低聚半乳糖干预缓解肠道炎症的研究进展

肠道炎症已成为我国社会健康的难题和挑战，其发病率在我国迅速增长。肠道炎症发病原因复杂，目前尚缺乏有效的缓解药物，因此加强肠道炎症有效缓解物质的研发至关重要。低聚半乳糖（galactooligosaccharide，GOS）是一种食疗益生性较优的乳源功能性低聚糖，能够有效促进肠道内益生菌的增殖，改变肠道菌群结构，刺激免疫应答，进而改善肠黏膜屏障功能，缓解肠道炎症。本文综述近年来国内外有关肠道炎症及GOS干预缓解肠道炎症作用的研究进展，并对其应用前景进行展望，为此领域的研究提供科学依据。     

Effect of Bacillus cereus as a water or feed additive on the gut microbiota and immunological parameters of Nile tilapia

We evaluated the effects of Bacillus cereus, as an additive in water and feed, on the gut microbiota and immunological parameters of Nile tilapia (Oreochromis niloticus) fingerlings. Experiments were performed in tanks and net cages respectively. Experiment 1: Tilapia were housed in tanks for 42 days, and B. cereus was added to the water at 1.0 × 10⁴ cfu mL^?1 (Treatment 1) and 1.0 ×10⁵ cfu mL^?1 (Treatment 2) weekly. For the control, no probiotic was added. Experiment 2: Tilapia were housed in cages for 42 days, and the feed was supplemented with B. cereus at 1.0 × 10⁷ cfu g^?1 (Treatment 1) and 1.0 × 10⁸ cfu g^?1 (Treatment 2) weekly. For the control, no probiotic was added. Each treatment contained three replicates, with 50 male tilapias per replicate. The fish from the probiotic treatments in both tank and cage experiments had significantly higher serum lysozyme and peroxidase activities than the control. In the cage experiment, alkaline phosphatase and total superoxide dismutase activities in tilapia were significantly higher in probiotic treatments compared with the control. The results of polymerase chain reaction‐denaturing gradient gel electrophoresis showed that B. cereus supplementation in the feed and water affected the autochthonous gut bacteria community of tilapia and stimulated various potentially beneficial bacteria. Therefore, B. cereus, as a water or feed additive, could enhance the immune status and affect the gut microbiota of tilapia. Bacillus cereus was more effective as a feed supplement rather than a water additive for enhancing the immune status of tilapia.     

Temperature modulates liver lipid accumulation in Atlantic salmon (Salmo salar L.) fed low dietary levels of long‐chain n‐3 fatty acids

Atlantic salmon (Salmo salar) were fed five graded levels of eicosapentaenoic acid (EPA, 20:5n‐3) and docosahexaenoic acid (DHA, 22:6n‐3), from 1.4 to 5.2% of total fatty acids (FA, 5–17 mg kg^?1 feed), and grew from ~160 g to ~3000 g, with the period from 1450 g onwards conducted both at 6 °C and at 12 °C. All fish appeared healthy, and there were no diet‐related differences in haematological or plasma parameters, as well as intestinal histological or gut microbiota analysis. Fish reared at 6 °C had higher accumulation of storage lipids in the liver compared to fish reared at 12 °C. Liver lipids also increased with decreasing dietary EPA + DHA at 6 °C, while there was no such relationship at 12 °C. Gene expression of SREBP1 and 2, LXR, FAS and CPT1 could not explain the differences in liver lipid accumulation. In liver polar lipids, DHA was found to be reduced when dietary EPA + DHA was <2.7% of FAs, while the level of EPA in the membranes was not affected. In conclusion, reducing dietary EPA + DHA from 5.2 to 1.4% of total FAs had a minor impact on fish health. Temperature was the factor that most affected the liver lipid accumulation, but there was also an interaction with dietary components.     

The influence of diet on the grass carp intestinal microbiota and bile acids

To elucidate the influence of different diet on the intestinal microbe and bile acids, we characterized the microbiota and bile acids in the hindgut content of grass carp fed on formula feed (FF group) or Sudan grass (SG group). Fusobacteria and Proteobacteria were significantly more represented in FF group than in SG group whereas Bacteroidetes was significantly more abundant in SG group than in FF group. Simpson diversity was significantly higher in FF group than in SG group (t = 2.33, P < 0.05). Chenodeoxycholic acid (CDCA) was the most abundant primary bile acid in the two groups, with average concentrations of 1.03 ± 0.62 and 4.44 ± 1.80 ng mg^?1 in SG and FF group respectively. The most abundant secondary bile acid was deoxycholic acid (DCA) in SG group and ursodeoxycholic acid (UDCA) in FF group, with average concentrations of 0.17 ± 0.06 and 2.67 ± 0.88 ng mg^?1 respectively. UDCA is significantly more abundant in FF group than in SG group, and the total bile acids were higher in FF group than in SG group. Cetobacterium and Fusobacteriaceae U114 were significantly related with the concentrations of CDCA (r = 0.85, P < 0.05 and r = 0.82, P < 0.05 respectively) and UDCA (r = 0.92, P < 0.01 and r = 0.92, P < 0.01 respectively). However, Bacteroides was negatively related with the concentration of UDCA (r = ?0.67, P < 0.05). Overall, there existed certain relationship between the intestinal microbes and the faecal bile acids, and they were both influenced by the diet.     

The effects of exogenous xylanase supplementation on the in vivo generation of xylooligosaccharides and monosaccharides in broilers fed a wheat-based diet

ABSTRACT

1. This study quantified xylanase-induced changes in soluble monosaccharides, xylooligosaccharides (XOS) and volatile fatty acid (VFA) contents of the different sections of the gastrointestinal tract (GIT) and whether these were related to altered bird performance.

2. An in vitro digestion of the wheat-based diet was carried out with the xylanase (Econase XT at 16,000BXU/kg diet) to compare the in vitro and in vivo generation of these XOS and monosaccharides. For the in vivo study, 80 male Ross 508 b roiler chicks were split into two groups fed a wheat-based diet with or without Econase XT (16,000BXU/kg diet) for 21 days.

3. There were no effects of Econase XT inclusion on growth performance characteristics, likely a result of the high-quality wheat diet, the corresponding high performance of the control group (FCR average of 1.45 in controls) and the relatively young age of the birds (from four to 26 days of age).

4. Econase XT supplementation increased the xylotetraose (X₄) content in the colon (P = 0.046, enzyme x GIT section interaction) and the xylose contents in the colon and caeca (P < 0.001, enzyme x GIT section interaction).

5. The trend for increased acetate production in the caeca of Econase XT treated birds (P = 0.062) suggested that the XOS generated were subsequently fermented in the caeca, potentially impacting upon the types of microbiota present.

6. The present study suggested that wheat arabinoxylan degradation was enhanced by xylanase supplementation, which may have increased the production of beneficial volatile fatty acids (VFA) in the caeca, and thereby potentially modulated the caecal microbiome, but without affecting bird performance at this early age.     

微生物菌群培养组学在动物医学中的应用

实验室条件下可培养的微生物约占自然界中微生物总数的1%，这限制了人们对99%未知微生物的认识和利用，而研究表明，那些“不可培养的微生物”是可以被开发和利用的，未能被纯培养的微生物才是未知微生物的主体。微生物培养组学探索利用多种培养条件和长时间的培养，结合基质辅助激光解吸电离飞行时间质谱法（MALDI-TOF-MS）和16S核糖体RNA（rRNA）测序可以大规模鉴定各种微生物，同时利用全基因组测序和宏基因组测序手段对未知微生物进行深入分析。本文综述了国内外近年来微生物菌群培养组学在反刍动物胃肠道、禽类盲肠及家畜鼻腔微生物菌群研究中的最新进展，探讨将动物体内菌群培养组学方法应用于动物疾病防治领域的可行性。作为一个新兴的研究方法，尽管该培养组学还存在一些不够成熟的方面，但它的发展前景十分广阔，微生物菌群培养组学方法和其他研究方法的互补已经逐渐成为发展兽医微生物学新的突破口。     

Sodium alginate supplementation modulates gut microbiota,health parameters,growth performance and growth‐related gene expression in Malaysian Mahseer Tor tambroides

This study investigated the effects of sodium alginate supplementation on gut microbiota composition, health parameters, growth performances and growth‐related gene expression of Malaysian mahseer. Five test diets were formulated by supplementing 0%, 0.1%, 0.2%, 0.4% and 0.8% sodium alginate. Triplicate groups of juvenile Tor tambroides (2.19 ± 0.05 g) were stocked in 15 aquaria (20 individuals per aquarium) and fed at 3.0% body weight per day for 60 days. PCoA and UPGMA analysis showed that gut bacterial community were more convergence in higher sodium alginate‐supplemented diets. The percentage of Porphyromonadaceae, Bacteroides, Plesiomonas and Shewanella were substantially higher and Aeromonas, Entomoplasmatales and Prevotellaceae were drastically lower in higher sodium alginate (0.2%–0.8%) diets. Sodium alginate supplementation (≥0.2%) significantly improved the haematocrit value and respiratory burst activity of T. tambroides. Growth performances and feed utilization were significantly higher in 0.2%–0.4% sodium alginate‐supplemented diets. The increased growth rate of T. tambroides was governed by both hyperplastic and hypertrophic muscle growth. Real‐time PCR data demonstrated that most of the growth‐related genes were significantly upregulated in 0.2%–0.4% sodium alginate‐supplemented diet. Finally, it can be concluded that sodium alginate should be supplemented at 2 g/kg in practical fish feed formulation.     

Formulated diet alters gut microbiota compositions in marine fish Nibea coibor and Nibea diacanthus

Nibea, an economical marine fish, is generally fed on trash fish (the low‐value fish), which can cause high feed costs and waste pollutions in high‐density aquaculture. To assess the effect of formulated diet on the gut microbiota in Nibea coibor and Nibea diacanthus, denaturing gradient gel electrophoresis, clone libraries analysis and Illumina sequencing of the 16S ribosomal RNA gene were used in this study. Two Nibea fishes were both dominated by Gammaproteobacteria (especially Photobacterium) and shared a set of gut microbiota, including Bacilli, Mollicutes, Alphaproteobacteria and Fusobacteriia. Statistical analyses revealed that formulated diet led to lower feed conversion ratio (p < 0.001), lower abundance of Vibrio (p = 0.040) and infectious diseases pathways (p = 0.001), higher abundance of polysaccharide‐degrading bacterium Cellvibrio (p = 0.006) in two Nibea species, with higher weight gain rate (p = 0.023) and microbial diversity (Shannon, p = 0.049 and Simpson, p = 0.044) and more carbohydrate metabolism (p = 0.020) observed in N. coibor. The distribution and correlation network of 17 potential short‐chain fatty acid producing bacteria were obtained and visualized in all treatment groups. The results reveal that formulated diet has beneficial effects on the gut microbial ecology in two Nibea fishes, which suggests the possibility of replacing trash fish diet with formulated diet in Nibea aquaculture.