Normal equine gastroduodenal secretion and motility

This article represents an attempt to provide an overview of the current knowledge of equine gastroduodenal secretory and motor activity, with respect to how these functions are controlled and interact. First, the equine gastric mucosal anatomy is discussed in comparison with other monogastric species, with some attention directed at the large nonglandular portion in relation to its function, or lack thereof. Next, control of gastric acid secretion, as assessed by the collection of gastric contents from a cannula or continuous measurement of their changes in pH, is reviewed, pointing out that there appears to be a relatively unobstructed movement of contents between stomach and duodenum in the horse, which can have a strong influence on pH of the gastric contents in particular. Then, methods of evaluating gastroduodenal motility, including recording of myoelectrical activity and changes in intraluminal pressure, and transit of radiolabelled contents from stomach into duodenum, are discussed. Finally, the apparent influence of the gastroduodenal migrating motility complex (MMC) on the composition of fasting gastric contents is introduced to underscore the observation that reflux of duodenal contents into the stomach is probably a common occurrence in the horse, particularly during periods of MMC-related cessation of antral motility.