Purina® Outlast® Gastric Support Supplement is formulated to support gastric health and proper pH. It is estimated that up to 90 percent of active horses experience gastric discomfort, a?ffecting health, attitude and performance. Common activities including stall confinement, exercise, transportation, weaning and few environments such as events and shows are known to cause stress and gastric discomfort. Purina® Outlast® Gastric Support Supplement was developed by our Ph.D. Equine Nutritionists to support a healthy gastric environment.