Timber Thomson, a graduate student at Sam Houston State University, evaluated a calming supplement 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 effect, she had each horse perform an anxiety test, a trailering test, and a startle test.