ABSTRACT
A 56-day feeding trial was done to investigate the interactive effects of cholesterol (CHO) and phospholipids (PL) on the growth performance, immune response, expression of immune-related genes, and resistance against Vibrio alginolyticus of freshwater cultured white shrimp (Litopenaeus vannamei). A 3 × 3 experimental design was conducted with nine experimental diets containing three levels of CHO (0, 0.2%, and 0.4%) and three levels of PL (0, 2%, and 4%). The results indicated that the growth performance significantly (P < 0.05) increased with the increase in dietary CHO levels. Interactive effects between dietary CHO and PL on the growth parameters were not observed. Superoxide dismutase (SOD) and lysozyme activities were also significantly affected by dietary CHO levels. Furthermore, the interaction between these two additives was only detected in SOD activity. Shrimp fed experimental diet with CHO and PL supplementation showed better tolerance against Vibrio alginolyticus compared to the control, interactive effects (P < 0.05) were also detected on these two factors. The expression of immune deficiency (IMD) and lysozyme mRNA was up-regulated in shrimp fed diets with CHO and PL. The expression level of Toll-like receptor mRNA directly reflected the dietary CHO levels, which was not affected by dietary PL. The interaction between dietary CHO and PL was shown as the significant factor (P < 0.05) both in the expression of IMD and lysozyme mRNA, which indicated that different dietary levels of CHO and PL could strongly affect expression levels of some immune-relevant genes of the juvenile freshwater cultured L. vannamei.