Effects of Dietary Administration of Probiotic Halomonas sp. B12 on the Intestinal Microflora, Immunological Parameters, and Midgut Histological Structure of Shrimp, Fenneropenaeus chinensis

The experiment was conducted to investigate the effects of oral administration of probiotic Halomonas sp. B12 (previously isolated from the intestine of Fenneropenaeus chinensis) on the intestinal microflora, immunological parameters, and midgut histological structure of F. chinensis. Shrimp (initial weight: 4.00 ± 0.10 g) were fed diets containing Halomonas sp. B12 at 0 (control), 3.68 × 107 (T1), and 7.18 × 1010 (T2) colony-forming units per gram for 6 wk, respectively. The results showed that the total bacterial counts significantly increased (P   0.05). PO activity in plasma was higher in T2 than that in T1. Cumulative shrimp mortality after 10-d white spot syndrome virus (WSSV) challenge test significantly decreased with increasing dietary probiotic B12 (P   0.05). The oral administration of probiotic B12 to F. chinensis was beneficial to protect the integrity of shrimp intestinal mucosal layer. In summary, even though the low dose (T1) had some effects on bacterial counts and immunological parameters, only the high dose (T2) significantly increased the resistance of the shrimp to WSSV.