Topic #3045 Digestion/Absorption
By: Alisa Kowalski
Ruminant
• An animal with 4 distinct compartments in
its stomach, which swallows its food
essentially unchewed, regurgitates it, chews
it thoroughly and reswallows it.
• Examples: cattle, sheep, goats, deer, and elk
Nonruminants (Monogastrics)
• An animal having a single compartment in
its stomach, which swallows its food after
chewing and does not regurgitate it.
• Examples: pigs, humans, bears, and dogs
Ruminant Stomachs
• The four compartments are
– Reticulum - honeycomb -5%
– Rumen - paunch -80%
– Omausm - manypiles -7%
– Abomasum - true stomach -8%
Reticulum
• Nickname - “hardware stomach”
• Furnishes additional storage space
• Holds foreign material to prevent damage to
other internal organs
– Examples: nails and wire
• A magnet may be fed to ruminants to catch and
hold this foreign materials in the reticulum
Rumen
• Largest compartment
– Capacity of 40-60 gallons in mature cattle
• Serves as a storage area
• Does not develop in young until solid food
is ingested by the animal
Bacterial Action in Rumen I
• Reason why ruminants can digest large
quantities and live on a much lower protein
diet than monogastrics.
• As the bacteria multiply they make protein
to construct their own bodies call bacterial
protein.
Bacterial Action in Rumen II
• The bacterial protein is digested later in the
stomach (abomasum) and the intestines of
the ruminant
• Ruminants are able to consume a lower
quantity and quality of dietary protein.
• The bacteria make up for it by multiplying
and making protein from non-protein
sources.
Omasum
• Muscular section that squeezes the water
from the feed before it enter the abomasum
Abomasum
• “True stomach”
• Digestive juices containing enzymes cause
chemicals changes to break down the proteins,
carbohydrates, and fats into simpler substances
which can pass into the small intestine for
further digestion and absorption into the blood
stream.
Regurgitation
• During the process of eating ruminants
chew their feed just enough to make
swallowing possible.
• After ruminants have consumed their feed, a
bolus (food ball) is brought up form the
rumen and chewing is completed.
– Chewing their cud
Non-Ruminant Digestion
• Food is swallowed directly into the single
compartment stomach, where it is mixed
with the digestive juices.
– Contains enzymes to break down foodstuffs
• Very little bacterial action
• No conversion of low quality protein to
high quality protein
Non-Ruminant Digestion
• Monogastrics are unable to digest large
quantities of fiber unless they have an
enlarged cecum
• Animals with an enlarged cecum
– Sometimes called pseudo ruminants
– Examples: horses, rabbits, and guinea pigs
Non-Ruminant Digestion- Cecum
• Blind pouch at the first portion of the large
intestine.
• Main place for bacterial breakdown in
horses and rabbits
Digestion & Absorption by Livestock
• Digestion- the process by which large,
complex food molecules are broken down
into simpler molecules within the digestion
system to prepare them for absorption and
use by the body
Digestion & Absorption by
Livestock - Enzymes
• Organic compounds which bring about
changes in other organic compounds
without themselves being changed or
broken down.
• Break down complex feeds into simpler
forms through chemical reactions
Importance of Chewing
• Chewing- physical process of breaking
down foodstuffs to smaller particles.
• Increasing of surface area allow greater area
for enzymatic activity
Digestion of Carbohydrates
• Must be broken down into simple starches
and sugars before they can be absorbed in
the small intestine.
• Begins in the mouth in animals whose saliva
contains the enzyme ptyalin (non-ruminants).
– Begins in rumen in animals without ptyalin
• The rest is digested and absorbed in the
small intestine.
Bacterial Digestion of
Carbohydrates
• Millions of bacteria and protozoa grow in the
mass of water and feed in the rumen.
– Secrete enzymes which digest the carbohydrates
and proteins
– Reproduce and grow using the digested material,
primarily the protein
Bacterial Digestion of
Carbohydrates
• During this process they also synthesize B
vitamins
– Used in the nervous system & to release energy
from digested nutrients in the host animal
• Because of this adult ruminants do not need
dietary B vitamins
Bacterial Digestion of
Carbohydrates
• Small amount of the digested cellulose and
other carbohydrates is incorporated into the
rumen “organisms”
• Most is converted into organic acids
– Volatile Fatty Acids (VFAs)
– Acetic, propionic and butyric
– Absorbed directly through the rumen wall into
the capillaries of the circulatory system.
Bacterial Digestion of
Carbohydrates
• Similar activities occur in the cecum of the
horse and rabbit
– Horses have little need for B vitamins due to this
• Relationship between the rumen protozoa &
bacteria and the host (or ruminant) is called
SYMBIOSIS.
• Way in which two organisms of two different
species live in intimate association with each
other
Relationships Between Organisms
• Mutualism - each helps the other
– Example: man and dairy cow
• Commensalism - one benefits, the other does not
– Example: Sheep tick on a sheep
• Parasitism - one depends on the other for some
essential food factor, often detriment to host
– Example: leech on fish
• Phoresis - the host transports the symbiont
– Example: barnacle on a whale
Protein Digestion
• Broken down into peptides (smaller units) and
amino acids (building blocks of proteins) in
the stomach or abomasum of ruminants
• Begins in stomach with pepsin
– Enzyme found in the gastric juices
• Final digestion in the small intestine where
absorption also occurs
Fat Digestion
• Do not undergo digestion until they reach
the small intestine
• Bile and enzymes from the pancreas help in
the breakdown of fats so they can be
absorbed in the small intestine.
Villi
• Line the intestines and are minute finger-like
projections or papillae
• Provide a larger surface are in the lining of
the intestine so there is more surface area for
absorption of nutrients
Distribution of Nutrients
• Most nutrients are absorbed by the villi in
the small intestine and enter the circulatory
system
• The blood, containing these nutrients,
reaches the capillaries in all the body tissues
• Here the nutrients pass through the capillary
wall into the lymph (clear fluid occupying
the space between the cells).
Distribution of Nutrients
• The nutrients then enter the cells, providing
nourishment and energy for the various life
processes