Effects of supplemental Azomite in diets on growth, immune function and disease resistance of white shrimp (Litopenaeus vannamei)

This study was conducted to evaluate effects of dietary Azomite, a natural mineral of volcanic ash, on growth performance, digestive enzyme activities, serum non-specific immunity and disease resistance of white shrimp (Litopenaeus vannamei). Graded levels of 0.0 g kg^-1 (control group), 2.0, 4.0, 6.0 and 8.0 g kg^-1 Azomite were supplemented in basal diet to feed shrimps. After 6 weeks feeding, weight gains of the 2.0 and 4.0 g kg^-1 Azomite groups were significantly higher than that of the control group (P < 0.05). Compared with control group, the activities of stomach protease, hepatopancreas lipase, and serum alkaline phosphatase, lysozyme and phenoloxidase were significantly increased by the 4.0 g kg^-1 Azomite addition (P < 0.05). When subjected to hypoxia stress, the lethal times of the first shrimp and all shrimps were both delayed by the addition of 2.0-6.0 g kg^-1 Azomite to diets, compared with the lethal time of control group. At the 96th hour after the injection of bacterium (Vibrio alginolyticus), the accumulated mortality of 4.0 g kg^-1 Azomite addition group was 34.6% lower than that of control group (P < 0.05). The results showed that dietary levels of 2.0 and 4.0 g kg^-1 Azomite can improve the growth performance, digestive enzyme activities, serum non-specific immune function and disease resistance of white shrimp.