Functions of Various Parts of Digestive Tract: Large Intestine

The large intestine is the terminal part of the alimentary canal; it consists of the caecum (blind sac), colon, and rectum. The size of the large intestine varies considerably in farm animals. In horses it constitutes 46% of the total volume of the digestive tract. In ruminants, it represents only 10% of the total digestive tract capacity. The large intestine serves as a major site for the absorption of water, sodium, and chloride. Other salts such as potassium, phosphorus, and magnesium can also be absorbed from the large intestine. The large intestine has only mucous secretions and no enzymatic activity.
Undigested materials which escape the digestive processes in the stomach and small intestine are subjected to microbial digestion in the caecum. In monogastric animals, particularly horses and rabbits, the caecum serves as a major site for digestion of fibrous materials. This is accompanied by a variety of microflora. However, microbial digestion and absorption of end products in the caecum is not as efficient as it is in the rumen, and therefore does not nutritionally benefit the animal as much. The microbial protein synthesized in the caecum is mostly excreted in the faeces. The colon is part of the large intestine extending from caecum to rectum. The rectum is a dilatable tube serving as a storage place for feces until it is excreted.
The anus is the opening at the posterior end of the alimentary canal under the root of the animal's tail. The anal canal or lumen is normally closed by the contraction of sphincter muscles. During defecation, this canal is opened and undigested material (excreta) is passed through the anus.
Note: Next post on this blog will cover, "Practical Implications of Comparative Digestion in Farm Animals"