Effects of lactic acid bacteria and the corresponding supernatant on the survival, growth performance, immune response and disease resistance of Litopenaeus vannamei

Fifty-three lactic acid bacteria (LAB) strains were respectively isolated from commercial probiotics, and the intestinal tracts of shrimp (Fenneropenaeus chinensis) and fish (Acanthogobius hasta). The antibacterial and adhesive activities of these strains were examined, the results showed that Lactobacillus pentosus HC-2 (L. pentosus HC-2) and Enterococcus faecium NRW-2 (E. faecium NRW-2) had higher antibacterial and adhesive activity, respectively, the identification of strains was based on the 16S rRNA analysis. The aim of this study was to investigate and compare the effects of E. faecium NRW-2, L. pentosus HC-2 and the corresponding supernatant on the immune response and growth performance of shrimp (Litopenaeus vannamei). Real-time PCR was used to determine the expression levels of immune- and digestion-related genes in the midgut and hepatopancreas. Our results suggested that E. faecium NRW-2 had higher stimulation to all tested genes, except crustin and proPO in the midgut at two weeks and four weeks post-feeding, respectively, while L. pentosus HC-2 and its corresponding supernatant had higher induction of genes in the hepatopancreas. According to the challenge tests, all of the treatment groups had significantly higher survival rate than the control group. Moreover, the specific growth rates of shrimp fed with selected strains were higher than the control group; whereas that of the supernatant of the L. pentosus HC-2-containing group was lower than the control even though it was not significant. The present study indicates that the selected strains could be used as effective components in the shrimp diet and were better than the supernatant of L. pentosus HC-2. Statement of relevance: The present study indicates that E. faecium NRW-2 and L. pentosus HC-2 could be used as effective components in the shrimp diet and were better than the supernatant of L. pentosus HC-2. This study provided a scientific basis for the development of product safety input and the popularization and application of lactic acid bacteria in aquaculture. (C) 2015 Elsevier B.V. All rights reserved.