The FEI has warned riders to be vigilant over feed supplies following a spate of positive tests for the banned substance synephrine.
Ten horses have tested positive for the stimulant this year, the majority based in South America. This includes four cases at the CSI4* in Balvanera, Mexico (2 to 5 March).
The FEI said investigations into the source of the positives was ongoing but that it wanted to “warn stakeholders” about the substance and “advise on measures that can be taken to prevent a positive finding”.
Synephrine is classified as a specified substance on the equine prohibited substance list, which acknowledges the risk of it accidentally entering a horse’s system through environmental sources.
Synephrine — which is used as a weight loss aid and can cause vasoconstriction and an increased heart rate — is found in plants in certain regions of the world.
It has been detected in teff grass hay in some countries, as well as in the common rush (juncus usitatus), mullumbimby couch (Cyperus brevifolus) and the leaves of citrus trees (such as mandarin, orange and lemon).
The FEI warned the substance can also be present as an ingredient in herbal and nutritional supplements and is commonly found in the peel extract of bitter orange (also known as Seville orange), which is used as a flavouring agent.
Horse & Hound Newsletter
Never miss out on the latest happenings in the equestrian world
“The FEI urges stakeholders to be vigilant of possible sources of synephrine in the horse’s environment and implement management practices to prevent contamination or inadvertent ingestion of the substance,” a statement from the FEI said.
The organisation suggested riders use “reputable suppliers of hay, feed and supplements,” as well as “checking the horse’s environment for plants containing synephrine” and ensuring that “any personnel taking supplements or other products containing synephrine wash their hands thoroughly after coming into contact with the substance”.
“Additionally, it is recommended that samples are kept of batches of hay, feed and supplements given to competition horses to enable a thorough investigation to take place should the horse test positive for synephrine,” the statement said.
For all the latest news analysis, competition reports, interviews, features and much more, don’t miss Horse & Hound magazine, on sale every Thursday.
Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now
