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The main challenge in shrimp farming is the high prevalence of diseases caused by pathogenic bacteria from the Vibrionaceae family. Natural extracts enriched with prebiotic and antibacterial compounds have been proposed as alternatives to the controversial use of antibiotics. In this study, a flavonoid-enriched extract (11.54 ± 1.81 mg QE/g DW) obtained from Agave lechuguilla bagasse was evaluated as a feed supplement at 0.0, 0.1, 0.3, and 0.6% in the diet for the Pacific white shrimp (Penaeus vannamei), before and after infection with Vibrio parahaemolyticus strain CIBGEN-003. The effect of the lechuguilla extract on the gut microbiome and vibriosis prevalence was assessed through high-throughput sequencing of 16S rRNA genes analysis, comparing the bacterial community at 0 h, 48 h, and 72 h of the challenge with the pathogenic strain. A global shift in the relative abundance was observed at phylum and class level and among the dietary treatments during the infection. In particular, an increase in the abundance of Vibrionaceae was observed. A higher survival of the shrimp fed with the lechuguilla extract was observed compared to control, and a lower vibriosis prevalence with the two highest inclusion levels, 0.3 and 0.6%. These findings were related to the differences in the microbial community, according to the inclusion level of the lechuguilla extract before the inoculation of V. parahaemolyticus. Results provide a new perspective to further understand the required structure of the gut microbiome to prevent diseases in shrimp farming. Modulation of the gut microbial community by the flavonoids, quantified in the lechuguilla extract, significantly increased the resistance of P. vanamei against V. parahaemolyticus, supporting the use of plant extracts as alternatives to traditional disease-fighting aquaculture practices. • The flavonoid-enriched extract, used in this study, contain flavonoids known as a promoters of microbial diversity and anti-inflamatory effects. • This is the first time that a flavonoid-enriched extract from Lechuguilla is applied as fed supplement for shrimp. • The shrimps fed with the diets included with the Lechuguilla extract presented a diferent microbial structure than the control. • The addition of 0.3% and 0.6% of the Lechuguilla extract as fed additive gave resistance to the animals against vibriosis. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of rice bran fermented with a consortium of Bacillus and Lysinibacillus strains (RB + BLb) on the bacterial community structure and composition in the gastrointestinal tract of Pacific white shrimp (Penaeus vannamei), as well as its effect on growth performance and health status. Rice bran fermented with a commercial probiotic (RB + Com) was also evaluated for comparative purposes. Rice bran with or without probiotics, pre-fermented for 24 h, was directly added to the rearing water of juvenile shrimp for 4 weeks. At the end of the experimental period, shrimp treated with RB + BLb had a slightly better shrimp growth performance and survival than the control group; however, the differences were not statistically significant (p > 0.05) among treatments. Moreover, histological analyses showed that shrimp treated with RB + BLb improved the nutritional status compared to other treatments, by inducing an increase in lipid reserves of hepatopancreas epithelial cells. The analysis of the bacterial community composition revealed that the most prevalent families were Rhodobacteraceae , Vibrionaceae and Flavobacteriaceae. Although sequences affiliated to the Rhodobacteraceae family were more abundant in shrimp treated RB + Com, a lower proportion of sequences affiliated to the Vibrionaceae family was found in shrimp treated with unfermented rice bran (RB) or RB + Com, when compared with the control group or those treated with RB + BLb. The abundance of sequences affiliated to the Flavobacteriaceae family was significantly lower in shrimp treated with RB + BLb or RB + Com than the control group or those treated with RB. These results could explain, in part, the mechanisms of action whereby the use of rice bran fermented with a consortium of probiotic bacteria confer beneficial effects on shrimp culture. Unlabelled Image • Rice bran fermented with a consortium of Bacillus and Lysinibacillus strains showed great potential as safe probiotics. • Fermented rice bran modified the bacterial communities in the hepatopancreas of shrimp. • Fermented rice bran offered a slightly better growth performance and survival than the control group. [ABSTRACT FROM AUTHOR]