Transcript Digestive Systems 2

Animal Science
Animal Digestion
Objective 1
Name, locate and describe the functions of
the parts of the digestive systems of
ruminant and nonruminant animals.
• Beef:
– Mouth- point at which ingestion
takes place and where cud is
chewed.
• Also, the body is stimulated to
secrete saliva.
• Teeth- provide
mechanical digestion
of feed by breaking,
cutting, and tearing up
food.
• The increase surface
area aids in the chewing
and swallowing
process.
• Salivary Glands– secrete saliva which moistens the feed and
stimulates taste.
– Saliva contains the enzymes,
– Enzymes are organic catalysts that speed up
chemical reactions without being altered by the
reaction.
Saliva includes:
• Water: moistens consumed feed and aids in the
taste mechanisms.
• Mucin: lubrication aid for swallowing.
• Bicarbonate Salts: acts as a buffer to regulate
pH of the stomach.
• Enzyme: salivary amylase initiates
carbohydrate breakdown.
• Mature horses can produce 10 gal/day; cows- 12
gal/day; and sheep- 2 gal/day.
• Esophagus: hollow muscular tube that transports
ingesta from the mouth to the stomach;
• Ingesta material is moved by a series of muscular
contractions referred to as peristatic waves.
• Also serves as a storage for food (crop) in
chickens.
• Cardiac Sphincter: valve at the junction of the
stomach and esophagus.
Stomach: hollow, pear shaped ,
muscular digestive organ.
Functions: (Sight of Digestion)
- Storage
of ingested
feed.
- Muscular
movements causing
physical breakdown.
- Secretes digestive
juices:
1) Hydrochloric
Acid
2) Pepsin
3) Rennin
Stomach cont.
• Stomach contents approximately a pH of 2
(bacterial effect).
• Material leaving the stomach is called chyme.
Parts of the stomach-simple stomach
• Cardia sphincter- see above
• Esophageal region: non-glandular area surrounding
the cardia
• Cardiac gland region: contains cells that produce
primarily mucus (protects stomach lining)
• Fundic gland region: contains cells that provide the
gastric secretions needed for the initial stages of
digestion.
• Parietal cells: produce hydrochloric acid.
• Chief cells: produce enzymes or precursors of enzymes
• Pyloric gland region: contains cells that produce
mucus and some proteolytic enzymes.
• Pylorus sphincter: at the beginning of the small
intestine which controls passage of material (chyme)
out of the stomach
Small Intestine
• Divided into 3 sections.
– Duodenum: first sections
• Receives secretions from:
– Pancreas: acts on proteins, carbohydrates and lipids
– Liver: bile (stored in the gallbladder) breaks down
fat. *Horses do not have gallbladders
• Active site of digestion
– Jejunum: middle section; active in nutrient
absorption
– Ileum: last section; active in nutrient absorption
Small Intestines
• Walls of the S.I. are lined
with a series of fingerlike
projections called villi,
which in turn have minute
projections called
microvilli that increase the
nutrient absorption area.
• Each nutrient has a specific absorption site. Each
villus contains an arteriole and venule, together with
a drainage tube of the lymphatic system, a lacteal.
• The venules ultimately drain into the portal blood
system, which goes directly to the liver; the lymph
system empties via the thoracic duct into the vena
cava.
• S.I. contents are approximately pH 6 to 7.
• Sight of digestion and absorption.
– Passive absorption = results from diffusion or movement
from high concentrations to low concentrations.
– Active absorption = transport of molecules across the
intestinal lining.
• (villi) engulf the molecules and then actively transport these
molecules to either the bloodstream or the lymph.
• Feed is carried to the liver where it is detoxified.
Large Intestine
• Divided into 3 sections
– Cecum:
•
•
•
•
first sections;
size varies considerably in different species;
little functional significance in the pig.
Horses contain an active flora of bacteria similar to the
microbial population in rumen compartment of ruminants.
– Bacterial breakdown of cellulose and other
carbohydrate material to produce VFAs (acetic,
propionic and butyric) thus, the horse can utilize
fibrous feeds.
– Site of bacterial synthesis of water-soluble vitamins
and protein.
• Colon:
– middle section;
– largest part of the L.I.
– Primary area of water restoration from intestinal
contents.
• Rectum: last section of the L.I. and the end of the
digestive tract before the unabsorbed material
(feces) is excreted out the anus.
• Functions of the L.I.
– Site of water restoration
– Secretion of some mineral elements
• calcium
– Storage reservoir of undigested GIT contents.
– Bacterial fermentation:
• Synthesis of some water-soluble vitamins and
vitamin K.
• Some bacterial breakdown of fibrous ingredients.
• Synthesis of some protein
– Limited absorption of feedstuff from the L.I.
• Anus: eternal opening where unabsorbed materials
(feces) are expelled from the body.
• Teeth:
Beef Cattle
– Designed to shred fibrous material on the side
of the mouth.
• Saliva:
– Contains no enzymes
– Provides source of N (urea), P, Na
• Utilized by rumen microorganisms
– Aids in maintaining an appropriate pH in the
rumen.
Cattle Digestive System
Beef Cattle Stomach
• Divided into 4 compartments
–
–
–
–
Reticulum
Rumen
Omasum
Abomasum
12 week old calf rumen
Reticulum (Honeycomb)
• First compartment and not completely separated
from the rumen;
– esophagus opening (cardia) is common to both reticulum
and rumen compartments.
• Walls are lined with mucus membrane containing
many intersecting ridges that subdivide the surface
into honeycomb-like compartment;
– this wall arrangement traps hardware (nails, wire, and
etc.) and does not allow it to proceed through the
remainder of the GIT (gastrointestinal tract)
Reticulum (Honeycomb)
• The wall does not secrete any enzymes.
• The reticulum functions in moving ingested
feed into the rumen or into the omasum and
in regurgitation of ingesta during
rumination.
Rumen (paunch)
• Large, hollow, muscular compartment that extends
from the diaphragm to the pelvis and almost entirely
fills the left side of the abdominal cavity.
• The wall of the mature rumen contains small tongue
like projections called papillae, which can be readily
identified by the naked eye. The walls aid in the
secretion of enzymes.
Rumen (paunch)
• Functions include:
– Storage
– Soaking
– Physical mixing and breakdown.
Rumen (paunch)
• Fermentation chamber:
– ideal environment for microbial organisms
• (bacterial and protozoa)
• it is moist, warm, anaerobic, desirable in PH and there is an
irregular introduction of new ingesta and a more or less
continual removal of fermented digesta and end products of
digestion.
• Various types of bacteria are found with typical counts
approaching numbers of 25 to 50 billion per milliliter of
ruminal fluid.
Rumen (paunch)
• This extensive pregastric fermentation result in:
– Bacterial synthesis of water-soluble vitamins and
vitamin K.
– Bacterial synthesis of amino acids and protein.
• As the bacteria move out of the rumen, they will be degraded
in the lower portion of the host animal’s GIT and serve as a
source of amino to the host animal.
Rumen (paunch)
• Breakdown of fibrous feeds (high in cellulose).
Bacteria contain enzymes to rupture cellulose
bonding as well as starch bonding.
– Rumen compartment is quite undeveloped at birth and
may be functional by 6 to 8 weeks of age.
Omasum (many plies)
• The omasum is a spherical organ filled with
muscular laminae studded with short, blunt
papillae. The walls secrete no enzymes.
• The omasum is located to the right of the rumen
and reticulum.
• The omasum appears to be instrumental in
reducing particle size of ingesta before it enters
the abomasum and some absorption of water.
Abomasum
(true or glandular stomach):
• First glandular portion of the ruminant GIT
(walls secrete enzymes).
• Located below the omasum and extends
caudally on the right side of the rumen.
• In general, the gland regions of the
abomasum correspond to the gland regions
in the simple stomach of the nonruminant.
Other Peculiarities of the Ruminant
Digestive System
• Esophageal (or reticular) groove
• Rumination
• Eructation (belching of gas)
Esophageal (or reticular) groove
• A passageway that extends from the cardia to the
omasum, formed by two heavy muscular folds or
lips, which can close to directly, or open and
permit the ingesta to enter the rumen and
reticulum.
• Functions to allow milk consumed by the suckling
animal to bypass the reticulorumen and escape
bacterial fermentation.
• Does not appear to remain in older animals.
Rumination
• A process that permits an animal to forage and
ingest feed rapidly, then complete the chewing at a
later time; steps include regurgitation of feed,
remastication, re-salivation and finally reswallowing.
• The regurgitation step is preceded by contraction
of the reticulum; probably a reverse peristalsis in
the esophagus is the major factor in moving the
material up to the mouth, where excess liquid is
squeezed out and swallowed.
Rumination cont.
• The regurgitated material consists largely of
roughage and fluid with little if any
concentrate.
• Cattle average about 8 hours per day
ruminating. One rumination cycle requires
about 1 minute, of which 3 to 4 seconds is
utilized for both regurgitation and reswallowing.
Eructation (belching of gas)
• Microbial fermentation in the rumen results
in production of large amounts of gases
(primarily carbon dioxide and methane),
which must be eliminated.
• Contractions of the upper sacs of the rumen
force gases forward and down; the
esophagus then dilated and allows the gases
to escape.
Eructation cont.
• Bloat is a common problem in ruminants in which
gas cannot escape. This creates a distention of the
rumen, which can be seen on the left side of the
animal; in most cases of bloat, a stable froth or
foam is produced in the rumen. This interferes
with normal belching and gas accumulates.
Therefore, control measures must prevent foam or
break it rapidly after it has formed.
*ALL OTHER SYSTEMS ARE THE SAME.
Avian Digestive System