Microbiota Of Horses Research Articles

Current Understanding of Equine Gut Dysbiosis and Microbiota Manipulation Techniques: Comparison with Current Knowledge in Other Species.

Understanding the importance of intestinal microbiota in horses and the factors influencing its composition have been the focus of many studies over the past few years. Factors such as age, diet, antibiotic administration, and geographic location can affect the gut microbiota. The intra- and inter-individual variability of fecal microbiota in horses complicates its interpretation and has hindered the establishment of a clear definition for dysbiosis. Although a definitive causal relationship between gut dysbiosis in horses and diseases has not been clearly identified, recent research suggests that dysbiosis may play a role in the pathogenesis of various conditions, such as colitis and asthma. Prebiotics, probiotics, and fecal microbiota transplantation to modulate the horse's gastrointestinal tract may eventually be considered a valuable tool for preventing or treating diseases, such as antibiotic-induced colitis. This article aims to summarize the current knowledge on the importance of intestinal microbiota in horses and factors influencing its composition, and also to review the published literature on methods for detecting dysbiosis while discussing the efficacy of gut microbiota manipulation in horses.

The Microbiota and Equine Asthma: An Integrative View of the Gut-Lung Axis.

Both microbe-microbe and host-microbe interactions can have effects beyond the local environment and influence immunological responses in remote organs such as the lungs. The crosstalk between the gut and the lungs, which is supported by complex connections and intricate pathways, is defined as the gut-lung axis. This review aimed to report on the potential role of the gut-lung gut-lung axis in the development and persistence of equine asthma. We summarized significant determinants in the development of asthma in horses and humans. The article discusses the gut-lung axis and proposes an integrative view of the relationship between gut microbiota and asthma. It also explores therapies for modulating the gut microbiota in horses with asthma. Improving our understanding of the horse gut-lung axis could lead to the development of techniques such as fecal microbiota transplants, probiotics, or prebiotics to manipulate the gut microbiota specifically for improving the management of asthma in horses.

Microbiota characterization throughout the digestive tract of horses fed a high-fiber vs. a high-starch diet.

Diet is one of the main factors influencing the intestinal microbiota in horses, yet a systematic characterization of the microbiota along the length of the digestive tract in clinically healthy horses, homogenous for age and breed and receiving a specific diet is lacking. The study used 16S rRNA amplicon sequencing to characterize the microbiota of the intestinal tracts of 19 healthy Bardigiano horses of 14.3 ± 0.7 months of age fed one of two diets. Nine horses received a high-starch diet (HS), and ten horses received a high-fiber diet (HF). After 129 days, the horses were slaughtered, and samples were collected from the different intestinal tract compartments. The microbiota alpha diversity indices were lower in the caecum, pelvic flexure and right dorsal colon of the horses fed the HS diet (False Discovery Rate, FDR < 0.05). The values of beta diversity indicated significant compositional differences between the studied intestinal tract compartments according to the diet received (FDR < 0.05). At the lower taxonomic level (genus or family), the HS diet was associated with a higher relative frequency of Enterobacteriaceae within the small intestine (jejunum and duodenum) (FDR < 0.05). Within the hindgut (caecum and sternal flexure), the HS diet was associated with lower relative frequencies (i.e., a smaller core community) of bacteria belonging to Fibrobacteraceae and Prevotellaceae (FDR < 0.05). Moreover, horses fed the HS diet displayed a higher relative abundance of Streptococcus in the caecum (FDR < 0.05) and Fusobacterium in the sternal flexure (FDR < 0.05), both of which are pathogenic bacteria responsible for inflammation diseases. Samples collected from the pelvic flexure and rectum of horses fed the HS diet showed significantly higher relative frequencies of Succinivibrionaceae (FDR < 0.05) - amylolytic bacteria associated with acidosis. The relative frequencies of the Lachnospiraceae and Ruminococcaceae were lower in the feces collected from the rectum of horses receiving the HS diet vs. HF diet, indicating smaller core communities of these bacteria (FDR < 0.05). Fibrous diets should be promoted to prevent dysbiosis of the microbiota associated with high-starch diet.

Longitudinal effects of oral administration of antimicrobial drugs on fecal microbiota of horses.

Antimicrobial drug-associated diarrhea (AAD) is the most common adverse effect in horses receiving antimicrobials. Little information on how oral administration of antimicrobials alters intestinal microbiota in horses is available. Investigate changes of the fecal microbiota in response to oral administration of antimicrobials. Twenty healthy horses. Prospective, longitudinal study. Horses were randomly assigned to 4 groups comprising 4 horses each: group 1 (metronidazole); group 2 (erythromycin); group 3 (doxycycline); group 4 (sulfadiazine/trimethoprim, SMZ-TMP); and group 5 (control). Antimicrobials were administered for 5 days. Fecal samples were obtained before (day 0) and at 1, 2, 3, 4, 5, 6, and 30 days of the study period. Fecal microbiota was characterized by high throughput sequencing of the V4 region of the 16S rRNA. Horses remained healthy throughout the study. Richness and diversity in doxycycline, erythromycin, and metronidazole, but not SMZ-TMP groups, was significantly lower (P < .05) at multiple time points after administration of antimicrobials compared with samples from day 0. Main changes in the microbiota were observed during the time of antimicrobial administration (day 2-5; weighted and unweighted UniFrac PERMANOVA P < .05). Administration of erythromycin, doxycycline and, to a lesser extent, metronidazole produced a pronounced alteration in the microbiota compared with day 0 samples by decreasing the abundance of Treponema, Fibrobacter, and Lachnospiraceae and increasing Fusobacterium and Escherichia-Shigella. Oral administration of antimicrobials alters the intestinal microbiota of healthy horses resembling horses with dysbiosis, potentially resulting in intestinal inflammation and predisposition to diarrhea.

Exploring the Influence of Growth-Associated Host Genetics on the Initial Gut Microbiota in Horses.

The influences of diet and environmental factors on gut microbial profiles have been widely acknowledged; however, the specific roles of host genetics remain uncertain. To unravel host genetic effects, we raised 47 Jeju crossbred (Jeju × Thoroughbred) foals that exhibited higher genetic diversity. Foals were raised under identical environmental conditions and diets. Microbial composition revealed that Firmicutes, Bacteroidetes, and Spirochaetes were the predominant phyla. We identified 31 host-microbiome associations by utilizing 47,668 single nucleotide polymorphisms (SNPs) and 734 taxa with quantitative trait locus (QTL) information related to horse growth. The taxa involved in 31 host-microbiome associations were functionally linked to carbohydrate metabolism, energy metabolic processes, short-chain fatty acid (SCFA) production, and lactic acid production. Abundances of these taxa were affected by specific SNP genotypes. Most growth-associated SNPs are found between genes. The rs69057439 and rs69127732 SNPs are located within the introns of the VWA8 and MFSD6 genes, respectively. These genes are known to affect energy balance and metabolism. These discoveries emphasize the significant effect of host SNPs on the development of the intestinal microbiome during the initial phases of life and provide insights into the influence of gut microbial composition on horse growth.

9 Respiratory microbiota in horses are individual-specific rather than biogeographically variable

Respiratory disease in horses is associated with transportation, aspiration of oral contents, and primary infectious diseases, and has significant implications for both horse welfare and economic stability of equine industry. Regional conditions within the respiratory tract vary widely in temperature, nutrient availability, pH, and oxygen tension, creating different niches for microbial flora, some of which may not be identified by bacteriologic culture. Proliferation of commensal microbes likely contributes to initiation and progression of clinical disease. Understanding normal microbial populations is essential to investigating dysbiosis in the development of infectious respiratory disease. However, microbial populations within the equine lung have not been investigated with next generation sequencing technologies. Therefore, the study objective was to describe microbial population variability between respiratory tract locations in healthy horses. Samples were collected from 4 healthy adult horses, 2 mares and 2 geldings, aged 10–25 years, Thoroughbred, Standardbred, and Warmblood (2) breeds. Additional inclusion criteria were no history of respiratory or systemic disease within 2 mo of study, and no transportation within 1 week of sample collection at the University of Illinois Veterinary Teaching Hospital. Samples were collected by nasopharyngeal lavage (NPL) and transtracheal aspirate (TTA) premortem, and bybronchoalveolar lavage (BAL) of 6 distinct regions within the lung immediately post-mortem. Microbial DNA was extracted and full-length 16S ribosomal DNA sequencing was performed, followed by microbial profiling analysis with TADA Nextflow and R. There was a large amount of diversity, with over 1800 taxa identified, reduced to 160 taxa after prevalence filtering. The number of taxa and diversity were highly variable across sample locations. Actinobacteria, proteobacteria, and firmicutes were the predominant phyla. There was no significant difference in α or β diversity between the 3 sampling locations (NPL, TTA, BAL). When NPL and TTA were combined, there was a significant difference in α diversity compared with lung for Chao1, ACE and PD indices. There was significant difference in β diversity between horses. Overall, microbiota in respiratory samples of heathy horses were highly variable. Taxa were more similar between regions within the same horse, than between the same region of different horses, suggesting that respiratory microbiota are unique to individuals. These findings do not support presence of a core respiratory microbiome across individuals.

85 Can feces be used to represent the cecal microbiota in horses?

The fecal microbiota has been accepted as representative of the microbiota of horses' large intestine, but it is important to know which compartment the fecal microbiota most resembles, since the composition of the microbiota changes in each compartment. The study's aim was to compare fecal and cecal microbiota in to determine if the former provides a reasonable approximation of the latter. The Ethics Committee on Animal Research (2057/21-FCAV/UNESP) approved this study. In a 3-way Crossover Design, 5 healthy mixed-breed horses (BW: 384 ± 9.5 kg) were fed 3 different diets: hay, fiber and oil (FO), and sugar and starch (SS). Diets with added concentrate (FO and SS) kept the proportion of dry matter from hay at 1.5%/BW and concentrate at 0.5%/BW. Rectal sampling was used to collect feces, and cecal fluid samples were obtained from a cecal cannula. The microbiota was identified using Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene. DADA2 was used to analyze the data (version 1.24.0). We used the Shannon index and the Chao1 index for α diversity, and Jaccard and Bray-Curtis for β diversity (abundance). DADA2 was used to assess the statistical significance of diversity metrics. Regardless of diet, the microbiota in the cecum and feces showed differences in diversity and abundance (P < 0.01). The Jaccard and Bray distances between the cecum and the feces were 57.4% and 48.4%, respectively, indicating a difference between the 2 sites studied.There was no phylum difference between diets (P > 0.01). The most abundant phyla in the cecum were Proteobacteria, Verrucomicrobiota, and Desulfobacterota, which differed from the literature (Bacteroidota and Firmicutes). Proteobacteria is commonly found in the ilium, and it is possible that the phylum gained access to the cecum through extravasation of this compartment. Furthermore, the positioning of the cannula, closer to the ilium opening in the cecum, may have contributed to the finding of a greater abundance of this phylum. The Verrucomicrobiota is commonly found in the cecum, and little is known about the Desulfobacterota. In the feces, the most abundant phyla were similar to those previously reported, including Bacteroidota, Firmicutes, and Fibrobacterota. The large difference between the microbiota of the cecum and the feces can be attributed to the greater distance between the collection sites, as it is known that the microbiota composition changes in each compartment. The fecal microbiota is an overview of what happens in the large intestine but may not effectively represent other intestinal compartments. Finally, the fecal microbiota does not represent the cecal microbiota.

Topography of the respiratory, oral, and guttural pouch bacterial and fungal microbiotas in horses.

The lower respiratory tract microbiota of the horse is different in states of health and disease, but the bacterial and fungal composition of the healthy respiratory tract of the horse has not been studied in detail. The respiratory tract environment contains distinct niche microbiotas, which decrease in species richness at more distal sampling locations. Characterize the bacterial and fungal microbiotas along the upper and lower respiratory tract of the horse. Healthy Argentinian Thoroughbred horses (n=11) from the same client-owned herd. Prospective cross-sectional study. Eleven upper and lower respiratory tract anatomical locations (bilateral nasal, bilateral deep nasal, nasopharynx, floor of mouth, oropharynx, arytenoids, proximal and distal trachea, guttural pouch) were sampled using a combination of swabs, protected specimen brushes, and saline washes. Total DNA was extracted from each sample and negative control, and the 16S rRNA gene (V4) and ITS2 region were sequenced. Community composition, alpha-diversity, and beta-diversity were compared among sampling locations. Fungal species richness and diversity were highest in the nostrils. More spatial heterogeneity was found in bacterial composition than in fungal communities. The pharyngeal microbiota was most similar to the distal tracheal bacterial and fungal microbiota in healthy horses and therefore may serve as the primary source of bacteria and fungi to the lower respiratory tract. The pharynx is an important location that should be targeted in respiratory microbiota research in horses. Future studies that investigate whether biomarkers of respiratory disease can be reliably detected in nasopharyngeal swab samples are warranted.

Comparative Analysis of Gut Microbiota Between Healthy and Diarrheic Horses.

Increasing evidence reveals the importance of gut microbiota in animals for regulating intestinal homeostasis, metabolism, and host health. The gut microbial community has been reported to be closely related to many diseases, but information regarding diarrheic influence on gut microbiota in horses remains scarce. This study investigated and compared gut microbial changes in horses during diarrhea. The results showed that the alpha diversity of gut microbiota in diarrheic horses decreased observably, accompanied by obvious shifts in taxonomic compositions. The dominant bacterial phyla (Firmicutes, Bacteroidetes, Spirochaetes, and Kiritimatiellaeota) and genera (uncultured_bacterium_f_Lachnospiraceae, uncultured_bacterium_f_p-251-o5, Lachnospiraceae_AC2044_group, and Treponema_2) in the healthy and diarrheic horses were same regardless of health status but different in abundances. Compared with the healthy horses, the relative abundances of Planctomycetes, Tenericutes, Firmicutes, Patescibacteria, and Proteobacteria in the diarrheic horses were observably decreased, whereas Bacteroidetes, Verrucomicrobia, and Fibrobacteres were dramatically increased. Moreover, diarrhea also resulted in a significant reduction in the proportions of 31 genera and a significant increase in the proportions of 14 genera. Taken together, this study demonstrated that the gut bacterial diversity and abundance of horses changed significantly during diarrhea. Additionally, these findings also demonstrated that the dysbiosis of gut microbiota may be an important driving factor of diarrhea in horses.

Characterisation of faecal microbiota in horses medicated with oral doxycycline hyclate.

Antimicrobial-associated diarrhoea is a common adverse effect of antimicrobial treatment in horses and has been reported following the administration of oral doxycycline. The administration of antimicrobials has also been associated with changes in the equine intestinal microbiota diversity yet has not been explored under doxycycline treatment. To describe the dynamics of the faecal microbial diversity following a 5-day oral administration of doxycycline in healthy horses with Streptococcus zooepidemicus infected tissue chambers. Experimental prospective cohort study in a single horse group. Seven healthy adult horses with S. zooepidemicus infected tissue chambers received oral doxycycline at 10mg/kg q 12h for 5-days following the tissue chamber inoculation. Faeces were collected prior to the tissue chamber inoculation and until 28-days post inoculation. Faecal microbiota was characterised by high throughput sequencing of the V4 region of the 16S rRNA gene on the Illumina MiSeq sequencing platform. Bioinformatic analysis was performed with Mothur and statistical analysis were conducted on R Studio. A significant decrease in alpha diversity, characterised by a decrease of richness and diversity, and a decrease in beta diversity, characterised by changes in relative abundance, occurred after initiation of and during the administration of doxycycline. A decrease in Verrucomicrobia and increase in Firmicutes:Bacteroidetes ratio occurred following the initiation of treatment, with a return to initial Firmicutes:Bacteroidetes ratio during the treatment. It took 23days after discontinuing the treatment for the faecal microbiota to return close to the initial state. Lack of control population within the study. Transitory intestinal dysbiosis occurs under oral administration of doxycycline in horses.

Caecal microbiota in horses with trigeminal-mediated headshaking.

BackgroundTrigeminal‐mediated headshaking (TMHS) in horses is a form of neuropathic pain of undetermined cause that often results in euthanasia. The role of microbiota in TMHS has not been investigated in diseased horses.ObjectiveTo investigate if gastrointestinal microbiota in the cecum is different in horses with TMHS compared to a control population, during a summer season with clinical manifestations of disease.AnimalsTen castrated horses: five with TMHS and five neurologically normal controls.MethodsAll horses were sourced from our institution and kept under the same husbandry and dietary conditions. All horses were fed orchard grass hay for 30 days and then were euthanized due to chronic untreatable conditions including TMHS and orthopedic disease (control group). Caecal samples for microbiota analysis were collected within 20 min after euthanasia. Sequencing was performed using an Illumina MiSeq platform and the microbiome was analyzed.ResultsThe caecal microbiota of horses with TMHS was similar to control horses in terms of diversity but differed significantly with Methanocorpusculum spp. having higher abundance in horses with TMHS. Conclusions and clinical importance Methanocorpusculum spp. was more abundant in the cecum of horses with TMHS. However, its role in disease is unknown. Furthermore, it could also represent an incidental finding due to our small population size.

EquineReview

Introduction: This month's Equine Review presents papers on a large prospective European study of the efficacy and safety of the glucocorticoid prodrug ciclesonide, changes in the faecal microbiota of horses hospitalised for colic and the comparison of chlorhexidine and alcohol-based antisepsis of the equine distal limb.

Nasopharyngeal bacterial and fungal microbiota in normal horses and horses with nasopharyngeal cicatrix syndrome.

BackgroundThe nasopharyngeal bacterial and fungal microbiota of normal horses and those with nasopharyngeal cicatrix syndrome (NCS) are unknown.Hypotheses/ObjectivesTo describe the microbiota from nasopharyngeal washes of healthy horses and of horses acutely affected with NCS.AnimalsTwenty‐six horses acutely affected with NCS horses and 14 unaffected horses.MethodsProspective, observational cohort study. Horses were recruited by investigators through personal communications in central Texas. Bacterial (16s RNA) and fungal (internal transcribed spacer) microbiota from nasopharyngeal washes were evaluated. Polymerase chain reaction for detection of Pythium insidiosum was performed.ResultsResults indicated that 6 fungal genera (Alternaria, Bipolaris, Microascus, Spegazzinia, Paraconiothyrium, Claviceps) and 1 bacterial genera (Staphylococcus) were significantly different between affected and unaffected horses. The fungal genus Bipolaris had increased abundance in NCS affected horses and on NCS affected farms. Pythium insidiosum was absent in the nasopharyngeal wash of all horses, irrespective of health status.Conclusion and Clinical ImportanceSignificant differences were identified in the fungal microbiota in horses affected with NCS and farms affected with NCS compared to those unaffected. Therefore, Bipolaris warrants further investigation.

Factors influencing the composition and balance of foals’ microbiota

Horses are extremely dependent on the correct functioning of the digestive system for energy production and the performance of their physiological functions. The intestinal microbiota plays a key role in maintaining health, being related to the modulation of the immune system, protection against pathogenic microorganisms and also for obtaining nutrients. Due to the importance of the microbiota in maintaining health from the beginning of life, this review aims to address the early composition, development and factors that influence the intestinal microbiota in foals. A qualitative review was carried out in the main research databases. Data referring to the early microbial colonization suggest that it occurs since intrauterine life, despite the fact that at birth, the foals acquire a large part of the microorganisms that will form its microbiota. The main phyla involved in this process are Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, which are aquired from a combination of bacteria present in the feces, vagina and other maternal environments. From birth until the first weeks of life, the microbiota gradually changes due to several factors, which include the composition of food, coprophagy, exposure to different environments and medications. The foal's microbiota becomes more stable in the first and second months of life. It is suggested that changes in the composition (dysbiosis) and diversity of the different phyla are a risk factor for the development of diseases, since the microbiota directly influences the immune system. From advances in sequencing technologies it was possible to investigate the components and factors associated with early colonization of microbiota in horses as well as factors related to the development of dysbiosis and disease. Nevertheless, many facts are still unclear and should be adressed in the future.

Effects of Pasture Grass, Silage, and Hay Diet on Equine Fecal Microbiota.

Simple SummaryThe intestinal microbial community in horses is very complex and interacts closely with diets. Apart from traditional forage diets, such as hay and pasture grass, silage is used to feed horses in China and other areas of the world for economic reasons or convenience of storage. Additionally, silage is also used for its convenience of harvesting and its nutrient components, including lactic acid and volatile fatty acids. In this study, we detected the characteristic composition of a fecal microbial community in horses that were fed silage with the use of a relatively new sequencing technique; we compared this result with that from horses that were fed hay and pasture grass. This study revealed some characteristic findings on the fecal microbial composition in horses that were given each of type of diet and showed significant differences between the groups. Our results provided novel data about the fecal microbial composition in horses on the silage diet. We hope that these could help balance the intestinal microbiota in horses that are mainly fed silage in combination with other types of forages in order to maintain intestinal health.Diet is an important factor affecting intestinal microbiota in horses. Fecal microbiota is commonly used as a substitute for studying hindgut microbiota when investigating the relationship between intestinal microbial changes and host health. So far, no study has compared the difference between the fecal microbiota found in horses that are fed pasture grass, silage, and hay. The present study aims to characterize the fecal microbiota in horses that were exclusively on one of the three forage diets, and to analyze the potential impact of these forages, especially silage, on horse intestinal health. There were 36 horses randomly assigned to each of the three groups; each group was fed only one type of forage for 8 weeks. High throughput sequencing was applied to analyze the bacterial taxa in fecal samples collected from the horses at the end of the feeding trial. The Lachnospiraceae family was statistically more abundant in horses fed with hay, while it was the least abundant in horses fed with silage. The Streptococcaceae spp., considered a core microbial component in equine intestinal microbiota, were present in significantly lower quantities in feces from horses that were fed pasture grass as compared to those from horses fed hay or silage. The novel data may help promote the balancing of horse intestinal microbiota and the maintenance of intestinal health in horses.

The Fecal Bacterial Microbiota in Horses with Equine Recurrent Uveitis.

Simple SummaryEquine recurrent uveitis (ERU) is an immune-mediated disease characterized by recurrent episodes of intraocular inflammation. Despite being a major cause of blindness in horses worldwide, the exact pathogenesis of ERU remains unknown. Recently, changes in the normal balance of the gastrointestinal tract bacteria (also known as dysbiosis) have been described in several immune-mediated diseases in humans, including uveitis. As such, the objective of this study was to compare the fecal bacterial community (the fecal microbiota) of horses with ERU with that of healthy horses living on the same farms. Study results revealed no significant alterations in the fecal microbiota between horses with ERU and healthy horses housed in the same environment. In order to better determine if there is an association between dysbiosis and ERU, future investigations are warranted to more specifically compare the fecal microbiota of horses that are having active flare-ups of ERU with that of horses in a quiescent period of the disease and with healthy horses.The objective of this study was to describe and compare the fecal bacterial microbiota of horses with equine recurrent uveitis (ERU) and healthy horses using next-generation sequencing techniques. Fecal samples were collected from 15 client-owned horses previously diagnosed with ERU on complete ophthalmic examination. For each fecal sample obtained from a horse with ERU, a sample was collected from an environmentally matched healthy control with no evidence of ocular disease. The Illumina MiSeq sequencer was used for high-throughput sequencing of the V4 region of the 16S rRNA gene. The relative abundance of predominant taxa, and alpha and beta diversity indices were calculated and compared between groups. The phyla Firmicutes, Bacteroidetes, Verrucomicrobia, and Proteobacteria predominated in both ERU and control horses, accounting for greater than 60% of sequences. Based on linear discriminant analysis effect size (LEfSe), no taxa were found to be enriched in either group. No significant differences were observed in alpha and beta diversity indices between groups (p > 0.05 for all tests). Equine recurrent uveitis is not associated with alteration of the gastrointestinal bacterial microbiota when compared with healthy controls.

Effects of phenylbutazone alone or in combination with a nutritional therapeutic on gastric ulcers, intestinal permeability, and fecal microbiota in horses.

BackgroundGastrointestinal (GI) injury and dysbiosis are adverse events associated with nonsteroidal anti‐inflammatory drug (NSAID) use in horses. Phenylbutazone has been shown to alter GI barrier function both in vitro and ex vivo, but its effects on barrier function have not been assessed in vivo. In addition, the ability of nutritional therapeutics to prevent these changes is not known.ObjectiveOur objectives were to determine whether (a) phenylbutazone affected barrier function in vivo and (b) if phenylbutazone‐induced GI injury could be ameliorated by the use of a nutritional therapeutic.AnimalsThirty healthy horses were randomly assigned to 3 groups (n = 10 per group): control, phenylbutazone, or phenylbutazone plus nutritional therapeutic.MethodsThis study was conducted as a blinded, randomized block design. All horses were managed identically throughout the study period. Samples were collected throughout the study period to monitor fecal microbiota changes and gastric ulcers before and after treatment. Quantification of the bacterial 16S rRNA gene in blood was used as a marker of intestinal permeability.ResultsPhenylbutazone increased amounts of bacterial 16S rDNA in circulation 3.02‐fold (95% confidence interval [CI], 0.1.89‐4.17), increased gastric ulceration score by a mean of 1.1 grade (P = .02), and induced specific changes in the microbiota, including loss of Pseudobutyrivibrio of family Lachnospiraceae. These changes were attenuated by nutritional treatment.Conclusions and Clinical ImportanceCollectively, these findings suggest that phenylbutazone induces GI injury, including impaired barrier function, and that nutritional treatment could attenuate these changes.

Experimental crossover study on the effects of withholding feed for 24\u2009h on the equine faecal bacterial microbiota in healthy mares

BackgroundAn association between equine gastrointestinal disease causing colic signs and changes in faecal bacterial microbiota has been identified. The reasons for these changes and their clinical relevance has not been investigated. Withholding feed, which is an integral part of managing horses with colic, may contribute to the observed changes in the microbiota and impact interpretation of findings in horses with colic. Study objectives were, therefore, to determine the effect of withholding feed for 24 h on equine faecal bacterial microbiota in healthy mares to differentiate the effects of withholding feed from the changes potentially associated with the disease.ResultsSpecies richness and Shannon diversity (alpha diversity) were significantly lower at the late withheld (10–24 h post withholding feed) and early refed (2–12 h post re-feeding) time points compared to samples from fed horses (P < 0.01). Restoration of species richness and diversity began to occur at the late refed (18–24 h post re-feeding) time points. Horses having feed withheld had a distinct bacterial population compared to fed horses (beta diversity). Bacteroidetes BS11 and Firmicutes Christensenellaceae, Christensenella, and Dehalobacteriaceae were significantly increased in horses withheld from feed primarily during the late withheld and early refed time points. Bacteroidetes Marinilabiaceae and Prevotellaceae, Firmicutes Veillonellaceae, Anaerovibrio, and Bulleidia, and Proteobacteria GMD14H09 were significantly decreased in horses with feed withheld at late withheld, early refed, and late refed time periods (P < 0.01). Changes in commensal gut microbiota were not significant between groups.ConclusionsWithholding feed has a significant effect on faecal bacterial microbiota diversity and composition particularly following at least 10 h of withholding feed and should be taken into consideration when interpreting data on the equine faecal bacterial microbiota in horses.

PSIV-14 Fecal Microbiome of Horses Grazing Integrated Warm- and Cool-Season Grass Rotational Pasture Systems

Abstract The objective of this study was to characterize shifts in the fecal microbiota of horses grazing different forage types within integrated cool- and warm-season grass (CSG; WSG) pasture systems and to explore relationships between forage nutrients and microbial composition. Eight mares grazed integrated rotational systems containing mixed CSG and one of two WSG: bermudagrass or crabgrass. Fecal samples were collected after 2–3 weeks grazing WSG, CSG, and following an orchardgrass hay diet (HAY). Forage nutrients were determined by near-infrared spectroscopy and analyzed by two-way ANOVA in SAS (v.9.4). Following DNA extraction, 16S rRNA gene sequence analysis was conducted in QIIME 2 (v.2020.2) with Kruskall-Wallis tests for alpha diversity, Spearman correlation with forage nutrients, and taxonomic assignment with Greengenes. A random forest classifier and regressor determined ability to predict forage type and nutrients based upon bacterial composition. Statistical significance was set at p ≤ 0.05. Forage water-soluble carbohydrates (WSC) were greatest in CSG and lowest in WSG; neutral detergent fiber (NDF) was greater in HAY than CSG or WSG. Species richness and evenness (Shannon Index) was greater in horses adapted to WSG vs. CSG or HAY and was correlated with WSC (rs = -0.49) and ethanol-soluble carbohydrates (ESCrs = -0.62). The random forest classifier resulted in model accuracy of 1.0 and identified amplicon sequence variants (ASV) most important in prediction of forage type. Sixteen ASV were from the order Clostridiales including Lachnospiraceae, Ruminococcacceae, and Veillonellaceae families and the genus Coprococcus. Other important taxa included Prevotella spp., Streptococcus luteciae, and Fibrobacter succinogenes. The regressor accurately predicted WSC (r2 = 0.95) and ESC (r2 = 0.84), but not NDF (r2 = 0.09). These results suggest that the equine hindgut microbiome is impacted by forage type and soluble carbohydrate content; however, further research is required to determine functional and physiological significance in grazing horses.

Effect of oral administration of omeprazole on the microbiota of the gastric glandular mucosa and feces of healthy horses.

BackgroundOmeprazole administration is associated with changes in gastric and fecal microbiota and increased incidence of Clostridioides difficile enterocolitis in humans and dogs.Hypothesis/ObjectivesStudy purpose was to assess the effect of omeprazole on gastric glandular and fecal microbiota in healthy adult horses.AnimalsEight healthy horses stabled on straw and fed 100% haylage.MethodsProspective controlled study. Transendoscopic gastric glandular biopsies, gastric fluid, and fecal samples were obtained from each horse twice at a 7‐day interval before the administration of omeprazole. Samples were taken on the same horses before and after a 7‐day administration of omeprazole (4 mg/kg PO q24h). pH was assessed on fresh gastric fluid and other samples were kept at −20°C until analysis. Bacterial taxonomy profiling was obtained by V1V3 16S amplicon sequencing from feces and gastric glandular biopsies. Analysis of alpha, beta diversity, and comparison between time points were performed with MOTHUR and results were considered significant when P < .05.ResultsGastric pH increased significantly after 7 days of omeprazole administration (P = .006). Omeprazole did not induce significant major changes in composition of fecal or gastric glandular microbiota, however, after administration, certain microbial genera became more predominant in the gastric glandular mucosa (lower Simpson's evenness, P = .05). Only the genus Clostridium sensu strictu_1 had a significant shift in the glandular gastric mucosa after omeprazole administration (P = .002). No population shifts were observed in feces.Conclusions and Clinical ImportanceOral administration of omeprazole could have fewer effects in gastrointestinal microbiota in the horse compared to other species.