Dietary supplementation with triglyceride tributyrin (TBT), a butyrate precursor, has been associated with beneficial effects on fish health and improvements in the ability of carnivorous fish to ...tolerate higher levels of plant-based protein. In this study, we aimed to investigate the effects of a plant-based diet supplemented with TBT on the structural diversity and putative function of the digesta-associated bacterial communities of rainbow trout (Oncorhynchus mykiss). In addition to this, we also assessed the response of fish gut digestive enzyme activities and chyme metabolic profile in response to TBT supplementation. Our results indicated that TBT had no significant effects on the overall fish gut bacterial communities, digestive enzyme activities or metabolic profile when compared with non-supplemented controls. However, a more in-depth analysis into the most abundant taxa showed that diets at the highest TBT concentrations (0.2% and 0.4%) selectively inhibited members of the Enterobacterales order and reduced the relative abundance of a bacterial population related to Klebsiella pneumoniae, a potential fish pathogen. Furthermore, the predicted functional analysis of the bacterial communities indicated that increased levels of TBT were associated with depleted KEGG pathways related to pathogenesis. The specific effects of TBT on gut bacterial communities observed here are intriguing and encourage further studies to investigate the potential of this triglyceride to promote pathogen suppression in the fish gut environment, namely in the context of aquaculture.
Probiotic administration can be a nutritional strategy to improve the immune response and growth performance of fish. The current study aimed to evaluate the effects of a probiotic blend (Bacillus ...sp., Pediococcus sp., Enterococcus sp., Lactobacillus sp.) as a dietary supplement on growth performance, feed utilization, innate immune and oxidative stress responses and intestinal morphology in juvenile Nile tilapia (Oreochromis niloticus). The probiotic was incorporated into a basal diet at three concentrations: 0 g/kg (A0: control), 3 g/kg (A1: 1.0×106 colony forming unit (CFU)/g) and 6 g/kg (A2: 2.3×106 CFU/g diet). After 8 weeks of probiotic feeding, weight and specific growth rate where significantly higher in fish-fed A1 diet than in fish-fed A0. Alternative complement in plasma was significantly enhanced in fish-fed A2 when compared with A0. The hepatic antioxidant indicators were not affected by probiotic supplementation. Villi height and goblet cell counts increased significantly in the intestine of fish-fed A1 and A2 diets compared with A0. The dietary probiotic supplementation was maintained until 20 weeks of feeding. Then the selected immune parameters, digestive enzymes and apparent digestibility of diets were studied. No effect of probiotic feeding was observed after that longer period supplementation. The dietary supplementation of mixed species probiotic may constitute a valuable nutritional approach towards a sustainable tilapia aquaculture. The improvement of the immune responses and intestinal morphology play an important role in increasing growth performance, nutrient absorption and disease resistance in fish, important outcomes in such a competitive and developing aquaculture sector.
The effects of using plant ingredients in Senegalese sole (
Solea senegalensis
) diet on immune competence and intestine morphology and microbial ecology are still controversial. Probiotics or ...immunostimulants can potentially alter the intestinal microbiota in a way that protects fish against pathogens. The current study aimed to examine the intestine histology and microbiota and humoral innate immune response in juvenile sole fed diets with low (35 %) or high (72 %) content of plant protein (PP) ingredients supplemented with a multispecies probiotic bacteria or autolysed yeast. Fish fed the probiotic diet had lower growth performance. Lysozyme and complement activities were significantly higher in fish fed PP72 diets than in their counterparts fed PP35 diets after 17 and 38 days of feeding. At 2 days of feeding, fish fed unsupplemented PP72 showed larger intestine section area and longer villus than fish fed unsupplemented PP35. At 17 days of feeding, fish fed unsupplemented PP72 showed more goblet cells than the other dietary groups, except the group fed yeast supplemented PP35 diet. High dietary PP level, acutely stimulate fish innate immune defence of the fish after 2 and 17 days of feeding. However, this effect does not occur after 73 days of feeding, suggesting a habituation to dietary treatments and/or immunosuppression, with a reduction in the number of the goblet cells. Fish fed for 38 days with diets supplemented with autolysed yeast showed longer intestinal villus. The predominant bacteria found in sole intestine were
Vibrio
sp. and dietary probiotic supplementation caused a reduction in
Vibrio
content, regardless of the PP level.
In aquaculture, infectious diseases are the major cause of economic losses. Probiotic supplementation may change the microbiota of the digestive tract and modulate the immune defences and nutritional ...performance. This study was conducted to evaluate the dietary supplementation of multi-species (A: Bacillus sp., Pediococcus sp., Enterococcus sp., Lactobacillus sp.) and single-species probiotics (B: Pediococcus acidilactici) on growth performance and gut microbiota of rainbow trout (Oncorhynchus mykiss). A basal diet was supplemented with probiotic A or B, at two concentrations each (A1, A2, B1 and B2) or not supplemented (control treatment). Diets were distributed to 30 groups of 20 fish, 3 times a day. The gut microbiota was analysed at the end of the feeding trial (96days) with 16S rDNA denaturing gradient gel electrophoresis (16S-DGGE). Changes in gut microbial community were assessed by Shannon index (H´) and number of operational taxonomic units (OTUs). After 56days of feeding, weight gain was significantly improved in fish fed diet A1 when compared to the control group. Dietary probiotic supplementation changed the gut microbial composition. Number of OTUs (R) was higher in fish fed A1 (multi-species at lower concentration) than in control group, while H´ was higher in fish fed A1, B1 and B2.
•Tolerance limit (LD) of Aeromonas hydrophila for Arapaima gigas was determined.•For A. gigas, the LD50-96h was of 1.8×108CFU/mL.•The intradermal inoculation of 1.8×108CFU/mL A. hydrophila caused ...91.6% of mortality in fish and several clinical signs.•Fish had erratic movement, body abnormal coloration, hemorrhagic foci and abrasion of dorsal fin.•Fish had depigmentation in the tegument, body lesions, loss of balance, reduction of respiratory movements, hemorrhagic foci and necrotic hemorrhages.
Aeromonas hydrophila is causing substantial economic losses in world aquaculture. This study determined the tolerance limit (LD50-96h) of A. hydrophila in Arapaima gigas, and also investigated the clinical signs after intradermal inoculation. Arapaima gigas fingerlings were inoculated intraperitoneally with 0 (control), 1.0×105, 1.0×106, 1.0×107, 1.0×109 and 1.0×1010CFU/mL of A. hydrophila for the determination of LD50-96h, which was 1.8×108CFU/mL. In another trial with intradermal inoculation of 1.8×108CFU/mL A. hydrophila, there was a 91.6% of mortality between 8 and 23h, and several clinical signs were found. As follows: depigmentation in the tegument, lesions in the tail and fins, loss of balance, reduction of respiratory movements, hemorrhagic foci, necrotic hemorrhages in the kidney, liver and swim bladder, splenomegaly, ascites in the abdominal cavity and hyperemia, enlargement of the gall bladder, among other clinical signs observed. The results showed that A. gigas has a relative tolerance to A. hydrophila when compared to other Neotropical fish species.
The influence of two commercial probiotics on the growth, innate immune parameters and intestinal morphology of rainbow trout (Oncorhynchus mykiss) juveniles (initial weight: 16.4 ± 0.4 g) was ...evaluated. Two probiotic types: A, multi-species (Bacillus sp., Pedicoccus sp., Enterococcus sp., Lactobacillus sp.) and B, mono-species (Pediococcus acidilactici) were tested at two levels each (A1: 1.5 g kg−1, 8.6 × 105 CFU g−1; A2: 3 g kg−1, 1.6 × 106 CFU g−1; B1: 0.1 g kg−1, 2.6 × 104 CFU g−1; B2: 0.2 g kg−1, 7.2 × 104 CFU g−1) versus an unsupplemented diet (C). Diets were distributed to sextuplicate tanks, three times a day to visual satiation for 8 weeks. Growth performance and immune responses (plasma lysozyme, ACH50, peroxidase and head kidney respiratory burst) were determined at 4 and 8 weeks of feeding. Body composition and intestine morphology were determined at the end of the feeding trial.
At 8 weeks, the lower dose of multi-species probiotic (A1) improved growth rate, while both probiotic types improved feed conversion rate compared to the control animals, at the lower dose of multi-species (A1) and at the higher dose of mono-species (B2) probiotics. Body composition did not vary between treatments. At 4 weeks, ACH50 activity was significantly higher in fish fed higher dose of B probiotic (B2, 123.7 ± 50.6 vs 44.1 ± 7.7 U.ml-1 in control). At 8 weeks, lysozyme activity was higher in fish fed A1 (13.1 ± 5.2 μg ml−1) diet compared to fish fed control diet (7.8 ± 1 μg ml−1). Plasma peroxidase and head-kidney respiratory burst did not differ among the dietary treatments. Villi length and integrity and goblet cell counting of a cross section of the anterior intestine were not significantly different between groups.
Results suggest benefits in zootechnical performance and immune humoral responses using both probiotic types, in a dose dependent manner, without apparent alterations in intestinal morphology.
•Two commercial probiotics were studied in rainbow trout.•Both probiotics altered the innate immune responses.•Both probiotics improved growth performance after 8 weeks of treatment.
This study aimed to evaluate the protective effects of four autochthonous bacteria isolated from juvenile sole (Solea senegalensis) intestine as dietary probiotic supplement against bacterial ...pathogen infection and handling/transport stressors. Growth performance and immune responses were evaluated after 85 days of feeding trial. Sole (IBW = 16.07 ± 0.11 g) were fed six experimental diets, a control diet (CTRL, without the dietary probiotic supplementation), and five diets supplemented with probiotic bacteria: PB1 (Shewanella hafniensis), PB2 (Enterococcus raffinosus), PB3 (Shewanella hafniensis + Arthrobacter soli), PB4 (Pseudomonas protegens + Arthrobacter soli) and PB5 (Shewanella hafniensis + Arthrobacter soli + Enterococcus raffinosus). All bacteria were selected based on their in vitro antimicrobial activity. After the growth trial, fish were submitted to a stress factor (transport) and then each dietary group was divided in two additional groups: non-infected (placebo) and infected with Photobacterium damselae subsp. piscicida. Immune and antioxidant responses were evaluated at day 10 post-infection. In infection trial A, fish were infected on the same day of transport, whereas in trial B fish were infected after a 7-day recovery from the transport stress. At the end of the feeding trial, fish fed with PB2 and PB4 showed lower final body weight when compared with the other dietary groups. Respiratory burst activity and nitric oxide production were not affected by probiotic supplementation. Fish fed with PB5 presented lower peroxidase activity compared to CTRL. Lysozyme and alternative complement pathway activity (ACH50) showed no significant differences between treatments. The innate immune responses were significantly affected after handling stress and bacterial infection. In trial A, the ACH50 levels of infected fish were significantly lower than the placebo groups. On the other hand, in trial B fish infected with Pdp demonstrated higher ACH50 levels when compared to placebos. Peroxidase levels were strongly modulated by bacterial infection and handling stress. In trials A and B, infection had a clear downgrade effect in peroxidase levels. Lipid peroxidation, catalase, glutathione S-transferase and glutathione reductase were altered by both bacterial infection and transport.
Overall, dietary probiotic supplementation did not influence growth performance of sole. The immune and oxidative defenses of sole responded differently to infection depending on the probiotic and the synergy between pathogen infection and transport.
•Intestine autochthonous bacteria were used as probiotic in Senegalese sole.•Diets PB2 and PB4 resulted in lower final body weight compared with control.•Respiratory burst and nitric oxide were not affected by probiotic supplementation.•Oxidative stress and innate immunity were altered by handling and infection.
Dietary glycerol supplementation in aquaculture feed is seen as an alternative and inexpensive way to fuel fish metabolism, attenuate metabolic utilization of dietary proteins and, subsequently, ...reduce nitrogen excretion. In this study, we evaluated the impact of dietary glycerol supplementation on nitrogen excretion of European seabass (
Dicentrarchus labrax
) and its effects on metabolite profile and bacterial community composition of gut digesta. These effects were evaluated in a 60-day trial with fish fed diets supplemented with 2.5% or 5% (w/w) refined glycerol and without glycerol supplementation. Nuclear magnetic resonance spectroscopy and high-throughput 16S rRNA gene sequencing were used to characterize the effects of glycerol supplementation on digesta metabolite and bacterial community composition of 6-h postprandial fish. Our results showed that ammonia excretion was not altered by dietary glycerol supplementation, and the highest glycerol dosage was associated with significant increases in amino acids and a decrease of ergogenic creatine in digesta metabolome. Concomitantly, significant decreases in putative amino acid degradation pathways were detected in the predicted metagenome analysis, suggesting a metabolic shift. Taxon-specific analysis revealed significant increases in abundance of some specific genera (e.g.,
Burkholderia
and
Vibrio
) and bacterial diversity. Overall, our results indicate glycerol supplementation may decrease amino acid catabolism without adversely affecting fish gut bacterial communities.
Key points
• Glycerol can be an inexpensive and energetic alternative in fish feed formulations
.
• Glycerol did not affect nitrogen excretion and gut bacteriome composition
.
• Glycerol reduced uptake of amino acids and increased uptake of ergogenic creatine
.
• Glycerol reduced putative amino acid degradation pathways in predicted metagenome
.
A growth trial was conducted to evaluate the growth potential and nutrient utilization of Senegalese sole fed diets containing increasing replacement levels of dietary fishmeal (FM) by mixtures of ...plant protein (PP) sources. Six extruded isonitrogenous and isolipidic diets (55% crude protein and 8% crude fat on a dry matter basis) were fed to juvenile sole (mean initial body weight: 8
g
±
0.06) during 92
days. A reference diet containing FM as the main protein source (Control) was compared with five PP based-diets with increasing PP levels: 25% (PP25), 35% (PP35), 45% (PP45), 60% (PP60) and 75% (PP75). PP45, PP60 and PP75 diets were supplemented with crystalline amino acids to simulate the level present in the Control diet. The environmental impact of the tested diets was assessed through the determination of N and P budgets and calculating approximate Fish-in:Fish-out (Fi:Fo) ratios. Fish fed PP25 and PP75 reached a final body weight and daily growth index (DGI) similar to the Control group (P
>
0.05). Diet PP45 displayed the lowest DGI (0.8 vs 1.3%), lowest protein efficiency ratio (1.03 vs 1.8) and highest FCR (1.7 vs 1.01). The dietary treatments with highest percentage of FM replacement (PP60 and PP75) displayed similar FCR values as the Control (1.2–1.0). Apparent digestibility coefficients (ADCs) of protein varied between 77 and 85% and were not significantly affected by the PP inclusion level. Whole body protein and energy content did not differ significantly among treatments, but protein gain was significantly higher in the Control group compared to PP35, PP45 and PP60 groups. The results indicate that Senegalese sole can effectively cope with plant protein-based diets, but growth rate and nutrient gain mainly depend on the selection of adequate plant protein blends, rather than on the plant protein incorporation level. Sole fed the highest PP level (PP75) showed good growth performance, efficient dietary nutrient utilization and a lower Fi:Fo ratio compared to the Control. The present results clearly show that increasing FM replacement level can have a positive environmental impact as reduces P fecal waste and the fishmeal used per kg of sole produced.
► We tested increasing levels of dietary mixtures of plant protein (PP) sources. ► Senegalese sole can cope with PP-based diets. ► Growth rate and nutrient gain depend on the selection of adequate plant protein blends. ► Increasing FM replacement level has a positive environmental impact.
Senegalese sole (Solea senegalensis) is a highly valued flatfish that grows well with diets containing plant ingredients but their effects on immune competence is still a matter of debate. The ...current study aimed to examine changes in innate immune parameters and gut microbiota in Senegalese sole fed with 35% or 72% of plant ingredients with or without probiotic or yeast supplementation. Overall, fish fed diets with 72% of plant ingredients showed lower transcript levels of key immune- and stress-related genes in distal intestine, rectum and head-kidney than the 35% diets. In particular, hsp90b mRNA levels in distal intestine were down-regulated by 70% and 60% with the use of high content of plant ingredients in the diet containing the multispecies probiotic and autolyzed yeast, respectively. Denaturing gradient gel electrophoresis showed lower similarity values for distal intestine than rectum. Also fish fed high content of plant ingredients displayed lower similarity values, pointing to a difference in the microbial populations between fish fed different plant ingredient contents on the diet. Our data revealed that inclusion of plant ingredients was associated with differences in gene expression and a more diverse microbiota profile but without a significant effect on growth performance. Moreover, probiotic supplementation resulted in up-regulation of hsp90b, gpx, cat and apoa1 transcript levels in distal intestine concomitantly with a growth rate reduction compared to non-supplemented fish.
There is an increasing trend in the aquaculture industry to replace fishmeal for plant ingredients, as a means of promoting sustainability of the industry. This paper contributes significantly to our limited knowledge of how plant ingredients and supplements affect gut microbiota and immunocompetence.
•Increased inclusion of plant ingredients (PP) is associated with a more diverse gut microbiota profile.•Senegalese sole fed higher PP concentrations had lower immune- and stress-related transcript levels than the controls.•Multispecies bacteria supplementation resulted in up-regulation of genes involved in the antioxidative stress response.•Dietary probiotic supplementation had a negative impact on growth performance.
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