Animal ethics
The study was performed in accordance with the New South Wales Department of Primary Industries guidelines for clinical studies and the New South Wales Animal Research Act of 1985. Informed consent from the owner, or the trainer acting as an agent for the owner, was obtained at the time of enrolment to the study.
Study design
A randomised, blinded, clinical study.
Recruitment and examination
Thoroughbred horses from 5 different stables were examined during July 2012. Prior to examination all horses were fed their normal evening feed, but any remaining food was removed 6 - 8 hours prior to endoscopy. Water was not withheld and horses were exercised normally on the morning of the examination at the trainers' discretion.
Horses were sedated with detomidine (10-20 μg/kg bwt IV)a and examined for the presence of gastric ulceration using a 3 meter flexible gastroscopeb. The squamous and glandular mucosa were scored separately using a 4 point scale as described by the EGUS council [21]. Based on the results of the gastroscopic examination, horses that met the inclusion criteria were enrolled into the study. Inclusion criteria for the study were horses with grade 2 or greater ulceration of the glandular mucosa, in race training and expected to remain in work for the next 4 weeks, not receiving any other medical treatment for EGUS and otherwise considered to be free of other significant disease.
Group allocation and blinding
Once enrolled into the study, horses were stratified by their existing trainer to reduce variability in the diet and management as these have been shown to be significant risk factors for glandular ulcer development [4]. Horses were then randomly allocated to receive either omeprazole alone (group OMEP) or omeprazole plus trimethoprim-sulphadimine (group TMPS) by pulling their names out of a hat. One investigator (KS) was responsible for randomization whilst the remaining investigators, including the principal investigator (BS) who undertook the gastroscopic examinations and scoring, remained blinded to the group allocation until scoring was completed and recorded. The trainers were not blinded to treatment group. The study protocol allowed for randomization to be broken in the event of an adverse event.
Treatment protocols
Horses were fed and exercised at the trainers' discretion driven by their normal routine, housed in individual stalls, bedded on wood shavings and fed a diet typical of Australian racehorses [22]. All horses were fed twice daily, with the morning feed typically within 2 hours of completing exercise, and the afternoon feed approximately 12-14 hours before exercising. All horses received 2 grams, equivalent to 4 mg/kg for a 500 kg horse, of a commercially available, enteric coated omeprazole paste formulationc PO 1 - 4 hours prior to morning exercise. At the same time, horses in group TMPS also received 15 grams, equivalent to a combined trimethoprim-sulphadimined dose of 30 mg/kg for a 500 kg horse, of a commercially available oral trimethoprim-sulfadimidine pasteg PO. To comply with the local regulations for racing, omeprazole was not administered on the day of racing.
Follow up endoscopy
Repeat gastroscopy, as described above, was scheduled between days 21 and 28. Some variation was allowed in the timing of the repeat gastroscopic examination to accommodate the horses' individual racing schedules. The squamous and glandular mucosa was scored and assessed separately for each horse. Where the starting grade was ≥ 2 for the particular mucosa, ulcer healing was defined as change to a grade of 0-1 as previously described [10]. Where a starting ulcer grade of ≥ 2 was present in the particular mucosa, horses were considered to have improved if the ulcer score for the region decreased by at least one grade. As previously described [23], where the starting score, for either the squamous or glandular mucosa, was ≥ 2 and subsequently changed to 0-1 the horse was considered to have both healed and improved for that mucosa as the definition of both improvement and healing had been met. Horses with a sub-maximal starting ulcer grade (<4) for the squamous or glandular mucosa were considered to have worsened if their ulcer grade for that particular mucosa increased by at least one grade.
Statistical analysis
As no data was available at the time of the study on the expected degree of healing of glandular ulceration with either omeprazole alone of the combination of omeprazole plus trimethoprim-sulfadimidine a power calculation was not performed. Instead the horses were enrolled on the basis of their availability.
Data was assessed for normality using D'Agostino and Pearson omnibus normality test. Data for age, weight and time between gastroscopic examinations in the 2 groups were normally distributed and 2-tailed unpaired Student T-tests were used to assess differences between the groups. All other data was not normally distributed. Genders between the two groups were compared using a two-sided Fisher's exact test. Baseline data for squamous and glandular ulcer scores were compared using a Mann Whitney U test. A Wilcoxon Paired Test was used to assess changes in ulcer scores within groups over time. A Mann Whitney U test was used to compare squamous and glandular ulcer scores overall and between the two groups. A Chi-squared analysis or Fisher's exact test (if >25% of entries had a frequency of 5 or less) were used to assess improvement or healing of ulcers.
Three commercially available statistical software packages were usede-g. The remaining 95% confidence intervals displayed use Jeffrey's intervals and were calculated using online statistical softwareg. Data is presented as mean ± SD if normally distributed and median and inter-quartile ranges (IQR) if not normally distributed. Odds ratios and 95% confidence intervals are displayed for binomial data. Significance was determined when p < 0.05.