Regresar

Probiotic effect of Streptomyces strains alone or in combination with Bacillus and Lactobacillus in juveniles of the white shrimp Litopenaeus vannamei

Abstract:

We studied the effect of two Streptomyces strains, alone and combined with Bacillus and Lactobacillus, on the growth, microflora, hemocyte count, and superoxide dismutase (SOD) activity of the shrimp Litopenaeus vannamei. Eight experimental groups were fed for 30 days either with N7 (Streptomyces N7), RL8 (Streptomyces RL8), Strep (Streptomyces N7 and RL8), Lac (Lactobacillus graminis), Bac (a Bacillus mixture), or a combination of Lac-Strep, Bac-Strep, and Mix (a mixture of Bac, Lac, and Strep). A non-probiotic fed group served as the control. After treatment, shrimps were challenged with Vibrio parahaemolyticus and survival was recorded for 4 days. The Bac-Strep group showed significantly better (P < 0.05) growth performance than the control group, followed by good but not significant performance of groups N7, RL8, and Strep. All Streptomyces-containing groups, except Mix, showed a significant reduction of Vibrio from hepatopancreas, the same as Bac-Strep from water, whereas they produced a mild reduction of heterotrophs. All probiotic-fed groups had a higher hemocyte count than the control, but it was only significant for Strep and Bac-Strep. Challenging shrimps with V. parahaemolyticus stimulated the SOD activity of probiotic-fed groups, except for RL8, with higher but not significant SOD, and the groups N7 and Strep. All probiotic-fed groups showed a significantly higher survival rate than the control group, except for N7 and Strep. This study revealed that some Streptomyces strains alone or combined with other genera, primarily Bacillus, exert a probiotic effect on shrimps by improving growth parameters, regulating immune response, modulating host and water microbiota, and increasing resistance to disease.