Equine gastric ulcer syndrome (EGUS) poses a significant concern for performance horse owners, especially among racing populations. Omeprazole, the gold-standard treatment for equine squamous gastric disease (ESGD)—lesions in the upper part of the stomach—can be expensive and is available only by prescription. Given ESGD’s clinical and economic impact in racehorses, researchers have suggested an effective feed additive, such as magnesium oxide, could serve as a buffering option.

Manufacturers commonly include magnesium oxide in cattle supplements to control rumen pH. Researchers Claire Leleu, DV, PhD, founder of Equi-Test, and Anne Couroucé, DMV, PhD, Dipl. ECEIM, of Oniris-CISCO, both in France, evaluated the effects of magnesium oxide specifically on ESGD in 2-year-old French Trotters in active race training. They hypothesized that magnesium oxide-treated horses would have less severe ESGD ulcers than the controls.

Leleu and Couroucé split 42 horses into treatment and control groups, using a double-blinded, placebo-controlled study design. Two veterinarians performed gastroscopy on all horses on Day 0 and assigned an ESGD score from 0-4. In this system 0 meant an intact gastric mucosa; 1 referred to hyperkeratosis; 2, small single or small multifocal ulcers; 3, large single or large multifocal ulcers; and 4, extensive and/or coalescing ulcers with areas of deep ulceration. On Day 0 both the treatment and control groups had similar score distributions. Specifically, 30% of the horses received a score of 2, while 42.5% had scores of 3 or 4. These figures confirmed the high prevalence of ESGD in this population.

The research team fed custom pelleted feeds to the control and treatment groups, respectively, three times daily. The treatment version contained a blend of different sources of magnesium oxide, and it could not be distinguished from the control version. They initiated feeding the supplement 24 hours after initial gastroscopy and continued for 30 days, when veterinarians performed a second gastroscopy and scored all horses for ESGD again. Feed and training regimens remained consistent for all horses in the study to minimize confounding factors.

At Day 30 the researchers saw a significant decrease in the mean ESGD scores in the magnesium oxide group compared to the control group. This suggests the supplement was successful at increasing gastric pH and promoting healing of the gastric mucosa. The researchers also looked at oxidative stress markers in the form of plasma mean lipidic peroxides pre- and post-treatment.

On Day 30 they saw a decrease in mean lipidic peroxide in the magnesium oxide group compared to the control group, suggesting that another mechanism for the improved ESGD scores could be reduced oxidative stress and increased scavenging of free radicals.

The researchers suggested supplemented magnesium oxide as a potential promising therapy for ESGD. While the data clearly showed an overall decrease in ESGD severity in the study population, it did not show the average decrease in ESGD scores per horse, so the researchers said it was unclear if some horses improved dramatically and some not at all, or if most affected horses improved at a predictable rate with the treatment. This data would help individual horse owners gauge the potential success of the supplement for their specific animal. More research is also needed regarding the role of reducing oxidative stress in mitigating ESGD.

Leleu noted she and her colleagues conducted this study in 2021 and a similar one in 2022, also with very positive results, but the latter has not yet been published. “The product, Timride-Up, was launched on the French market in 2023, with great success,” she said. “Trainers are very satisfied with Timride-Up and many report also the strong cooling effect, in relation with the influence of magnesium on the nervous system.” She said the next step is getting the product to market in the United States, noting it is currently under testing at Thoroughbred and Standardbred breeding farms in Kentucky and New Jersey.

The study, “Effect of a blend of magnesium oxide on Equine Squamous Gastric Disease in young trotter horses under training,” appeared in the Journal of Veterinary Science in November 2023.

Editor’s note: The study was funded by Timab Magnesium, but the authors declare no conflicts of interest.