Significant improvement of intestinal microbiota of gibel carp (Carassius auratus gibelio) after traditional Chinese medicine feeding

AimsIncreasing attention has been attracted to intestinal microbiota, due to interactions with nutrition, metabolism and immune defence of the host. Traditional Chinese medicine (TCM) feed additives have been applied in aquaculture to improve fish health, but the interaction with fish gut microbiota is still poorly understood. This study aimed to explore the effect of adding TCM in feed on the intestinal microbiota of gibel carp (Carassius auratus gibelio). Methods and ResultsBacterial communities of 16 fish intestinal contents and one water sample were characterized by high-throughput sequencing and analysis of the V4-V5 region of the 16S rRNA gene. The results showed that the composition and structure of the bacterial community were significantly altered by the TCM feeding. Some phyla increased markedly (Proteobacteria, Actinobacteria, Acidobacteria, etc.), while Fusobacteria were significantly reduced. Concurrently, the richness and diversity of the taxonomic units increased, and the microbiota composition of TCM-treated fish was more homogeneous among individuals. At the genus level, the addition of TCM tended to reduce the incidence of potential pathogens (Aeromonas, Acinetobacter and Shewanella), while stimulating the emergence of some potential probiotics (Lactobacillus, Lactococcus, Bacillus and Pseudomonas). ConclusionsThese data suggested that the feed additive could regulate the fish intestinal microbiota by reinforcing the microbial balance. Significance and Impact of the StudyThis study may provide useful information for further application of TCM for diseases prevention and stress management in aquaculture.</p

High levels of vegetable oils in plant protein-rich diets fed to gilthead sea bream (Sparus aurata L.): growth performance, muscle fatty acid profiles and histological alterations of target tissues

The feasibility of fish oil (FO) replacement by vegetable oils (VO) was investigated in gilthead sea bream (Sparus aurata L.) in a growth trial conducted for the duration of 8 months. Four isolipidic and isoproteic diets rich in plant proteins were supplemented with l-lysine (0&uacute;55 %) and soya lecithin (1 %). Added oil was either FO (control) or a blend of VO, replacing 33 % (33VO diet), 66 % (66VO diet) and 100 % (VO diet) of FO. No detrimental effects on growth performance were found with the partial FO replacement, but feed intake and growth rates were reduced by about 10 % in fish fed the VO diet. The replacement strategy did not damage the intestinal epithelium, and massive accumulation of lipid droplets was not found within enterocytes. All fish showed fatty livers, but signs of lipoid liver disease were only found in fish fed the VO diet. Muscle fatty acid profiles of total lipids reflected the diet composition with a selective incorporation of unsaturated fatty acids in polar lipids. The robustness of the phospholipid fatty acid profile when essential fatty acid requirements were theoretically covered by the diet was evidenced by multivariate principal components analysis in fish fed control, 33VO and 66VO diets

Managing the microbial community of marine fish larvae: a holistic perspective for larviculture

The availability of high-quality juveniles is a bottleneck in the farming of many marine fish species. Detrimental larvae-microbe interactions are a main reason for poor viability and quality in larval rearing. In this review, we explore the microbial community of fish larvae from an ecological and eco-physiological perspective, with the aim to develop the knowledge basis for microbial management. The larvae are exposed to a huge number of microbes from external and internal sources in intensive aquaculture, but their relative importance depend on the rearing technology used (especially flow-through vs. recirculating systems) and the retention time of the water in the fish tanks. Generally, focus has been on microbes entering the system, but microbes from growth within the system is normally a substantial part of the microbes encountered by larvae. Culture independent methods have revealed an unexpected high richness of bacterial species associated with larvae, with 100–250 operational taxonomic units associated with one individual. The microbiota of larvae changes rapidly until metamorphosis, most likely due to changes in the selection pressure in the digestive tract caused by changes in host-microbe and microbe-microbe interactions. Even though the microbiota of larvae is distinctly different from the microbiota of the water and the live food, the microbiota of the water strongly affects the microbiota of the larvae. We are in the early phase of understanding larvae-microbe interactions in vivo, but some studies with other animals than fish emphasize that we so far have underestimated the complexity of these interactions. We present examples demonstrating the diversity of these interactions. A large variety of microbial management methods exist, focusing on non-selective reduction of microbes, selective enhancement of microbes, and on improvement of the resistance of larvae against microbes. However, relatively few methods have been studied extensively. We believe that there is a lot to gain by increasing the diversity of approaches for microbial management. As many microbial management methods are perturbations of the microbial community, we argue that ecological theory is needed to foresee and test for longer term consequences in microbe-microbe and microbe-larvae interactions. We finally make some recommendations for future research and development

Probiotic supplementation influences the diversity of the intestinal microbiota during early stages of farmed Senegalese sole (Solea senegalensis, Kaup, 1858)

Ingestion of bacteria at early stages results in establishment of a primary intestinal microbiota which likely undergoes several stages along fish life. The role of this intestinal microbiota regulating body functions is crucial for larval development. Probiotics have been proved to modulate this microbiota and exert antagonistic effects against fish pathogens. In the present study, we aimed to determine bacterial diversity along different developmental stages of farmed Senegalese sole (Solea senegalensis) after feeding probiotic (Shewanella putrefaciens Pdp11) supplemented diet for a short period (10–30 days after hatching, DAH). Intestinal lumen contents of sole larvae fed control and probiotic diets were collected at 23, 56, 87, and 119 DAH and DNA was amplified using 16S rDNA bacterial domain-specific primers. Amplicons obtained were separated by denaturing gradient gel electrophoresis (DGGE), cloned, and resulting sequences compared to sequences in GenBank. Results suggest that Shewanella putrefaciens Pdp11 induces a modulation of the dominant bacterial taxa of the intestinal microbiota from 23 DAH. DGGE patterns of larvae fed the probiotic diet showed a core of bands related to Lactobacillus helveticus, Pseudomonas acephalitica, Vibrio parahaemolyticus,and Shewanella genus, together with increased Vibri o genus presence. In addition, decreased number of clones related to Photobacterium damselae subsp piscicida at 23 and 56 DAH was observed in probiotic-fed larvae. A band corresponding to Shewanella putrefaciens Pdp11 was sequenced as predominant from 23 to 119 DAH samples, confirming the colonization by the probiotics. Microbiota modulation obtained via probiotics addition emerges as an effective tool to improve Solea senegalensis larviculture.En prens