Bui T. B. Hang, Sujita Balami, and Nguyen T. Phuong
College of Aquaculture and Fisheries, Can Tho University, Can Tho city, Viet Nam
ABSTRACT
A feeding trial was carried out to investigate the effect of a potential probiotic bacterial strain, Lactobacillus plantarum (LP) supplemented in diets on survival and immune response of larval striped catfish (Pangasianodon hypophthalmus). The feeding trial was 8 weeks long in which three treatments were supplemented with 106, 107, and 108 CFU LP/g of feed and one control group without probiotic supplementation. The growth parameters were evaluated at the end of the feeding trial. In terms of immunity, fish blood was sampled for hematological parameters and lysozyme activity. After the feeding trial, the fish were challenged with Edwardsiella ictaluri for evaluating the bacterial resistance. Fish supplemented with L. plantarum diets showed significantly higher growth compared to those supplemented with the control diets. The weight gain, daily weight gain, and specific growth rate of treatment supplemented with 107 CFU LP/g were the highest. However, survival rates were not significantly different between the treatments. Results showed that hematological parameters (total white blood cells, monocytes, lymphocytes, neutrophils, and thrombocytes were significantly higher (p < 0.05) in the probiotic supplemented groups compared to those of the control group whereas total red blood cells were not significantly different between the treatments. Total lysozyme activity was significantly higher in the probiotic supplemented groups compared to those of the control group (p < 0.05) indicating higher immunity in the probiotic supplemented group. Accumulated mortalities after bacterial challenge were 0, 33.33, 20, 23.33, and 23.33 % for the negative control, positive control, 106, 107, and 108 CFU LP/g respectively. The results suggest that L. plantarum has a great potential for improving the survival of the striped catfish larvae as well as modulating the immune response. Hence, further research should be conducted to find the effect of Lactobacillus plantarum in different stages of striped catfish.