Pro Earth Animal Health Zesterra®What is Zesterra? Zesterra is an all natural supplement designed to support horses during times of stress, such as hauling, heavy training, foaling and during times of extreme heat or cold. Zesterra is safe for all classes of horses including lactating mares and foals. Zesterra stimulates appetite and water consumption safely and naturally by balancing the pH of the stomach. It can be used as a flavor enhancer for horses that reject water from new