Rumination in Animals
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Rumination in Animals

Rumination is the peculiar process of digestion observed in the Ruminant class of mammals. Rumination helps the animals to extract maximum possible nutrients from the plant materials.

Ruminants are a class of herbivorous mammals. They are named so as they regurgitate the partially digested food from their stomach, which is known as Cud, and chew it again. Rumination, the process of rechewing the cud, facilitates the proper breakdown of the cellulose rich plant matter. Ruminants are even toed, hoofed mammals, which consume food in bulk and digest later. Goat, sheep, camel, cow, giraffe etc. are some distinguished ruminants.

The major feature of ruminant mammals is their chambered stomach. While most of the ruminants have four chambered stomachs, camels have only three chambers. Each of these chambers houses numerous symbiotic organisms that play a major role in the host’s digestion cycle. The symbiotic organisms are mainly bacteria, fungi, protozoa and viruses.

The ruminant stomach facilitates microbial digestion of plant matter. The symbiotic organisms/microbes are chiefly starch fermenters and cellulose fermenters. They produce cellulase enzyme. The cellulase enzyme breaks down the cell walls of the plant matter to release fatty acids. Non-ruminants cannot digest plant matter owing to the absence of cellulase enzymes. Around 60%-75% of the ingested matter is fermented by microbes before being exposed to the gastric enzymes in the abomasum.

The ruminant stomach has four distinct chambers:

  1. Rumen
  2. Reticulum
  3. Omasum
  4. Abomasum

The rumen is the site of methane production in ruminants. It is estimated that 20% of global methane production is attributed to ruminants. Methane is a major greenhouse gas and contributes towards global temperature rise.

The abomasum is the true stomach and is similar to the human stomach on the basis of the tissue structure.


Process of Digestion

Ruminants have a peculiar digestive cycle. Food enters the rumen and gets partially digested. The fluid content of the food gets collected in the reticulum and the solid portion gets collected in the rumen. This partially digested food is then clumped into small balls called bolus and regurgitated into the oral cavity. The bolus gets mixed with saliva and gets further broken down. This is now passed into the next chamber, which is the omasum. Water and minerals are absorbed into the blood stream in the omasum. The partially digested food then moves into the abomasum, which is the true stomach. The walls of the abomasum secrete digestive enzymes. The process of digestion that takes place here is equivalent to the digestion that takes place in humans. Acid hydrolysis of microbial and dietary protein takes place here and the protein sources are further processed for digestion and absorption in the intestines. The digested food finally leaves the stomach and enters the intestines where the nutrients are absorbed into the blood stream.


Rumination in Humans

Though human beings are non-ruminants, rumination can occur under certain circumstances. Rumination syndrome is an eating disorder in humans, where there is voluntary or involuntary regurgitation of partially digested food. Individuals diagnosed with bulimia nervosa in the past are more susceptible to this syndrome. However, unlike the ruminant animals, rumination in humans is considered as a health disorder rather than a physiological function.

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Comments (1)
Ranked #20 in Biology

I keep sheep people often wonder about why they stand and chew, I wrote an article on why animals chew their cud just a few weeks ago.