Gastric Ulceration in Horses Exposed to Training and Activities Typical for Recreational Showing

Activities that are typical in the training and use of horses for recreational showing can induce gastric ulcers within 5 - 7 days. Intensive training and management conditions are not necessary for ulcers to develop in horses.

1. Introduction

Equine Gastric Ulcer syndrome (EGUS) has been shown to be highly prevalent in horses used for many competitive activities including racing [1-4], dressage and show jumping [5,6], endurance [7], and Western performance [8]. Ulcer prevalence rates in these horses have ranged from 40% to 93%; and the highest prevalence of ulcers is found in racing horses. Based on the results of these and other studies [9,10], it has been generally considered that EGUS is primarily a disorder of horses in intensive training, usually at a professional level. However, it was reported that 37% of horses used for light activities had gastric lesions [1], and many horses presented for examination for EGUS are not stereotypical of horses at risk for EGUS.

The horses reported here were exposed to conditions that are typical in the training and use of horses for recreational showing, including transportation, stall confinement with twice daily feeding, and light exercise. The purpose was to determine if these factors taken collectively are associated with the development of gastric ulcers.

2. Materials and Methods

Two study groups were involved, and in both groups, gastroscopic findings before and at the conclusion of each study were used to determine the impact of the activities on the development of EGUS. In one study group, the effects of transportation, stall confinement, and light exercise (lunging) were examined, and in the second group, the impact of 7 days of light work using an automatic exerciser[a] was studied. All horses were maintained following standard animal use and care guidelines and within parameters of all applicable local regulations.

The first study group consisted of 20 young Paint horses (17 - 21 mo) with no gastric ulcers. Ten control horses were maintained in their paddocks on site with no changes in management parameters. Ten principal horses were transported in a trailer for 4 h on day 0 to another site, placed individually in stalls, fed 2 lb oats and 7 lb alfalfa twice daily, and trained to the lunge line and saddled twice daily for 3 full days. On day 4, they were transported for 4 h back to the original site in a trailer. On day 5, gastroscopic examinations were performed on all horses. Gastric lesion severity was scored as follows: 0, intact mucosal epithelium (can have reddening and/or hyperkeratosis); 1, small single lesion or small multifocal lesions; 2, large single lesion or large multifocal lesions; 3, extensive (often coalescing) lesions with areas of apparent deep ulceration [10]. Reddening and hyperkeratosis were recorded as present or absent. Changes in gastric lesion score between day 1 and day 5 were analyzed within and between groups. Incidences of reddening and hyperkeratosis were compared between groups. Incidences of gastric lesion, whether within or between groups, were analyzed using Fisher's exact test.

The second study group consisted of 15 Thoroughbred horses (2 - 10 yr) with no gastric ulcers as determined by endoscopic examination on study days 2 and 1. There was no control group. The horses were housed in individual stalls (12 horses) or in paddocks (3 horses), and they were fed 7 lb alfalfa and 5 lb 10% sweet feed twice daily. The horses were exercised once daily for 7 days using an automatic exerciser. The exercise routine consisted of a trot or slow lope for 15 - 18 min and 10 min walking.

3. Results

In the first study, the 10 horses that were transported and housed off site had a significantly (p < 0.05) higher incidence of hyperkeratosis and reddening of the gastric squamous mucosa than the 10 control horses. Two control horses and seven principal horses developed gastric squamous mucosal ulcers by day 5 (controls: mean grade = 0.2, range = 0-1; principals: mean grade = 0.9, range = 0-2). The ulcer scores of the principal horses increased significantly (p < 0.05) from day 1; the ulcer scores of the control horses did not increase significantly.

In the second study, which used the automatic exerciser, 11 of 15 horses developed gastric squamous mucosal ulcers (mean grade = 1, range = 0-3). Ten horses developed hyperkeratosis, and five horses developed mucosal reddening.

4. Discussion

While EGUS is often associated with intensive training and management conditions, the findings reported here show that horses trained and used for typical recreational activities are at risk of developing gastric ulcers. It was also shown that ulcers can develop within just a few days of initiating light to moderate activities. The interaction of multiple risk factors for EGUS that are typically experienced by horses used for recreational training and showing activities resulted in an increased incidence of gastric lesions within a short period of time. None of the risk factors were severe, and none of these factors alone has previously been reported to induce gastric ulcers in horses.

In these two groups, there were no clinical signs associated with gastric ulceration. One could consider that treatment may not be indicated in the absence of clinical signs. However, these data indicate that ulcers can develop quickly with environmental and training changes. Therefore, the use of an acid-pump inhibitor may be indicated during these periods.

In show horses, the prevalence of gastric ulcers was 58% of hunter/jumper [5] and 63% of dressage horses evaluated for poor performance [6] compared with 70% and 73%, respectively, found in the studies presented here. The mean ulcer score was 2.1 in the hunter/jumper and dressage horses [6] and 2.3 in Thoroughbred racehorses in training [4] compared with 0.9 in study 1 and 1.0 in study 2. It is possible that some of the horses healed, whereas other horses had increasingly severe ulcers over time.

All lesions observed in our horses were in the gastric squamous mucosa, and these are considered to be caused by excessive exposure of the mucosa to hydrochloric acid (HCl). The equine gastric squamous mucosa is highly sensitive to HCl, and in in vitro models, mucosal injury has occurred within 30 min of exposure to solutions acidified by HCl [11,12]. In a study of horses exercised on a treadmill, even light exercise resulted in increased exposure of the squamous mucosa to highly acidic gastric contents [13]. Our findings indicate that peptic injury to the equine gastric squamous mucosa occurs in horses performing light work and in horses exposed to conditions typical for recreational show activities. Horses used for routine recreational activities should be considered to be at risk for EGUS, and therefore, prevention or treatment should be considered.

The studies reported here were funded by Merial Limited, 3239 Satellite Boulevard, Duluth, GA 30096.

Footnotes

[a] Equi-ciser, Equi-Master Inc., Calgary, Alberta, Canada T0M 1X0.