A Citrus Oil Supplement Might Have a Calming Effect on Horses

Horse owners often administer calming supplements to their mounts for a variety of safety and welfare reasons, from navigating stressful situations to keeping horses safe on stall rest. Many of these products’ efficacy, however, has been tested primarily in mice and humans, not horses, said Timber Thomson.

So Thomson, a graduate student working with Jessica Suagee-Bedore, PhD, in the Department of Agricultural Sciences at Sam Houston State University, in Huntsville, Texas, tested one calming supplement’s effects on young horses in training. She presented her findings at the 2019 Equine Science Society Symposium, held June 3-6 in Asheville, North Carolina.

Specifically, Thomson evaluated a calming supplement (Equinutrix’s ZENRG) containing citrus oil, magnesium, and yeast. In her study she compared seven young horses that received the supplement with seven young horses that did not (the controls). All horses were in a four-day-a-week training program throughout the two-month study period. The treatment group received the supplement top-dressed on their feed once a day at the manufacturer’s recommended dose. To test the product’s efficacy, she had each horse perform an anxiety test, a trailering test, and a startle test.

During the anxiety test Thomson placed each study horse in a large pen beside a grain bucket and placed a companion horse in a round pen at the other end of the enclosure. She calculated how much time the horse spent next to the companion (a sign of anxiety) vs. at the grain bucket.

During the trailer test Thomson monitored the horses’ behavior and heart rates (using Kentucky Equine Research’s Clock-It app) during a 15-minute trailer ride.

With the startle test, she measured horses’ exit speed and distance traveled when startled from behind and released from a chute. This latter experiment was the only one that produced statistically significant results. Thomson found that the supplemented horses had a reduced reaction velocity following the startle test, as measured by the number of seconds they took to move 10 feet.

“It is possible that this novel blend reduces startle response in young horses,” she said. “This could have positive benefits for human safety during the training process and for horses with high startle responses, but future research is needed.”