus.

The impacts of dietary chitosan nanoparticles loaded with pumpkin seed oil (ChNPs/PSO) and\or Flaxseed oil (ChNPs/FSO) on growth performance, immune responses, and resistance of whiteleg shrimp, Litopenaeus vannamei, against Vibrio parahaemolyticus were investigated. Four experimental diets: 1 g/kg chitosan nanoparticles (ChNPs) as a control diet, 2 mL/kg (ChNPs/PSO), 2 mL/kg (ChNPs/FSO), and a mixture of ChNPs/PSO + ChNPs/FSO at an equal concentration (2:2 mL/kg) were prepared to feed L. vannamei for 56 days. After the feeding trial, the shrimp were challenged via immersion with Vibrio parahaemolyticus (1 × 107 CFU mL-1) for 48 h. Results showed that growth performance parameters like final weight, weight gain, specific growth rate (SGR), feed intake, feed conversion ratio (FCR), and average daily growth (ADG)) significantly increased in all supplemented groups (P < 0.05) compared to the chitosan nanoparticles control group. In addition, the survival rate and shrimp biomass showed the same trend as the growth performance, especially with ChNPs/PSO and ChNPs/PSO + ChNPs/FSO (P < 0.05). Body composition analysis revealed significant differences (P < 0.05) in crude protein and crude lipid in all supplemented groups compared to the control diet. The immunological responses, such as total hemocyte count, lysozyme activity, bactericidal activity, and phagocytic index, were significantly improved (P < 0.05) in all supplemented groups. Moreover, superoxide dismutase (SOD) enzyme activity, phagocytic and phenoloxidase activities were significantly higher in the treatment groups fed ChNPs/PSO and ChNPs/PSO + ChNPs/FSO than in other groups. Immuno-related gene expressions of prophenoloxidase (LvproPO) and hemocyanin (LvHc) displayed significant up-regulation in all treated groups compared to the group fed ChNPs only. Following V. parahaemolyticus challenge, notable amelioration was observed in the tissues' architecture, correlated with boosting the L. vannamei resistance in shrimp-fed PSO and FSO-loaded ChNPs. Additionally, the cumulative mortality rate of shrimp in all experimental feeds was significantly reduced compared to the control group. Considerably, dietary ChNPs/PSO and/or ChNPs/FSO at a concentration of 2 mL/kg diet noticeably improve growth, immune status, and antioxidative response, leading to V. parahaemolyticus resistance in cultured shrimp.