Probiotics are frequently used in intensive shrimp farming to help secure or enhance health and performance . This study assessed the effects of in-feed supplementation with a Bacillus -based probiotic on shrimp performance, composition and inferred functionality of the digestive microbiota with the view to screen , if any, the microbial pathways manipulated.
The 8 -week (56 days) grow-out trial used whiteleg shrimp ( 1.2 g) in clear water tanks (290L tanks; 20 ppt; 27°C) fed to apparent satiation . Two treatments were applied in quadruplicate: a control group (CON ) fed a non-supplemented diet (BioMAR) and a probiotic group (BAC ) fed the same basal feed supplemented with proprietary strains of Bacillus pumilus and Bacillus subtilis at 6×106 CFU/Kg feed (50:50 by CFU ; Lallemand, France). Microbiota composition (16S rRNA V3-V4 region ) and functional inference (PICRUSt2 ) were analyzed in the digestive gland (HP) and rearing water at the start and end of the trial.
D ietary treatments had a significant impact on the HP bacterial composition . At the end of the trial, the probiotic group showed a lower prevalence of Vibrionales and a higher prevalence of Bacillus genus as well as of members of the Roseobacter clade (Phaeobacter , Ruegeria and Paracoccus) in particular . S hannon diversity was also significantly higher in the BAC group and this index was significantly correlated with the Rhodobacteraceae/Vibrionales (R/V) ratio (r = 0.76) (Rodiles et al., 2022). Functional inference of the HP microbiota revealed 645 KO differently abundant between groups . Of these, 96% were higher in the BAC compared to the CON group and corresponded to the enhancement of 15 KEGG pathways involved in vitamins and cofactors production, bile acid production, denitrification, fermentation and of serum resistance to pathogens. Some effects on the water microbiota were documented and will be presented.
In conclusion, the probiotic-feed group exhibited a digestive microbiota with enhanced taxonomic and functional diversity. This diversity was associated with specific nutritional and health advantages, as inferred from their functional characteristics. The primary factor contributing to this diversity appears to be a decrease in the prevalence of the Vibrionales taxon due to probiotic feeding. Given that Vibrionales possess limited functional attributes, their reduced prevalence fosters a more diverse and functional microbiota offering both nutritional and health benefits.
Rodiles et al . Relationship between alpha diversity and Rhodobacteraceae/Vibrionales ratio as a potential biomarker of the intestinal microbiota of whiteleg shrimp Litopenaeus vannamei . World Aquaculture May 24 - 27, 2022, Merida (Mexico).