The growth performance, body composition and nonspecific immunity of white shrimps (Litopenaeus vannamei) affected by dietary Astragalus membranaceus polysaccharide.

The aim of this study was to investigate the effects of Astragalus membranaceus polysaccharide (AMP) on the growth performance, body composition and non-specific immune index of white shrimps (Litopenaeus vannamei). AMP was used to replace 0 (control), 10, 30, and 50 g kg of the cellulose in the basic diet to formulate four kinds of test feeds. Sixplicate groups of shrimps with an average weight of 0.51 ± 0.03 g were fed with one of diets four times daily. Dietary 50 and 30 g kg of AMP increased body weight gain, feed efficiency, body protein, superoxide dismutase activity, catalase activity, acid phosphatase activity, lysozyme, disease resistance ability against Vibrio alginolyticus and decreased body lipid level of shrimps compared with those of the control group. However, a high level of AMP (50 g kg) did not improve the efficiency of AMP on the growth performance, body composition and non-specific immune index of shrimps further compared to moderate level of AMP (30 g kg). The results demonstrated that AMP with appropriate dose could promote the growth of shrimps and improve their disease resistance.