Physiology of the Cecum and Colon
In carnivores the cecum and colon primarily absorb water and some electrolytes to reduce the volume and fluidity of the digesta in the formation of feces. Feces are also stored in the terminal portions of the colon prior to their movement into the rectum for defecation. In omnivores (e.g., pig) and some herbivores (e.g., cattle and sheep) the cecum and colon are also sites of some limited fermentation and
Cecum and colon of the horse
The extremely large and complex cecum and great colon of the horse are primarily sites of fermentation and microbial digestion of complex carbohydrates (cellulose, hemicelluloses). Roughage passes relatively quickly through the stomach and small intestine of the horse, but fermentative digestion and passes through the cecum and great colon may take days. Complex movements of the cecum and the great colon mix the contents to promote fermentative digestion and to expose the contents to the epithelial surface for absorption of short chain fatty acids (SCFA). The pelvic flexure and the junction between the great and small colons (a distinguished reduction in calibre of the intestinal lumen between the great and small colons) are relatively small in diameter, and it appears that the passage of large particles of roughages is restricted. While these sites retain roughage so that it can be subjected to microbial digestion, the potential for impaction at these sites is also increased.