Ruminant Digestive System

In contrast to an animal with a monogastric digestive system, a ruminant has four stomach compartments and can utilize some feeds more efficiently than a monogastric animal. Ruminants are important to the animal industry because they can use hay and pasture productively.
The Digestive Process

In ruminants, the breakdown of the nutrients in feed into a usable form is very complex. It involves not only the digestive juices and enzymes found in the monogastric system, but the activity of microorganisms found in the stomach. In addition, feed may take one of several paths as it passes through the stomach, depending on the nature of the feed.

In contrast to the monogastric digestive system, the process of digestion does not begin in the mouth in the ruminant, since enzymes are not present in the saliva of ruminants. Instead, digestion begins in the stomach.

Before feeds pass into the omasum and abomasum, they move through either the reticulum or the rumen and reticulum. Three types of microorganisms are present in the rumen and reticulum—bacteria, protozoa, and fungi. These microorganisms help break down feed for digestion. Bacteria have the most important role in digestion. Some bacteria break down the more easily digestible sugars and starches. Other bacteria ferment the fiber found in roughage like hay, grass, and silage to break it down for use by the body. A second type of microorganism, protozoa, also aids the ruminant in digestion by storing sugars and starches, forming some microbial proteins from proteins in the diet, and fermenting fiber. The role of fungi, the final type of microorganism, is not clearly understood, but they play a role in the digestion of fiber. The action of all the microorganism converts sugars, starches and fiber into fatty acids.
Parts of the Ruminant Digestive System

Two common livestock species have a ruminant digestive system. Cattle, both dairy and beef, and sheep are ruminants. The digestive parts and their functions are similar in both species.

Some of the parts of the ruminant digestive system are the same as those of the monogastric digestive system, but other parts are very different. As in the monogastric digestive system, food enters into the system through the mouth and then passes through the esophagus to the stomach. In the ruminant, the stomach is divided into four compartments, called the rumen, reticulum, omasum, and abomasum. Depending on the type of feed, it may pass through all or some of these compartments as it moves through the stomach. When the stomach completes its functions, the feed moves to the small intestine and proceeds through the cecum, colon, and rectum of the large

Functions of the Parts

Each of the parts of the ruminant digestive system aids in the process of extracting the nutrients needed by the animal from feed. Although the parts of the system have some similarities in function to those of the monogastric digestive system, the process of digestion is much more complex due to structure of the stomach.

Mouth – The mouth carries feed into the digestive system. In cattle, the tongue grabs the grass or other feed and brings it into the mouth. The tongue also moves feed to the throat. The cow has front teeth only in the lower jaw, with a dental pad in the upper jaw; when grass is pulled into the mouth, the teeth cut the grass against the dental pad. The mouth also has upper and lower back teeth for chewing cud and other types of feed. Sheep use their lips to bring food into the mouth when grazing.

Stomach – Like the monogastric stomach, the main function of the stomach of the ruminant is to break down feed. Each of the four stomach compartments has its own unique function. Figure 2.2 illustrates the four compartments of the stomach.

Rumen – The rumen, which is also called the paunch, is the largest of the stomach compartments. It helps to break feed down so that it may be digested.

Reticulum – The reticulum is also called the honeycomb because of the texture of the inner wall of the compartment. It pumps roughage back to the mouth through the esophagus for rumination, which is the racing of feed in the form of the cud. The reticulum also works with the rumen in the breakdown of feed.

Omasum – The function of the omasum, or many plies, is not fully understood. However, scientists have found that the omasum absorbs some water and is involved in the absorption of nutrients.

Abomasum – The abomasum is referred to as the true stomach. Its functions are very similar to those of the monogastric stomach. In the abomasum, digestive juices containing acids and enzymes are added to aid in digestion.

Small intestine – In the first portion of the smallintes- tine, called the duodenum, the digestive process started in the stomach continues. Nutrients are absorbed into the bloodstream through the walls of the remainder of the small intestine. Once the nutrients enters the bloodstream, they travel throughout the body to fuel life processes.

Large intestine –The large intestine consists of three parts, the cecum, colon, and rectum. Within the large intestine of the ruminant, the cecum plays a minor role in the further breakdown of roughage. The colon absorbs water and forms undigested wastes into feces, some absorption of nutrients also takes place. The feces are stored in the rectum before being passed out of the body.

Anus – The anus is the opening through which undigestible solid wastes exit from the body. Any portion of the

Summary

A ruminant digestive system like that found in cattle and sheep has many parts that are similar to the monogastric digestive system. However, the stomach of the ruminant has four compartments instead of only one. These com- partments are the rumen, reticulum, omasum, and aboma- sum. The structure of the stomach and microorganisms found in the rumen and reticulum enable the ruminant to digest forage much more efficiently than animals with a monogastric system.