Immune responses and resistance against Vibrio parahaemolyticus induced by probiotic bacterium Arthrobacter XE-7 in Pacific white shrimp, Litopenaeus vannamei

A 63-d feeding experiment was conducted to determine the effects of dietary supplementation of probiotic bacterium Arthrobacter XE-7 on immune responses and resistance against Vibrio parahaemolyticus in the Pacific white shrimp, Litopenaeus vannamei. The probiotic bacteria were administered orally at four different doses of 0, 10(6), 10(8), and 10(10) colony-forming unit (CFU)/g feed for shrimp. On Day 50, the shrimp were challenged with Vibrio parahaemolyticus by bath. On Days 7, 21, 49, and 63, six shrimp per tank were sampled to take intestine and hemolymph. With increasing dietary supplementation of probiotic bacteria, shrimp mortality decreased from 63.16% (the control) to 55.9% (10(6) CFU/g feed), 51.75% (10(8) CFU/g feed), and 51.78% (10(10) CFU/g feed), respectively. Vibrio counts in intestine of shrimp fed probiotic bacterium Arthrobacter XE-7 was generally lower than that in the control shrimp (P < 0.05). The probiotic bacteria generally increased the immune parameters in shrimp, that is, total hemocyte counts, percentage phagocytosis, respiratory burst activity, and serum phenoloxidase activity. The results showed that probiotic bacterium Arthrobacter XE-7 can be used as probiotic in shrimp feed.