Mean glandular severity scores were significantly lower in the treatment group on Days 28 (shown) and 35, as seen on gastroscopy exam. | Courtesy Dr. Frank Andrews

Equine gastric ulcer syndrome (EGUS) refers to any ulceration inside a horse’s stomach. It often causes severe physical pain, leading to clinical signs such as behavior changes, weight loss, and loss of appetite.

Veterinarians view omeprazole as the mainstay EGUS treatment, said Frank Andrews, DVM, MS, Dipl. ACVIM, LVMA equine committee professor of equine medicine and director of equine health and sports performance at Louisiana State University’s School of Veterinary Medicine, in Baton Rouge. He spoke on the subject at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida. But because omeprazole might not be suited for long-term use, he said he and his team studied a schizophyllan—a beta-glucan—and hyaluronan product (relyneGI) to see if it could be useful in caring for ulcery horses.

Schizophyllan and Hyaluronan

Hyaluronan is a high-molecular-weight glycosaminoglycan in joint, intestinal, and gastric tissues. “It functions to maintain gastric and intestinal homeostasis, innate immunity, and modulates inflammation,” said Andrews. “In rats—which have a similar stomach to a horse with a squamous and glandular region—hyaluronan has been proven to protect the gastric lining and improve gastric mucosa integrity.”

Beta-glucans are an integral part of cell walls; schizophyllan activates immune cell maturation, differentiation, and proliferation. They have prebiotic properties and have been proven safe for use in horses.

Andrews and his team studied the efficacy of the new schizophyllan and hyaluronan gastric support supplement in 12 stall-confined Thoroughbred and Thoroughbred-cross horses with naturally occurring gastric ulcers. They divided horses evenly into treatment and control groups, performed gastroscopic exams, and weighed each horse at the start of the study after two days of acclimatization.

Over the 35-day treatment period the team gave 1 ounce (the high-stress dose) of the supplement three times daily in each treatment group horse’s feed and a 1-ounce dose of placebo three times daily in each control horse’s feed. They were blinded to treatments to avoid bias in scoring and repeated gastroscopies and weight checks on Days 14, 28, and 35.

Supplement Effects on Gastric Ulcer Scores

Andrews and his team saw a significant weight increase in all horses, but the treatment did not affect body weight. The mean nonglandular EGUS and severity scores were significantly lower in the treatment group on Days 28 and 35.

“The nonglandular ulcers were healed, except for mild hyperkeratosis (callousing), on these dates as well,” Andrews said. “The mean glandular (ulcer) and severity scores were significantly lower after 14 days in the treatment group. The ulcers did heal, but some reoccurred in both groups of horses by Day 28, which is not uncommon in these types of ulcers.” The mean gastric fluid pH remained low and variable throughout the study in both groups. Many drugs when used long term block gastric acid, which can change the stomach’s physiology. In other words, this supplement contributed to gastric health without changing stomach acidity.

Take-Home Message

Based on the research, Andrews said he believes the schizophyllan and hyaluronan supplement might have uses for managing horses with EGUS long-term and/or in conjunction with appropriate pharmaceutical treatment. (Supplements shouldn’t be used to treat disease but improve stomach health after discontinuing pharmacologic agents, he added.) The researchers observed clear improvement in nonglandular and glandular ulcer scores in the treatment group and did not observe any adverse effects from the supplement. The horses also readily consumed it, he added.

Andrews noted study limitations were a small sample size with limited breeds, a short treatment period, and that horses were stalled without exercise—management approaches that can be risk factors for ulcers. He hopes to address these limitations in future studies by finding out if the schizophyllan and hyaluronan product acts synergistically (a combined positive effect) with omeprazole or other drugs to improve gastric health in horses as well as prevent gastric ulcer recurrence.