Exposure to High Aerial Ammonia Causes Hindgut Dysbiotic Microbiota and Alterations of Microbiota-Derived Metabolites in Growing Pigs

Ammonia, an atmospheric pollutant in the air, jeopardizes immune function, and perturbs metabolism, especially lipid metabolism, in human and animals. The roles of intestinal microbiota and its metabolites in maintaining or regulating immune function and metabolism are irreplaceable. Therefore, this study aimed to investigate how aerial ammonia exposure influences hindgut microbiota and its metabolites in a pig model. Twelve growing pigs were treated with or without aerial ammonia (35 mg/m3) for 25 days, and then microbial diversity and microbiota-derived metabolites were measured. The results demonstrated a decreasing trend in leptin (p = 0.0898) and reduced high-density lipoprotein cholesterol (HDL-C, p = 0.0006) in serum after ammonia exposure. Besides, an upward trend in hyocholic acid (HCA), lithocholic acid (LCA), hyodeoxycholic acid (HDCA) (p < 0.1); a downward trend in tauro-deoxycholic acid (TDCA, p < 0.1); and a reduced tauro-HDCA (THDCA, p < 0.05) level were found in the serum bile acid (BA) profiles after ammonia exposure. Ammonia exposure notably raised microbial alpha-diversity with higher Sobs, Shannon, or ACE index in the cecum or colon and the Chao index in the cecum (p < 0.05) and clearly exhibited a distinct microbial cluster in hindgut indicated by principal coordinate analysis (p < 0.01), indicating that ammonia exposure induced alterations of microbial community structure and composition in the hindgut. Further analysis displayed that ammonia exposure increased the number of potentially harmful bacteria, such as Negativibacillus, Alloprevotella, or Lachnospira, and decreased the number of beneficial bacteria, such as Akkermansia or Clostridium_sensu_stricto_1, in the hindgut (FDR < 0.05). Analysis of microbiota-derived metabolites in the hindgut showed that ammonia exposure increased acetate and decreased isobutyrate or isovalerate in the cecum or colon, respectively (p < 0.05). Unlike the alteration of serum BA profiles, cecal BA data showed that high ammonia exposure had a downward trend in cholic acid (CA), HCA, and LCA (p < 0.1); a downward trend in deoxycholic acid (DCA) and HDCA (p < 0.05); and an upward trend in glycol-chenodeoxycholic acid (GCDCA, p < 0.05). Mantel test and correlation analysis revealed associations between microbiota-derived metabolites and ammonia exposure-responsive cecal bacteria. Collectively, the findings illustrated that high ammonia exposure induced the dysbiotic microbiota in the hindgut, thereby affecting the production of microbiota-derived short-chain fatty acids and BAs, which play a pivotal role in the modulation of host systematic metabolism

Effects of Xylo-Oligosaccharides on Growth and Gut Microbiota as Potential Replacements for Antibiotic in Weaning Piglets.

Xylo-oligosaccharides (XOS) is a well-known kind of oligosaccharide and extensively applied as a prebiotic. The objective of this study was to investigate the effect of XOS supplementation substituting chlortetracycline (CTC) on growth, gut morphology, gut microbiota, and hindgut short chain fatty acid (SCFA) contents of weaning piglets. A total of 180 weaned piglets were randomly allocated to three treatments for 28 days, as follows: control group (basal diet, CON), basal diet with 500 mg/kg (XOS500) XOS, and positive control (basal diet with 100 mg/kg CTC). Compared with the CON group, the piglets in the XOS500 group improved body weight (BW) on days 28, average daily gain (ADG) and reduced feed: gain ratio during days 1-28 (P < 0.05). The XOS500 supplementation increased Villus height and Villus height: Crypt depth ratio in the ileum (P < 0.05). Villus Height: Crypt Depth of the ileum was also increased in the CTC treatment group (P < 0.05). Meanwhile, the XOS500 supplementation increased significantly the numbers of goblet cells in the crypt of the cecum. High-throughput 16S rRNA gene sequencing revealed distinct differences in microbial compositions between the ileum and cecum. XOS500 supplementation significantly increased the bacterial diversity. However, CTC treatment markedly reduced the microbial diversity (P < 0.05). Meanwhile, XOS500 supplementation in the diet significantly increased the abundance of Lactobacillus genus compared to the CON and CTC group in the ileum and cecum (P < 0.01), whereas the level of Clostridium_sensu_stricto_1, Escherichia-Shigella, and Terrisporobacter genus in the XOS500 group were markedly lower than the CON and CTC group (P < 0.05). In addition, dietary supplementation with XOS500 significantly increased the total short-chain fatty acids, propionate and butyrate concentrations and decreased the acetate concentration compared to the CON group in the cecum (P < 0.05). In summary, dietary supplemented with XOS500 could enhance specific beneficial microbiota abundance and decrease harmful microbiota abundance to maintain the structure of the intestinal morphology and improve growth performance of weaned piglets. Thus, XOS may potentially function as an alternative to in-feed antibiotics in weaned piglets in modern husbandry

Pectin supplementation ameliorates intestinal epithelial barrier function damage by modulating intestinal microbiota in lipopolysaccharide-challenged piglets.

peer reviewedDuring weaning, infants and young animals are susceptible to severe enteric infections, thus inducing intestinal microbiota dysbiosis, intestinal inflammation, and impaired intestinal barrier function. Pectin (PEC), a prebiotic polysaccharide, enhances intestinal health with the potential for a therapeutic effect on intestinal diseases. One 21-d study was conducted to investigate the protective effect of pectin against intestinal injury induced by intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS) in a piglet model. A total of 24 piglets (6.77±0.92 kg BW; Duroc × Landrace × Large White; barrows; 21 d of age) were randomly assigned into three groups: control group, LPS-challenged group, and PEC + LPS group. Piglets were administrated with LPS or saline on d14 and d21 of the experiment. All piglets were slaughtered and intestinal samples were collected after 3 h administration on d21. Pectin supplementation ameliorated the LPS-induced inflammation response and damage to the ileal morphology. Meanwhile, pectin also improved intestinal mucin barrier function, increased the mRNA expression of MUC2, and improved intestinal mucus glycosylation. LPS challenge reduced the diversity of intestinal microbiota and enriched the relative abundance of Helicobacter. Pectin restored alpha diversity and improved the structure of the gut microbiota by enriching anti-inflammatory bacteria and short-chain fatty acids (SCFAs)-producing bacteria, and increased the concentrations of acetate. In addition, Spearman rank correlation analysis also revealed the potential relationship between intestinal microbiota and intestinal morphology, intestinal inflammation, and intestinal glycosylation in piglets. Taken together, these results indicate that pectin enhances intestinal integrity and barrier function by altering intestinal microbiota composition and their metabolites, which subsequently alleviates intestinal injury and finally improves the growth performance of piglets

Taxifolin increased semen quality of Duroc boars by improving gut microbes and blood metabolites.

peer reviewedTaxifolin (TAX), as a natural flavonoid, has been widely focused on due to its strong anti-oxidation, anti-inflammation, anti-virus, and even anti-tumor activity. However, the effect of TAX on semen quality was unknown. The purpose of this study was to analyze the beneficial influences of adding feed additive TAX to boar semen in terms of its quality and potential mechanisms. We discovered that TAX increased sperm motility significantly in Duroc boars by the elevation of the protein levels such as ZAG, PKA, CatSper, and p-ERK for sperm quality. TAX increased the blood concentration of testosterone derivatives, antioxidants such as melatonin and betaine, unsaturated fatty acids such as DHA, and beneficial amino acids such as proline. Conversely, TAX decreased 10 different kinds of bile acids in the plasma. Moreover, TAX increased "beneficial" microbes such as Intestinimonas, Coprococcus, Butyrivibrio, and Clostridium_XlVa at the Genus level. However, TAX reduced the "harmful" intestinal bacteria such as Prevotella, Howardella, Mogibacterium, and Enterococcus. There was a very close correlation between fecal microbes, plasma metabolites, and semen parameters by the spearman correlation analysis. Therefore, the data suggest that TAX increases the semen quality of Duroc boars by benefiting the gut microbes and blood metabolites. It is supposed that TAX could be used as a kind of feed additive to increase the semen quality of boars to enhance production performance

Numerical Simulation of Wind Characteristics in Complex Mountains with Focus on Terrain Boundary Transition Curve

In recent years, an increasing number of projects have been developed in complex mountainous areas. The wind environment in mountainous areas, extremely complex due to the undulating terrain and diverse landscapes, is a key factor threatening the structural safety of buildings and their appurtenances in mountainous areas. Therefore, it is important to study the wind environment in complex terrain to clarify the wind resistance of structures in mountainous areas. Computational fluid dynamics (CFD) approaches are commonly used to examine wind fields in complex terrain; however, due to the limited range of terrain considered, direct modeling using terrain elevation data can result in truncated elevation differences, affecting the accuracy of numerical simulations. To address the problem of truncated elevation differences at terrain boundaries, the parameters of the wind tunnel contraction curve are optimized regarding the wind tunnel contraction section design principle. Moreover, several transition curves are analyzed and evaluated by numerical simulation methods, and a transition curve applicable to the terrain boundary transition form is proposed. The proposed terrain transition curves are applied to model the terrain of complex mountainous ski resort areas to be used in CFD numerical simulations. Furthermore, the accuracy of the numerical simulation is verified through a comparison with the field-measured data. Results indicate that the proposed method can accurately and effectively reflect the wind environment characteristics of a ski resort area. The proposed terrain transition curve provides a theoretical basis and case support for designing the terrain model boundary transition section, which can be used as a reference for wind tunnel and numerical simulation studies in complex mountainous areas

Seismic activities before and after the impoundment of the Xiangjiaba and Xiluodu reservoirs in the lower Jinsha River

The lower Jinsha River basin is located at the junction of Sichuan and Yunnan provinces in Southwest China, a region with intense tectonic movements and frequent moderate to strong seismic activities. Cascade hydropower stations have been constructed along the lower Jinsha River since 2012. However, research on the effect of the impoundment of large-scale cascade reservoirs in a river basin on local seismic activities is currently lacking. Accurately identifying earthquake locations is essential for studying reservoir-induced earthquakes. Analyzing the spatiotemporal migration process of seismic activities based on complete and precise earthquake relocation is fundamental for determining the fluid diffusion coefficient, constructing fault models for reservoir areas, identifying earthquake types, exploring earthquake mechanisms, and evaluating seismic hazards. The seismicity pattern in the Xiangjiaba and Xiluodu reservoir areas, where seismic activities had been weak for a long time, has changed with the successive impoundment of the two reservoirs, showing microseismic events and seismic clusters. We investigated the spatiotemporal characteristics of seismic activities in the Xiangjiaba and Xiluodu reservoir areas using the waveform cross-correlation-based double-difference relocation technique and the b-value analysis method. We discovered that seismic events after the impoundment of these two reservoirs exhibited different characteristics in different regions. The seismic activities at the Xiluodu dam quickly responded to the rising water level, with the seismic intensity decaying rapidly afterward. These events were concentrated in the limestone strata along both sides of the Jinsha River, with a shallow focal depth, generally within 5 km, and a high b-value of approximately 1.2. Such features are close to those of karst-type earthquakes. Microseismic activities frequent occur on the eastern bank of the Yongshan reservoir section downstream of the Xiluodu dam, with two parallel NW-trending earthquake strips visible after precise earthquake relocation. The MS5.2 earthquake near Wuji town on August 17, 2014, had prominent foreshocks and aftershocks distributed in a clear NW-trending 20-km-long strip, perpendicular to the riverbank. These seismic events had a low b-value of approximately 0.7. The orientation of the node plane revealed by the strike-slip focal mechanism of the mainshock is consistent with that of the strip formed by the foreshock-mainshock-aftershock sequence, indicating the existence of a NW-striking concealed fault. Seismic activities near the Yanjin-Mabian fault upstream of the Xiangjiaba reservoir area since 2013 were concentrated in a NW-trending strip, with several near EW-trending seismic clusters on its western side, and with the largest event having a magnitude of ML3.7. So far, the impoundment of the Xiangjiaba and Xiluodu reservoirs has not triggered seismic activities on the large Jinyang-Ebian and Yanjin-Mabian faults nearby

Spatiotemporal Characteristics of Reservoir-Induced Earthquakes Using P-Wave Velocity Structures

In this study, through the seismic phase observation report obtained by a river reservoir seismic network from September 2012 to July 2015, the joint inversion method of source and velocity structure is employed, combined with the regional seismic geological environment data. Such method gives the P-wave velocity structure of different sections in the reservoir area and tries to find out the impact range of the reservoir water depth. And the impact of reservoir water infiltration on crustal medium is discussed. The obtained location results show that the earthquake activity is mainly concentrated in the first reservoir tail and the second reservoir head. As such, the spatial distribution characteristics of the recorded earthquakes are given, and the resolution results of detection board at different depths are speculated and discussed

Optimal Combination of Aircraft Maintenance Tasks by a Novel Simplex Optimization Method

Combining maintenance tasks into work packages is not only necessary for arranging maintenance activities, but also critical for the reduction of maintenance cost. In order to optimize the combination of maintenance tasks by fuzzy C-means clustering algorithm, an improved fuzzy C-means clustering model is introduced in this paper. In order to reduce the dimension, variables representing clustering centers are eliminated in the improved cluster model. So the improved clustering model can be directly solved by the optimization method. To optimize the clustering model, a novel nonlinear simplex optimization method is also proposed in this paper. The novel method searches along all rays emitting from the center to each vertex, and those search directions are rightly n+1 positive basis. The algorithm has both theoretical convergence and good experimental effect. Taking the optimal combination of some maintenance tasks of a certain aircraft as an instance, the novel simplex optimization method and the clustering model both exhibit excellent performance

Effects of Bile Acids on Growth Performance and Lipid Metabolism during Chronic Heat Stress in Broiler Chickens

This study aimed to investigate whether dietary bile acid (BA) supplements can improve growth performance and lipid metabolism in heat-stressed broiler chickens. A total of 288 Arbor Acres broilers were blocked by BW and then randomly allocated into 4 treatments at 21 days of age. Birds reared under 32 °C had a higher cloacal temperature (p = 0.01), faster respiratory rate (p p = 0.016), average daily gain (ADG, p = 0.006), final body weight (FBW, p = 0.008), and feed conversion rate (FCR, p = 0.004). In heat stress (HS) birds, the breast muscle rate (p = 0.006) and pH 24 h postmortem (p = 0.065) were lower, and the shear force was higher (p = 0.027). Dietary BA supplements tended to increase the breast muscle rate (p = 0.075) without affecting the growth performance and serum lipids (p > 0.05). Serum total bile acid (TBA) was roughly duplicated after BA supplements (p = 0.001). In the liver, total cholesterol was lower (p = 0.046), and triglycerides were higher (p = 0.04) in the HS birds, whereas the expression of SREBP-1c showed an increasing trend (p = 0.06). In contrast, dietary BA decreased triglycerides and the expressions of hepatic SREBP-1c and FAS in the liver (p < 0.05). In summary, mild HS causes hepatic lipid accumulation without obvious tissue damages, whereas BA has positive effects on relieving abnormal lipid metabolism, indicating that BA as a nutritional strategy has a certain potential in alleviating HS

Role of Mitophagy in Regulating Intestinal Oxidative Damage

The mitochondrion is also a major site for maintaining redox homeostasis between reactive oxygen species (ROS) generation and scavenging. The quantity, quality, and functional integrity of mitochondria are crucial for regulating intracellular homeostasis and maintaining the normal physiological function of cells. The role of oxidative stress in human disease is well established, particularly in inflammatory bowel disease and gastrointestinal mucosal diseases. Oxidative stress could result from an imbalance between ROS and the antioxidative system. Mitochondria are both the main sites of production and the main target of ROS. It is a vicious cycle in which initial ROS-induced mitochondrial damage enhanced ROS production that, in turn, leads to further mitochondrial damage and eventually massive intestinal cell death. Oxidative damage can be significantly mitigated by mitophagy, which clears damaged mitochondria. In this review, we aimed to review the molecular mechanisms involved in the regulation of mitophagy and oxidative stress and their relationship in some intestinal diseases. We believe the reviews can provide new ideas and a scientific basis for researching antioxidants and preventing diseases related to oxidative damage