Abstract:Litopenaeus vannamei at (4.83±0.36)g body weight were fed with 0.1% heat-killed, 1% heat killed and 0.1% living Photobacterium damselae for 21 days respectively. The serum was collected at 0, 5, 10, 15 and 20 days post immunization and Phenoloxidase (PO), acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD) and lysozyme activity (UL) in the serum of L. vannamei were determined to evaluate the non-specific immune effect of P. damselae After 21 days, the shrimps were challenged by white spot syndrome virus (WSSV) and the mortalities of challenging test were recorded. The results showed that most PO, ACP, AKP, UL and SOD in the serum of L. vannamei of the test groups were significantly different (P<0.05 or P<0.01), and the resistance ability of shrimps to WSSV was also significantly enhanced by the diet supplemented with P. damselae The group fed with 10g heat-killed P. damselae per 1 kg shrimps exhibited the strongest resistance to WSSV in 14 days and its final cumulative mortality was 63.3%±5.8%, while the control was 96.7%±7.3%. The results indicated that P. damselae improved shrimp non-specific immunity and its resistance to WSSV, suggesting that it might be a promising diet supplement in shrimp farming.
