Q: My mare has a history of equine gastric ulcer syndrome (EGUS). She’s currently at a training barn where several horses receive aloe vera juice (administered orally) to treat ulcers. The trainer would like my mare to be on it too. I visited the Mayo Clinic website and it lists several serious side effects caused to humans by taking aloe vera, which include bleeding, metabolic issues, diarrhea, and stomach cramping. These all seems like they would be bad for a horse prone to gastric ulcers. Is there any research that shows aloe vera is safe to administer to horses or that it helps EGUS? — via email
A: This is an interesting question and generally brings up the theme of evidence-based medicine and use of supplements for horses. Overall, any standard of care should include “do no harm” as a principle, followed by a hopeful therapeutic or preventive effect.
In the equine industry, we are frequently in a position of not having a great deal of information about treating horses, so many things are done off label or with limited evidence from other areas of medicine. The use of aloe vera for treatment or prevention of stomach ulcers falls into the latter category—we have limited evidence of effect of aloe vera, primarily in lab studies. For example, aloe vera has been shown to limit ulcer formation in rats in response to ethanol administration.
Using PubMed as my search tool, I found one published study comparing administration of aloe vera to omeprazole in horses with gastric ulcers (Bush, et al., Equine Veterinary Journal 2018;50:34-40). The dosage of aloe vera was 17.6 mg/kg, which was extrapolated from a dosage used in rats, and this was compared to the standard dose of omeprazole (4mg/kg) in a blinded trial of horses with gastric ulcers. The conclusion was that aloe vera was inferior to omeprazole. No side effects of aloe vera were reported.
Overall, my opinion is that if you suspect ulcers, have your horse endoscoped. If there are ulcers present, the proton pump inhibitor (PPI) labeled for use in horses (omeprazole) is the standard of care. A PPI at a lower dose is also the standard of care for prevention of ulcers. There are also an increasing number of performance horses that have ulcers that are refractory to PPI treatment, which may benefit from additional treatment with misoprostol. Importantly, an endoscopy would be even more critical to make this determination, including a full evaluation of the pylorus and proximal duodenum (initial part of the small intestine).
From more of a practical point of view, I think you can best avoid ulcers by maximizing forage (such as grass and hay) intake and minimizing soluble carbohydrate (as found in sweet feed). Pelleted feeds that also contain some roughage are preferable. It helps to remember that horses have a gastrointestinal tract designed for relatively consistent intake of forage and, therefore, produces gastric acid consistently throughout the day.
One final thing: It’s easy to be a purest as a veterinarian, and I think that common sense amongst horse professionals counts for a lot. I just get worried when we don’t know enough about the supplements we are using, or when owners spend money on supplements that have limited evidence of efficacy.