Inhibition ability of probiotic, Lactococcus lactis, against A. hydrophila and study of its immunostimulatory effect in tilapia (Oreochromis niloticus)

Abstract

The present study was designed to investigate the inhibition ability of probiotic, Lactococcus lactis RQ516, against A. hydrophila in vitro and its immunostimulatory effect in tilapia, Oreochromis niloticus as growth promoter. Six tanks were used (T-1 and control treated with and without RQ516, respectively) and three replicates per treatment. The inhibition ability assay in vitro showed that the minimum diameter of the inhibition zone (P < 0.05) was 7.43 ± 0.47 mm at 6 h and the final diameter at 24 h was 14.77 ± 1.17 mm. After 40 days, probiotic treatment as water additives significantly improved the final weight and daily weight gain (DWG) (P < 0.05). A significant increase (P < 0.05) in the total protein and globulin concentration of tilapia blood serum could be found in T-1 compared with the control. These immune responses were generally more pronounced with probiotic-treated tilapia. As for immune responses, the higher respiratory burst activity (RBA), lysozyme content (LC), myeloperoxidase (MPO) and superoxide dismutase (SOD) activities were observed in T-1 (P < 0.05) than the control. It indicated that probiotic Lactococcus lactis RQ516 was beneficial for tilapia in terms of increasing final weight, DWG and the concentrations of serum protein and globulin and enhancing immune responses.

International Journal of Engineering, Science and Technology, Vol. 2, No. 7, 2010, pp. 73-80