Phenylbutazone—nicknamed “bute”—is one of the most widely used painkillers in horses. It’s cheap, effective, and commonly given for everything from arthritis to post-competition soreness. But there’s a well-known catch: bute can potentially cause gastrointestinal ulceration, and by the time a horse shows obvious signs of stomach or gut trouble, significant damage may already have occurred. This study set out to find early warning signals in the body — measurable proteins that could flag the problem before it gets serious.
The researchers used a cutting-edge technique called proteomics, which is essentially a large-scale scan of all the proteins present in a biological sample. They compared protein expression in the blood and feces of seven horses treated with a standard clinical dose of bute (4.4 mg/kg) against seven horses given a placebo. Think of it like running a detailed ingredient check on the body’s chemistry before and after the drug — looking for anything that changed in meaningful ways.
The results were striking in scope. The analysis identified over 5,000 proteins in blood and over 3,500 in fecal samples, ultimately finding 226 significant proteins in blood and 181 in fecal samples that were notably different between the bute-treated and control groups.
One protein stood out from the crowd: fatty acid-binding protein 6 (FABP6). This protein, found in the intestinal lining, is normally involved in absorbing fats, but it leaks into the bloodstream and stool when the gut wall is damaged. The researchers validated FABP6 as a potential biomarker using a standard lab test called an ELISA — an important step toward making any future diagnostic test practical and affordable for veterinary clinics.
Why does this matter for horse owners? Early detection of bute-induced gut injury would be useful for the diagnosis, treatment, and prevention of bute toxicity. Right now, vets often have to rely on scoping the stomach or watching for clinical deterioration. A simple blood or fecal test that could catch gut damage in its earliest stages would allow vets to intervene sooner — adjusting doses, switching medications, or adding gut-protecting treatments before a horse ends up seriously ill.
While more research is needed to confirm FABP6’s usefulness across larger and more diverse horse populations, this study opens a promising door toward safer, smarter use of one of equine medicine’s most essential drugs.
Peer-Reviewed Paper Title: The proteomic differences and expression of fatty acid-binding protein 6 (FABP6) associated with gastrointestinal injury in horses with oral administration of a clinical dose of phenylbutazone.
Authors: Ruethaiwan Vinijkumthorn, Nawarus Prapaiwan, Thanapon Chotikaprakal, Phirom Prompiram, Narumon Phaonakrop, Sittiruk Roytrakul, Parichart Tesena.
Affiliation: This research project was funded by Mahidol University (Fundamental Fund: fiscal year 2024 by National Science Research and Innovation Fund (NSRF).
Further Reading: Vinijkumthorn R, Prapaiwan N, Chotikaprakal T, Prompiram P, Phaonakrop N, Roytrakul S, et al. The proteomic differences and expression of fatty acid-binding protein 6 (FABP6) associated with gastrointestinal injury in horses with oral administration of a clinical dose of phenylbutazone. Equine Vet J. 2026;58(3):845–856. https://doi.org/10.1111/evj.14538
