Digestive System of Ruminants Explained

What You Should Know About Cattle Nutrition of Ruminants


A cow busy ruminating fresh grass

Laying cow, busy ruminating

Cattle (along with sheep, goats, and their wild cousins like water buffalo) have the most complicated digestive systems found in the animal kingdom.  The complexity of the bovine digestive system, however, also provides the great advantage of versatility, allowing it to digest even the most fibrous food.

Unlike most animals that have a basic stomach with one compartment, cattle have a more complex stomach separated into four distinct chambers.  (A cow having multiple stomachs is actually a misnomer – it is one stomach with four chambers.)  Animals that have a stomach with compartments capable of digesting the high amount of cellulose found in very fibrous forage are known as ruminants.  The term ruminant is related to the second chewing of large pieces of forage that return to the mouth from the stomach – known as chewing the cud.  While most animals secret acids and enzymes into the stomach for digestion, ruminants use a very unique fermentation process to break down food into useful nutrients.

Proper nutrition and feed management starting from the birth of a calf is important to developing the proper types and levels of micro-organisms that aid the ruminant fermentation and digestive process.  Let’s review how the ruminant’s digestive process works and how to keep it healthy, starting with the cow’s stomach.

The Unique Cow Stomach

As noted above, cows have one stomach divided into four separate chambers or compartments listed below:

  • Reticulum
  • Rumen
  • Omasum
  • Abomasum

These four compartments work in a coordinated way to break down highly fibrous forage in order to release the sugars and proteins contained in the plant’s densely walled cells.

The reticulum and the rumen, the first two chambers, are very connected and are continually exchanging contents, to the degree that they are commonly referred to together as the reticulo-rumen.  The rumen, which is by far the largest stomach section in mature cattle, is where the fermentation takes place, and where an important mixture of bacteria, fungi, and other micro-organisms aid the slow, two to four days fermentation process.  The contents of the reticulum continually mix with the contents in the rumen.  In the reticulum, the contents are sorted with the largest pieces returned to the mouth for additional chewing and the smallest pieces sent to the next chamber, the omasum, for the next stage of digestion.  The rest remain in the rumen for further fermentation.

The omasum contains many folds that effectively absorb liquids, which it passes on to the blood stream.  The last compartment, the abomasum, is similar to the stomachs found in most animals.  It uses acids and enzymes to further break down the particles so that they can be absorbed into the blood stream.  It also breaks down proteins and other by-products of the fermentation process.

The remainder of the digestive tract is also similar to other animals.  The small intestine continues the digestive process using a new set of enzymes secreted by the liver and pancreas – breaking down fat and proteins and absorbing them into the bloodstream.  The large intestine absorbs remaining liquids and forms the feces.

Calf Digestive Development

Calves are not naturally born with the ability to properly ferment fibrous forage in its stomach.  It must develop that ability by nutritionally consuming feed that aids in suitable fermentation.  In fact, in the first few months of life, calves could technically be considered non-ruminants.  In calves the rumen is not the largest stomach compartment; a calf must develop a mature rumen.

During the early nursing stage, the rumen basically acts like a part of the esophagus, passing the protein heavy milk onto the later stomach chambers.  Only when the calf starts to eat forage after a few weeks does the rumen start to develop.  Therefore, providing forage during this crucial stage is critical to rumen development.  A calf unable to develop a proper rumen and fermentation process at the appropriate age may develop serious digestive tract conditions, and will likely experience delayed growth.

Besides creating the proper chemical contents in the rumen for fermentation, eating forage also develops the muscular lining in the rumen necessary for proper absorption.

Water is also critical at this early stage of rumen development.  Without water, the bacteria and other micro-organisms needed for fermentation will not grow properly.  Milk or other liquid feed do not aid in rumen development as it bypasses the rumen.  Only water will aid in the rumen development.

Common Cattle Digestive Problems

With a complex stomach to digest highly fibrous forage, things can go wrong.  As discussed above, for calves, not having access to forage and water will delay rumen development possibly resulting in scours or other digestive problems.

Other common digesting issues include:

Bloat -Excessive gasses in the rumen can be caused by consuming too much legumes/grain or too much fresh grasses.  The cattle digestive system relies on regular fibrous forage to maintain its chemical balance.

Acidosis- The chemical balance that aids fermentation in the rumen is very much determined by the diet of the cow.  A sudden change in diet, for example from mostly hay to mostly grain, can result in a rapid increase in acidity in the rumen.  Acidosis can damage the lining of the rumen causing digestive disruption and dehydration.

Maintaining Healthy Cattle Digestion

The best way to aid a calf or a herd maintain a healthy digestive system be sure to do the following:

1) Help a calf properly develop its rumen and rumen fermentation by regularly providing adequate forage and clean water when it is a few days old.
2) If feeding the herd legumes and grains, maintain a proper and regular balance of forage in the diet.
3) Feed the herd hay before setting it out in fresh green pastures to avoid cows bingeing on the fresh grass.

A healthy digestive system means your herd and your calves will also likely remain healthy.  When problems occur, than cattle may not maintain proper nutrition making them more prone to disease and illness. Now that you understand that a healthy digestive system is important, you need to see this information to learn more about getting healthy calves.

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