Abstract
The aim of this study was to stu/sdy the effect of astaxanthin (AX) on growth, physiological, antioxidant and immune response on Whiteleg Litopenaeus vannamei.
The current study was conducted at a private marine shrimp farm at Borg-El Arab, Alexandria Province, Egypt. White leg shrimp (L. vannamei) were obtained from a shrimp hatchery and larviculture, transported to the farm, and left for acclimation in indoor 1-m3 fiberglass tanks for two weeks. Then shrimp juveniles postlarvae-20 (PL-20) of Pacific white shrimp was obtained from a hatchery in Domeitta Province, Egypt. After 3 days of acclimation, shrimps (PL-23) (0.340 ± 0.041 g) were randomly distributed into 24 × 500-L fiberglass tanks (four replicate tanks per treatment). Experimental treatments were control (0.0): Commercial feed only, Treatment 1: Commercial feed containing AX (50 mg/kg feed), Treatment 2: Commercial feed containing AX (100 mg/kg feed), Treatment 3: Commercial feed containing AX (200 mg/kg feed), Treatment 4: Commercial feed containing AX (400 mg/kg feed), Treatment 5: Commercial feed containing AX (800 mg/kg feed). The results showed that, the addition of astaxanthin in feed of L. vannamei improved the antibacterial activity, water quality, digestive enzyme activity, immune response parameters, antioxidant activity, antioxidant gene expression, relative level of protection after Bacterial with improvement of intestinal morphometric analysis.This study concluded that, the astaxanthin must be added in feed of L. vannamei to improve the productivity and shrimp immunity and reduction of diseases incidences.

Key words: Astaxanthin - Growth – Physiological – Antioxidant - Immune response - Whiteleg Litopenaeus vannamei