Gastric microbiome in horses with and without equine glandular gastric disease

Investigating the gastrointestinal physiology of mature horses with and without a history of cribbing behavior in response to feeding a digestive support supplement

Cribbing, a stereotypic oral behavior observed in horses, involves placing incisors on a fixed object, arching the neck, pulling against the object, and emitting an audible grunt. This behavior has been associated with gastrointestinal (GI) dysfunction and gastric ulceration. In this randomized crossover study, we investigated the impact of a GI support supplement (SPL) on the GI environment and physiology of four cribbing (CB) and four non-cribbing horses (NCB). Mature Quarter Horses, acclimated to individual stalls for 16 hours daily with paddock turnout in pairs for 8 hours per day, were randomly assigned to receive either the SPL or placebo for 21 days, followed by a 2-week washout period. Fecal and gastric samples were collected for pH determination and blood samples were analyzed for serum cortisol and gastrin levels. Endoscopic examinations assessed gastric ulcer severity, and cribbing frequency and bouts were recorded via video surveillance. Data were analyzed using a mixed-model ANOVA. Results showed no differences in fecal and gastric pH between cribbing statuses. However, an interaction between supplementation and cribbing status was observed for squamous mucosa ulcer scores (P=0.003). There were no differences in glandular mucosa ulcer scores, serum cortisol, serum gastrin, and crib-bite count between CB and NCB horses or between supplementation groups. Crib-bout duration did not differ with supplementation, but differences were found between periods (P<0.05) and hour ranges (P<0.001). Our findings suggest that the GI support supplement may not effectively address cribbing behavior or alter the GI environment in NCB or CB horses.

Field study examining the mucosal microbiome in equine glandular gastric disease

Equine glandular gastric disease (EGGD) is a common disease among athletic horses that can negatively impact health and performance. The pathophysiology of this EGGD remains poorly understood. Previous studies using controlled populations of horses identified differences in the gastric glandular mucosal microbiome associated with disease. The objective of this study was to compare the gastric microbiome in horses with EGGD and those without across multiple barns and differing management practices. We hypothesized that alterations in the microbiome of the gastric glandular mucosa are associated with EGGD. A secondary objective was to perform a risk factor analysis for EGGD using the diet and management data collected. Microbial populations of biopsies from normal pyloric mucosa of horses without EGGD (control biopsies), normal pyloric mucosa of horses with EGGD (normal biopsies) and areas of glandular mucosal disruption in horses with EGGD (lesion biopsies) were compared. Lesion biopsies had a different microbial community structure than control biopsies. Control biopsies had a higher read count for the phylum Actinomycetota compared to lesion biopsies. Control biopsies also had an enrichment of the genera Staphylococcus and Lawsonella and the species Streptococcus salivarius. Lesion biopsies had an enrichment of the genera Lactobacillus and Actinobacillus and the species Lactobacillus equigenerosi. These results demonstrate differences in the gastric glandular microbiome between sites of disrupted mucosa in horses with EGGD compared to pyloric mucosa of horses without EGGD. Risk factor analysis indicated that exercise duration per week was a risk factor for EGGD.

Diversity and functional prediction of fungal communities in different segments of mongolian horse gastrointestinal tracts

BACKGROUND

Anaerobic fungi are effective fibre-degrading microorganisms in the digestive tract of horses. However, our understanding of their diversity and community structure is limited, especially in different parts of the gastrointestinal tract.

RESULTS

For the first time, high-throughput sequencing technology was used to analyse and predict fungal microbial diversity in different parts of the gastrointestinal tract of Mongolian horses. The results revealed that the richness and diversity of fungi in the hindgut of Mongolian horses were much higher than those in the foregut. The foregut was dominated by Basidiomycota and Ascomycota, whereas the hindgut was dominated by Neocallimastigomycota and Basidiomycota. At the genus level, the relative abundance of many pathogenic fungi (Cryptococcus, Cladosporium, Alternaria, and Sarocladium) in the foregut was significantly higher than that in the posterior gut, indicating that Mongolian horses have strong disease resistance. The prediction of fungal function also showed significant differences in the fungal flora between the foregut and the hindgut. The fungi in Mongolian horses' foreguts were mainly pathologically nutritive and contained many animal and plant pathogens, particularly in the small intestine (jejunum and ileum). This indicates that the foregut may be the most important immune site in the digestive system of Mongolian horses, which explains the high disease resistance of Mongolian horses. The number of unassigned functional groups in the posterior gut was significantly higher than that in the anterior gut, indicating that the functions of fungal groups in the posterior gut have not been fully explored, and further studies are required in the future.

CONCLUSIONS

Analysis of high-throughput sequencing results revealed that the fungal composition varied greatly among different gastrointestinal tract segments in Mongolian horses, whose hindgut contains many anaerobic fungi involved in plant cellulose degradation. This provides important basic data for studying fungal diversity in the digestive system of healthy horses, which can be used for the health assessment of horses and provides clues for further research on the disease resistance and digestive capacity of horses, as well as a reference for the early diagnosis of intestinal diseases and innovative treatment methods.

Effect of diet composition on glandular gastric disease in horses

BACKGROUND

Nutritional factors are suggested to influence the incidence and severity of glandular gastric disease (GGD) in horses.

OBJECTIVES

To retrospectively assess whether dietary fermentable carbohydrates increase the severity of GGD and to prospectively evaluate whether the partial substitution of concentrates by dehydrated alfalfa would decrease GGD severity scores.

ANIMALS

In total, 82 trotters from 4 training centers exercised ≥5 days/week.

METHODS

Multicenter retrospective observational study, and prospective 2-arm randomized trial. Glandular mucosae were observed by gastroscopy and scored (0-4 severity scale) at day 0 (D0). Biochemical composition of the diet fed was compared between ulcerated and nonulcerated groups. After D0, horses either received the same diet (control, n = 41) or pelleted dehydrated alfalfa substituting 50% concentrates (alfalfa, n = 41). Glandular scores were recorded in both groups after 21 (D21) and 42 days (D42). The first end point was a successful outcome, defined as a horse with a glandular score of 2 to 4 on D0, decreasing to a score of 0 to 1 on days 21 or 42.

RESULTS

Horses scored 0 to 1 at D0 ingested more (P = .01) soluble sugars from concentrates than those scored 2 to 4 before D0 (77.5 g/kg BW; 95% confidence interval [CI]: 71.1-84.0, vs 59.1 g/kg BW; 95% CI: 48.0-70.3), whereas starch intake did not differ between groups (P = .24). Among horses scored 2 to 4 at D0, fewer were scored 2 to 4 in the alfalfa group (1 out of 6) compared with the control group (6 out of 6) at D42 (P = .02). Clinical success was 47.7 times more likely in horses fed alfalfa compared with horses in the control group (95% CI: 1.6-1422.8).

CONCLUSION AND CLINICAL IMPORTANCE

Relationships were found between diet composition and integrity of the glandular mucosa. Feeding pelleted dehydrated alfalfa could help to reduce the incidence and severity of GGD.

Current Topics in Medical Colic

The list of medical causes of acute or chronic colic in horses is extensive. The purpose of this article is to review 4 medical causes of equine colic with a focus on newer trends in treatment. The 4 topics selected include gastric impaction, gastric glandular disease, colon displacement, and inflammatory bowel disease.

Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens

Horses are large non-ruminant herbivores and rely on microbial fermentation for energy, with more than half of their maintenance energy requirement coming from microbial fermentation occurring in their enlarged caecum and colon. To achieve that, the gastro-intestinal tract (GIT) of horses harbors a broad range of various microorganisms, differing in each GIT segment, which are essential for efficient utilization of feed, especially to use nutrients that are not or little degraded by endogenous enzymes. In addition, like in other animal species, the GIT microbiota is in permanent interplay with the host's cells and is involved in a lot of functions among which inflammation, immune homeostasis, and energy metabolism. As for other animals and humans, the horse gut microbiome is sensitive to diet, especially consumption of starch, fiber, and fat. Age, breeds, stress during competitions, transportation, and exercise may also impact the microbiome. Because of its size and its complexity, the equine GIT microbiota is prone to perturbations caused by external or internal stressors that may result in digestive diseases like gastric ulcer, diarrhea, colic, or colitis, and that are thought to be linked with systemic diseases like laminitis, equine metabolic syndrome or obesity. Thus, in this review we aim at understanding the common core microbiome -in terms of structure and function- in each segment of the GIT, as well as identifying potential microbial biomarkers of health or disease which are crucial to anticipate putative perturbations, optimize global practices and develop adapted nutritional strategies and personalized nutrition.

Equine Gastric Ulcer Syndrome affects fitness parameters in poorly performing Standardbred racehorses

Introduction

Equine Gastric Ulcer Syndrome (EGUS) is a highly prevalent disorder in horses, which can be classified, based on the localization of the lesions, as Equine Squamous Gastric Disease (ESGD) or Equine Glandular Gastric Disease (EGGD). Although EGUS is recognized as a common cause of poor performance in racehorses, objective investigations about its relation with athletic capacity are lacking. Therefore, the present retrospective study aims to evaluate the associations between EGUS severity and some fitness parameters measured during an incremental treadmill test in Standardbred racehorses in training.

Methods

With this aim, data from 87 Standard bred racehorses which underwent a complete diagnostic evaluation for poor performance was reviewed. During gastroscopic examination, a 0-4 score was assigned to ESGD, while EGGD was evaluated for absence/presence; a total EGUS score was obtained by adding 1 point to ESGD score in horses showing concomitant EGGD. Fitness parameters obtained during incremental treadmill test included speed at a heart rate of 200 bpm (V200), speed and heart rate at a blood lactate of 4 mmol/L (VLa4, HRLa4), peak lactate, lactate and heart rate at 30 minutes post-exercise, maximum speed, minimum pH and maximum hematocrit. The associations between fitness parameters and EGUS and ESGD scores were evaluated by Spearman correlation, while Mann-Whitney test was used to compare them between horses with or without EGGD. Statistical significance was set at p<0.05.

Results

EGUS grade was inversely correlated with V200 (p = 0.0025) and minimum pH (p = 0.0469); ESGD grade was inversely correlated with V200 (p = 0.0025) and VLa4 (p = 0.0363). Although a trend was observed, no significant differences in V200 were observed between horses with or without EGGD (p = 0.073); horses with EGGD reached a lower minimum pH (p = 0.0087).

Discussion

These results show a negative association between aerobic capacity and EGUS, in particular ESGD. Although different hypotheses have been proposed, including abdominal pain and decreased appetite due to lactate accumulation, the underlying mechanisms are still unknown, and it is not clear whether EGUS represents a cause or a consequence of an early lactate accumulation and post-exercise acidosis.

Dietary and management factors influence the equine gastric microbiome

OBJECTIVE

The purpose of this study was to characterize the relationship of diet and management factors with the glandular gastric mucosal microbiome. We hypothesize that the gastric mucosal microbial community is influenced by diet and management factors. Our specific objective is to characterize the gastric mucosal microbiome in relation to these factors.

ANIMALS

57 client-owned horses in the southern Louisiana region with and without equine glandular gastric disease.

PROCEDURES

Diet and management data were collected via a questionnaire. Gastroscopy was used for evaluation of equine gastric ulcer syndrome and collection of glandular mucosal pinch biopsies. 16S rRNA amplicon sequencing was used for microbiome analysis. Similarity and diversity indices and sequence read counts of individual taxa were compared between diet and management factors.

RESULTS

Differences were detected in association with offering hay, type of hay, sweet feed, turnout, and stalling. Offering hay and stalling showed differences in similarity indices, whereas hay type, sweet feed, and turnout showed differences in similarity and diversity indices. Offering hay, hay type, and sweet feed were also associated with differences in individual sequence read counts.

CLINICAL RELEVANCE

This study provides preliminary characterization of the complex relationship between the glandular gastric microbiome and diet/management factors. The ideal microbiome to promote a healthy glandular gastric environment remains unknown.

A study comparing the healthy and diseased equine glandular gastric microbiota sampled with sheathed transendoscopic cytology brushes

BACKGROUND

The role of the equine gastrointestinal microbiota in the pathogenesis of equine glandular gastric disease (EGGD) is poorly understood.

OBJECTIVES

To investigate whether the glandular gastric microbiota is altered in horses with EGGD.

STUDY DESIGN

Prospective longitudinal study METHODS: Five Thoroughbred racehorses from one training centre underwent gastroscopy as part of poor performance investigation. Samples were taken from EGGD lesions and adjacent normal mucosa using sheathed transendoscopic cytology brushes and frozen at -80 °C. DNA was extracted for 16S rRNA sequencing, and sequences compared against a database to generate taxonomic classification of the microbiota. The same horses were sampled six months later.

RESULTS

Normal glandular mucosal samples were characterised by a higher proportion of Proteobacteria (46.3 %) than EGGD lesions (18.9 %). Relative abundance of Firmicutes was lower in samples from normal mucosa (20.0 %) than EGGD lesions (41.2 %). Linear discriminant analysis effect size (LEfSe) confirmed a greater proportion of Firmicutes species was characteristic of samples collected from EGGD lesions due to a very high relative abundance of Sarcina (up to 92.4 %) in two horses with EGGD. We were unable to comment on the stability of the glandular gastric microbiota over time.

MAIN LIMITATIONS

Small sample population. None of the horses examined had grossly normal gastric mucosa.

CONCLUSIONS

The gastric microbiota appears altered in EGGD, although we are unable to demonstrate a causative effect. Sarcina was particularly increased in abundance in EGGD and may be a useful biomarker of disease. Sheathed cytology brushes were an effective method for sampling the gastric mucosa.