How equine digestive physiology determines welfare requirements, the consequences of management mismatches, and evidence-based nutrition and management strategies.
Equine digestive welfare is determined primarily by the alignment between management practices and the horse's evolutionary physiology. Horses are anatomically and physiologically optimized for continuous consumption of high-fiber, low-starch forage — their relatively small stomach and rapid gastric emptying, continuous acid secretion, and hindgut fermentation system function best with constant forage input and minimal meal-fed starch. Modern management practices that involve twice-daily grain meals, restricted hay access, and prolonged stabling create profound mismatches with this physiology, generating endemic digestive disease: gastric ulcers, hindgut acidosis, colic, and the behavioral dysregulation associated with pain and dietary frustration. The welfare solutions are well-established: ad libitum forage access eliminates gastric acid exposure and promotes natural behavioral expression; reduced or eliminated grain replaces rapidly fermenting starch with slow-release forage energy; and grazing or hay access from the ground maintains natural chewing posture. These interventions align management with physiology rather than attempting to manage the consequences of fundamental mismatches.