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The protective effects of a phage cocktail composed of vB_Vc_SrVc2 and vB_Vc_SrVc9 were tested in Pacific white shrimp (Litopenaeus vannamei) postlarvae, which were originally isolated from diseased shrimps and selected due to their broad-host-range properties against several pathogenic Vibsrio species. We used culture-dependent and culture-independent approaches to explore its effect on bacterial communities associated with shrimp postlarvae. Both methods revealed that the levels of Vibrio species were significantly reduced after phage cocktail administration. Phage-treated shrimp also exhibisuppted lesser damage and higher lipid accumulation in B cells of the hepatopancreas, as revealed by histopathological examination. Taken together, this study provides clear evidence that phage therapy can selectively and effectively reduce Vibrio species, thereby providing an environmentally safe alternative to the prophylactic use of antibiotics in shrimp aquaculture. [ABSTRACT FROM AUTHOR]

The present study evaluated the effect of temporal periods of hypothermia and hyperthermia, followed by an optimal temperature recovery phase on the growth, survival, and physiological response of Penaeus vannamei. Post-larvae were exposed to stress periods for 7 and 14 days at 22 °C and 32 °C each, followed by a recovery phase at 28 °C to complete seven experimental weeks, and were compared with a control group maintained at 28 °C. Weight gain, specific growth rate, feed intake, feed conversion ratio, and survival were weekly determined. Muscle, hepatopancreas, and hemolymph were sampled on the 14th day of the recovery phase for biochemical composition, and antioxidant and digestive enzyme activities determination. The shrimp presented a higher growth rate during short-term hyperthermia in contrast to shrimp under hypothermia that presented compensatory growth after thermal stress when the temperature was restored at 28 °C. Hyperthermia increased 12–13% the feed intake while this was diminished 21–29% by the hypothermia periods. Shrimp undergo metabolic adjustments following thermal stress, with short hypothermia increasing the lipase activity and lipid storage in the hepatopancreas, while short hyperthermia also enhances chymotrypsin activity and leads to higher protein and lipid accumulation. Conversely, prolonged hyperthermia induces greater energy consumption, depleting lipid and glycogen stores, while hypothermia causes scarce mobilization of energy reserves during recovery phase. Antioxidant enzyme activities were not affected by short-thermal stress (7d), while prolonged thermal stress (14d) significantly affected SOD, CAT, and GPx activities. The present study provides important insights into the physiological plasticity of P. vannamei during recovery from thermal stress. [Display omitted] • Shrimp P. vannamei has physiological plasticity during recovery from thermal stress. • The 7-day hypothermia increases lipase activity and lipid storage in P. vannamei. • Prolonged hyperthermia reduces lipids and glycogen stores in Penaeus vannamei. • Prolonged thermal stress affects SOD, CAT, and GPx activities in Penaeus vannamei. [ABSTRACT FROM AUTHOR]

The aims of this study were to explore the effect of a probiotic consortium at different concentrations (low, medium and high) on bacterial community structure and composition in the hepatopancreas and digestive tract of Pacific white shrimp Litopenaeus vannamei reared under superintensive conditions, as well as to investigate its effect on gene expression of antioxidant enzymes. After the 69-day experimental period, shrimp treated with high probiotic concentration showed higher final growth, specific growth rate, weight gain and survival (p <.05) than those treated with low probiotic concentration or without probiotics; however, there were no significant differences compared to those treated with medium probiotic concentration. The analysis of the bacterial community structure revealed significant differences among treatments with and without probiotics; however, there were no differences between hepatopancreas and digestive tract samples, independently of the treatment received. Moreover, there were no differences in those samples from shrimp treated with probiotics at medium and high concentrations. The analysis of the bacterial community composition showed a higher proportion of Alphaproteobacteria (particularly members belonging to the family Rhodobacteraceae) in hepatopancreas and digestive tract samples from shrimp treated with probiotics at medium and high concentrations than in those treated with low probiotic concentration or without probiotics. In contrast, a higher proportion of Gammaproteobacteria (particularly members belonging to the families Alteromonadaceae , Moraxellaceae , Pseudomonadaceae and Vibrionaceae) was found in both sample types from shrimp treated without probiotics than in those treated with probiotics, independently of the concentration tested. At the end of the study, the levels of MnSOD (manganese superoxide dismutase) and CAT (catalase) transcripts were similar among hepatopancreas samples from shrimp treated with or without probiotics; however, the levels of GPx (glutathione peroxidase) transcripts drastically increased in those samples from shrimp treated without probiotics. These results could explain, in part, the mechanisms (i.e., competitive exclusion and immunomodulation) whereby probiotics confer beneficial effects to the host. • A probiotic consortium of Bacillus species and Enterococcus faecalis improved growth performance in Pacific white shrimp. • The probiotic consortium modified bacterial communities in the shrimp hepatopancreas and digestive tract. • Levels of glutathione peroxidase (GPx) transcripts only increased in shrimp treated without probiotic consortium. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus and Vibrio harveyi are commonly associated with brine shrimp, where they proliferate at the time of hatching and colonize nauplius surfaces, becoming a potential risk to organisms feeding on them. Among the strategies to prevent their occurrence, the use of chemotherapeutic agents and disinfectants could be considered; however, these strategies have side effects on the quality of brine shrimp and the environment. As a consequence, the use of bacteriophages (phages) is gaining interest in aquaculture. In this study, we investigated the effect of phage therapy (single phages and cocktails) on hatching and survival of brine shrimp ( Artemia franciscana ) cysts and nauplii exposed to pathogenic strains of V. parahaemolyticus and V. harveyi. The results revealed that application of single phages enhanced significantly ( p  < 0.05) the hatching success and survival rate, even at low multiplicity of infection (MOI). Subsequently, these promising phages were mixed (cocktails) and administered to brine shrimp cysts and nauplii exposed to both pathogenic Vibrio species. The results also revealed an enhanced hatching success (100% in both cases) and survival rate (from 85 to 89%) in groups treated with phage cocktails, whereas control groups had a hatching success of around 50% and survival rate from 40 to 50%. Given this, phage cocktails offer an alternative to chemotherapeutic agents routinely used in brine shrimp production. [ABSTRACT FROM AUTHOR]

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]