Ruminant animals have a four-chambered stomach that allows them to digest plant fibers through microbial fermentation. Food is initially chewed and swallowed, passing to the rumen and reticulum where microbes break down cellulose and other plant matter. Nutrients are absorbed and the remaining cud is regurgitated and rechewed before passing to the omasum and abomasum for further digestion and absorption. This unique digestive system relies on microbes in the rumen to break down plant fibers that the animal cannot digest on its own, extracting nutrients that the ruminant then absorbs in the lower stomach and intestines.

1. Digestion in
ruminants
Submitted By:- Gurleen bhinder
(L-2018-BS-235-M)
Submitted To:- DR. NEENA CHAWLA
Course No:- BIOCHEM 509
Course Title:- ANIMAL BIOCHEMISTRY

2. Definition - What
does Ruminant
Animals mean?
Ruminant animals are animals that chew and regurgitate
their food more than once, and digest it multiple times in
different stomachs. These animals are quadruped mammals
with even toes, hooves and chew the cud. They generally
have four stomachs with different characteristics, which are
used at different stages in digestion. These animals include
cattle, sheep, buffalo, antelopes, giraffe, and camels.

3. 5% of the
population of domesticated ruminants constitute
species: cattle, sheep and goats
9

4. Pathway of food through
digestive system:-
 Mouth
 Esophagus
 Rumen
 Reticulum
 Back to mouth for chewing of cud
 Omasum
 Abomasum
 Small Intestine
 Large Intestine

5. The digestion process
in Ruminants begins
by chewing its food
in mouth. Ruminants
do not completely
chew the food they
eat, but just consume
or gulp as much they
can

6. After the food is
broken down into
smaller particles it is
swallowed and passes
through the esophagus
using muscle
contractions known as
peristalsis

7. The stomach of these Ruminants is divided
into 4 chambers:-
1. Rumen,
2. Reticulum,
3. Omasum
4. Abomasum.

8. The process of digestion begins with the first two chambers of the
stomach, the rumen and reticulum by softening the ingested
matter. Later the microbes present in the rumen produces the
cellulase enzyme required to digest the cellulose.
An important characteristic of ruminants digestive
system is the occurrence of the microbial fermentation prior to the
gastric and intestinal
digestion activity.
Rumen has a complex environment composed of microbes.
Rumen microorganisms usually adhere to feed particles
and form biofilms to degrades plant material.
These animals have highly diversified rumen microbial
ecosystem consisting of bacteria, ciliate protozoa, anaerobic fungi
and bacteriophages

9. The feedstuffs consumed by ruminants are all initially
exposed to the fermentative activity in the rumen, the
place of more or less complete microbial fermentation
of dietary components.
Ruminal fermentation initially results in the degradation
of carbohydrates and protein to short-term intermediates
such as sugars and amino acids.
The products of this initial degradation are readily
metabolized to microbial mass and carbon dioxide,
methane, ammonia and volatile fatty acids (VFA):
primarily acetate, propionate and butyrate and to a
lesser degree branched chain VFA and occasionally
lactate

10. Once the plant fibers have been broken down to
provide vitamins, proteins, and other organic
acids, the nutrients are absorbed into the
animal’s bloodstream.
Coarse plants are sent further into the next
chamber for further digestion. Here is where the
further bacterial action takes place and the food
is formed into soft chunks called the cud.
This cud produced is regurgitated back into the
animal’s mouth where they can be chewed again
The saliva of the cow greatly aids in digesting the cud. After chewing, the food
bypasses the two chambers of the stomach and directly enters the third chamber.
The walls of the third chamber mash and compact the food molecules further, and
then pass it to the fourth chamber – the abomasum. The final digestion in the
stomach is carried by the abomasum and then passed to the intestine.

14. The Ruminant Digestive System
Small Animal Nutrition TM 14
Esophagus
Rumen
Reticulum
Omasum
Abomasum
Small
intestineCecum
Colon
Rectum

15. The Non-Ruminant Digestive System
Small Animal Nutrition TM 15
Esophagus
Stomach
Small
intestine
Cecum
Colon
Rectum

16. Vertebrates lack the ability to hydrolyse the beta [1–4] glycosidic
bond of plant cellulose due to the lack of the enzyme cellulase.
Thus, ruminants must completely depend on the microbial flora,
present in the rumen or hindgut, to digest cellulose. Digestion of
food in the rumen is primarily carried out by the rumen microflora,
which contains dense populations of several species of bacteria,
protozoa, sometimes yeasts and other fungi – 1 ml of rumen is
estimated to contain 10–50 billion bacteria and 1 million protozoa,
as well as several yeasts and fungi.
Since the environment inside a rumen is anaerobic, most of these
microbial species are obligate and facultative anaerobes that can
decompose complex plant material, such as cellulose,
hemicellulose, starch and proteins. The hydrolysis of cellulose
results in sugars, which are further fermented to acetate, lactate,
propionate, butyrate, carbon dioxide, and methane.

17. As bacteria conduct fermentation in the rumen, they consume about
10% of the carbon, 60% of the phosphorus, and 80% of the
nitrogen that the ruminant ingests. To reclaim these nutrients, the
ruminant then digests the bacteria in the abomasum. The enzyme
lysozyme has adapted to facilitate digestion of bacteria in the
ruminant abomasum. Pancreatic ribonuclease also degrades
bacterial RNA in the ruminant small intestine as a source of
nitrogen.
During grazing, ruminants produce large amounts of saliva –
estimates range from 100 to 150 litres of saliva per day for a cow.
The role of saliva is to provide ample fluid for rumen fermentation
and to act as a buffering agent. Rumen fermentation produces large
amounts of organic acids, thus maintaining the appropriate pH of
rumen fluids is a critical factor in rumen fermentation. After digesta
pass through the rumen, the omasum absorbs excess fluid so that

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