Performance horses have a special set of needs that set them apart from other horses. Not only do they have greater physical demands being placed on them but they are also exposed to a large number of stressors.
Stress can cause pH fluctuations in the gut of a horse as more acid is produced and pushed up into the first portion of the stomach. Repeated exposing the stomach lining to this high level of acidity can, over time, cause ulcers. In general, it creates discomfort that can result in a loss of focus and performance. Neutralizing stomach acid before any potentially stressful event (hauling, performing, practice) can keep ulcers at bay and guard against the loss of beneficial gut flora.