Effect of Potential Probiotic Lactococcus lactis Subsp lactis on Growth Performance, Intestinal Microbiota, Digestive Enzyme Activities, and Disease Resistance of Litopenaeus vannamei

The aims of this study were to evaluate the effects of Lactococcus lactis subsp. lactis on the growth, intestinal microbiota, digestive enzyme activity, and disease resistance of Litopenaeus vannamei. Diets containing four different concentrations of L. lactis (0 [basal diet], 106, 107, and 108 CFU g(-1)) were fed to white shrimps L. vannamei (average weight 5.89 +/- 0.36 g) for 8 weeks. At the end of the feeding trial, shrimps were immersed in Caspian Seawater (10.8 ppt) contaminated with 106 CFU ml(-1) pathogenic V. anguillarum for 2 h. Results revealed that growth rate, survival, and body protein level were increased with dietary supplementation of L. lactis. The activities of digestive enzymes (cellulose, lipase, amylase, and protease) were significantly higher in the groups fed with diets containing 10(7) or 10(8) CFU g(-1) L. lactis than those in the control. The Lactobacillus nd Bacillus counts were higher (P < 0.05) in the intestine of shrimps fed with L. lactis-supplemented diets. In addition, higher level of L. lactis supplementation decreased the Vibrio counts. Moreover, L. vannamei fed diet supplemented with 108 CFU g(-1) of L. lactis exhibited significantly the highest hematocyte count and post-challenge survival rate (79.2 %). Collectively, these results suggest that dietary supplementation of L. lactis subsp. lactis at 108 CFU g(-1) can promote growth performance, digestive enzyme activity, and disease resistance of L. vannamei