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. | Photo: Courtesy Timber Thomson

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