Effect of Sargassum polycystum Enrichment in Feed on Immune Response and Survival Rate of Litopenaeus vannamei Against Vibrio harveyi Infection.

Prior studies on Sargasum sp. as an immunostimulant were mostly focused on injection and immersion methods. Moreover, large-scale aquaculture requires practical applications to minimize stress caused by handling. The objective of this research was to investigate the effect of feed enrichment with extract of Sargassum polycystum on the immune response and survival rate of Litopenaeus vannamei. This study used S. polycystum which is a brown seaweed that contains bioactive compounds such as flavonoids and phenolics, was added to shrimp feed at varying concentrations (5, 10, and 15 g/kg). Immune parameters, including Total Hemocyte Count (THC), Differential Hemocyte Count (DHC), and immune gene expression (lectin and proPO) were analysed before and after the challenge test using Vibrio harveyi. The results showed that S. polycystum extract significantly increased THC, DHC, and immune gene expression compared to the control group, indicating an increase in immune defense. However, the enrichment did not significantly affect on shrimp growth. Post challenge test, the highest survival rate (80.56%) obtained in shrimp were fed with 10 g/kg S. polycystum extract. The results showed that dietary supplementation with extract of S. polycystum enhanced the immune system of L. vannamei and providing a preventive approach against pathogen infection.