Animal Digestive Systems
Topic # 3024
Ms. Blakeley
http://www.glenroseffa.org
Digestive System – Objectives



Describe and understand the basic functions of
the primary components of the digestive system.
Compare the functions and locations of the
digestive organs in man, poultry, horses, cows
and swine.
Differentiate between and identify digestive
systems of man, horses, swine, poultry and
cows.
Digestive System


Where large complex molecules are broken down
into simpler molecules
Digestive Tract:
– Long tube beginning with mouth and ending with the anus

Polygastric (Ruminant)
– A stomach with more than one compartment
• (cows, sheep, deer)

Monogastric (Non-ruminant)
– A stomach with one compartment
• (swine, horses)

Avian (Poultry)
– No true stomach
• (chickens, geese)
Digestive Systems




Man & Pig have a simple stomach with an
extensive intestinal system
Horses & Rabbits have a simple stomach with
an extensive intestinal system and an
enlarged caecum
Ruminants have a complex stomach with a
simpler intestinal system
Poultry have no teeth and no true stomach
with a crop and gizzard to grind food
Mouth & Esophagus

Mouth: “prehensile” tool (grasps & mixes food)
– Chewing breaks down food
– Salivary Glands secrete juices containing enzymes
(digest food)
– Mucin lubricates the feed for swallowing

Esophagus: muscular tube that connects mouth
to stomach
– Peristaltic waves send feed down the esophagus,
(muscle contractions).
– Reverse Peristalsis = blowing chunks
– The cardia, located at the end of the esophagus
prevents feed in the stomach from coming back into
the esophagus. ( non-ruminants only)
Simple Stomach


Muscular organ, receives feed
Gastric juices are secreted by the glands in
the stomach wall
– start when masticated feed enters the stomach
– Gastric juices have about 0.2 to 0.5 percent HCl

The wall of the stomach is lined with muscle,
this muscle churns and squeezes the feed
– This action forces the liquid portion on into the
small intestine
Ruminant Stomach


Occupies 3/4 of abdominal cavity, mostly
on the left side
Rumen (paunch): 80% of stomach, lighter
food collects here
– Microbes digest cellulose
– Uses lots of water

Reticulum (hardware stomach): 5% of
stomach, heavy foreign items are trapped
here
Ruminant Stomach (cont.)



Omasum (many plies): 8% of stomach,
absorbs water
Abomasum (true stomach): 7% of
stomach, typical enzyme activity
Rumination= regurgitation, re-chewing
of food
Rumination (regurgitation)




After rumen if full, it lies down to ruminate
(chew its cud)
Cattle spend from 5-7 hours ruminating,
broken up into 6-8 periods
Regurgitation is the process of forcing the
feed back into the mouth for chewing
Done through a series of muscular
contractions and pressure in the rumen and
reticulum
Avian stomach/gizzard





Since chickens have no teeth, they swallow
food whole and it’s stored in the crop
Feed in proventriculus are secreted by the
glandular stomach and mixed with feed
The feed moves to the gizzard and is ground
Epithelium breaks the feed into smaller
particles, further mixing proventricular
digestie juices with the feed in the gizzard
The end of the digestive system is the vent
Small & Large Intestines

Small Intestine: long coiled tube
connecting stomach to large intestine
– rest of the digestion and absorption takes
place here
– surface covered with villi (surface area)

Large Intestine: Caecum, colon, rectum
– absorbs water (makes feces more solid)
– some vitamins & minerals absorbed here
– Cecal Fermenters (Horse): similar to rumen