Antibiotic Use and Gastric Ulcers in Horses

Horses on antibiotics might experience feeding, housing, and management changes as well as increased stress, which are associated with gastric ulcer development.

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While there is no published evidence to support the association between antibiotic administration and gastric ulcers, changes in management during antibiotic treatment could put your horse at risk for ulcer development. | Adam Spradling/The Horse

Q: My pleasure horse is currently on antibiotics due to a wound he sustained in the pasture. Do I need to be concerned about him developing gastric ulcers from being on this course of antibiotics? What, if anything, can I do to combat the development of ulcers?

A: The judicial use of systemic antibiotic administration is often a critical component of successfully treating bacterial infections in horses. Along with the substantial benefits however, there are also potential adverse effects of antibiotic therapy. Diarrhea/colitis are likely the most common of these side effects, but kidney, liver, and neurologic effects, along with several other rare reactions, may be encountered. Conversely, there is no published evidence that administration of antibiotics in horses is associated with development of equine gastric ulcer syndrome (EGUS) in either form, equine squamous gastric disease, or equine glandular gastric disease. When administering antibiotics to horses, always follow your veterinarians’ instructions to minimize the risk of adverse effects.

Consideration of EGUS development in this situation is important. A horse being treated for a wound may experience feeding, housing, and management changes as well as increased stress, all of which are known factors associated with the development of EGUS. Combating the development of ulcers is closely tied to two things—managing how we feed our horses and alleviating stress in our horses’ lives.

In their natural state horses graze the majority of the day, producing large amounts of saliva and taking in enough grass to help protect the upper, acid-sensitive portion of the stomach from acid. Because a horse’s stomach produces acidic gastric fluid continuously, and in quantities of up to 16 gallons per day, the salivary buffering and physical protection is important to maintaining a healthy digestive system. When we practice episodic feeding with “dried” roughage and/or concentrated feeds, we interrupt the natural ability of the horse to buffer acid in the upper portion of the stomach. Providing access to grazing, hay in slow feeder nets or bins, and feeding small concentrate meals throughout the day are recommendations to decrease ulcer development risks.

Another way to help prevent ulcers is to reduce stress as much as possible. Many horse owners think it’s only the big events, like showing, trailering, or moving to a new barn that can trigger stress, but that’s not the case. Even what we might consider small things, such as storms, changes in feeding times, moving to a different pasture, or changing a turnout buddy, can also lead to stress, which can lead to the development of ulcers. Sticking to a routine as much as possible with our horses’ work, training, feeding, and turnout schedules can help. Horse owners can also download Relax Trax, a music soundtrack developed by an animal sound behaviorist specifically for horses. It’s available for free here. Consult your veterinarian if you think an approved gastric ulcer prevention could be beneficial to your horse’s circumstance.


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Written by:

Hoyt Cheramie, DVM, MS, Dipl. ACVS, is a member of the the Boehringer Ingelheim Professional Services Veterinarian Team. He has expertise in performance horse medicine and has teaching experience at the Virginia-Maryland Regional College of Veterinary Medicine. He has practiced in Kentucky, Louisiana, Georgia, and Illinois. He earned his doctor of veterinary medicine from Louisiana State University School of Veterinary Medicine.

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