Download Livestock Nutrition

Digestion in Animals
Objectives
• 1- Describe the nonruminant
(monogastric), ruminant, and avian
digestive systems.
• 2- Describe the process of digestion
in animals.
• 3- Describe the absorption of
nutrients in animals.
Digestive Systems
• Digestion is a process that breaks
feed down into simple substances
that can be absorbed by the body.
• This usually involves mechanical,
chemical and enzymes.
• The compounds are then
absorbed into the blood stream.
Digestive tract
• Also known as the gastrointestinal
tract or the alimentary tract.
• Begins at the mouth and ends at the
anus.
Three kinds of digestive systems.
• Non-ruminant (monogastric)
• Ruminant (polygastric)
• Avian
Non-ruminant digestive systems
• Swine, horses & humans.
• Single compartment stomach.
• Includes, mouth, teeth, tongue,
salivary glands, esophagus, stomach,
small intestine, liver, pancreas, cecum,
large intestine, rectum and anus.
Parts of Swine Digestive Tract
Parts of Horse Digestive System
Mouth, part of digestive system.
• The mouth contains the teeth, tongue, and
salivary glands.
• Chewing action (mechanical part of
digestion).
• Food is cut and torn in the mouth, then
mixed with saliva, which is produced in three
different places.
• Three paired sets of salivary glands, located
under the lower jaw and under the ears.
Mouth
• Saliva contains water, mucin,
bicarbonate salts and enzymes.
• Horse saliva does not contain
enzymes.
• In swine, saliva contains the enzymes
salivary amylase and salivary maltase.
Enzymes
• Enzymes work in the whole digestive
process, from mouth to anus.
• Enzymes are organic catalysts that
cause and/or speed up digestive action.
• However, enzymes remain unchanged
in this process.
• A weak acid solution will halt enzyme
action.
Digestion in the Mouth
• Saliva stimulates the taste nerves.
• Water moistens the feed for chewing and
swallowing.
• Mucin lubricates the feed for swallowing.
• Bicarbonate salts buffer the pH in the
stomach.
The Tongue
• The tongue gathers feed in the mouth.
• Directs the feed in the throat for
swallowing.
• Mixes feed.
Esophagus
• A tube like passage which leads from the
mouth to the stomach.
• Peristaltic waves send feed down the
esophagus, (muscle contractions).
• The cardia, located at the end of the
esophagus prevents feed in the stomach
from coming back into the esophagus. (
non-ruminants)
Stomach
• Pear shaped, muscular organ, receives feed,
where it is further broken down by muscle in the
stomach wall.
• Gastric juices, secreted by the glands in the
stomach wall, start to flow the moment
masticated feed enter the stomach.
• Gastric juices have about 0.2 to 0.5 percent HCl.
Stomach
• 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.
• The stomach of the horse has less
muscular activity than that of other
species, causing an increased tendency
toward digestive disorders.
Horse Stomach
• The stomach of a horse is smaller,
compared to other species, in relation to
the size of the animal.
• Therefore, it is more desirable to feed
horses in smaller amounts at one time but
provide more frequent feedings.
Small Intestine
• Active digestion takes place here.
• Proteins are further broken down
• Starch is changed to maltose.
• Fats in the feed are broken down into
fatty acids glycerol and
monoglycerides.
• Bile from the liver helps emulsify fats.
Large Intestine in Swine
• The cecum is the first part of the large
intestine
• The small intestine does the majority of
absorption.
• Cecum in swine has little or no function.
• The colon is the middle and largest part of
the large intestine.
Large Intestine, Horses
• Divided into cecum, large colon, small colon
and rectum.
• Cecum is an important organ in horses.
• The large intestine makes up approximately
60% of the total digestive tract.
• Horses can use large amounts of roughage
because of the presence of bacteria in the
cecum and colon.
Large Intestine, Horses
• IMPORTANT- because the large intestine
of the horse usually contains substantial
quantities of ingested material, impaction
occurs easily.
• This impaction is the start of what horse
ailment?
Large Intestine
• The main function of the L intestine is to
absorb water from the material passing
through.
• In the Horse, the small colon is the site of
most of the water resorption.
Ruminant Digestive System Mouth
• Saliva of ruminants does not contain
enzymes, it contains buffers which
neutralize acid produced in the rumen.
• The rumen contents are maintained at
approximately a pH of 6-6.5.
• This pH level promotes microbial growth in
the rumen.
• Mature cows produce about 12 gallons of
saliva per day while sheep produce 2 gal.
Ruminant Digestion Stomach.
• The stomach of the ruminant contains four
compartments:
• Rumen or paunch
• Reticulum or honey comb
• Omasum or many plies.
• Abomasum or true stomach.
Ruminant Digestion
• Ruminants eat rapidly swallowing much of
their feed without chewing.
• Solid feed goes to the rumen.
• The liquid part also goes into the rumen.
But passes quickly to the reticulum, then
through the omasum and on into the
abomasum.
Esophageal Groove
• These two muscular folds for a passage
way from the cardia, ( the end of the
esophagus), to the omasum.
• Its major function appears to be to allow
milk ingest by a nursing animal to bypass
fermentation in the rumen. Serves no
purpose in adult ruminants.
Bovine Digestive system
• Identify location
and function of
each of the
parts of the
Bovine
digestive
system.
Rumination
• After the ruminant animal has filled the
rumen with feed it lies down to ruminate,
(chew its cud)
• Cattle spend from 5-7 hours ruminating,
broken up into 6-8 rumination periods.
• Regurgitation is the process of forcing the
feed back into the mouth for chewing.
• This is done through series of muscular
contractions and pressure in the rumen
and reticulum.
Rumen Microorganisms
• Rumen and reticulum contain millions of
microorganisms called bacteria and
protozoa.
• Together, these tiny organisms feed on
the fibrous material in the rumen.
• They digest cellulose and compiles starch,
synthesize protein and synthesize
vitamins.
• 50-65% of the starch is digested in the
rumen.
Functions of the Rumen
• A large fermentation vat and account for about
50-85% of the total utilization of the digestible
dry matter in the ration.
• Saliva mixed with feed helps control the pH of
the rumen.
• Feed material stays in the rumen and
reticulum area from about two hours to several
days.
• Type of feed influences time, Concentrates
pass more quickly than roughages.
Function of the Reticulum
• Lined with intersecting ridges that form
honeycomblike projections.
• Hardware that is ingested is trapped in this
area and generally do not move further
through the digestive system.
• Feed is moved back and forth between the
rumen and reticulum
Function of the Omasum
• The omasum grinds and squeezes the
feed.
• Little or no digestive action.
• The material leaving the omasum is 60-70
percent drier than the material entering it.
Function of the Abomasum
• Digestion here is much the same as it is in
a monogastric animal.
• There is little or no digestion of fat,
cellulose or starch.
• pH level of 3.5-4.0.
• The feed becomes highly fluid as it passes
into the small intestine.
Avian Digestive Systems
• Different from nonruminant and ruminant.
• Feed in proventriculus are secreted by the
glandular stomach and mixed with feed.
The feed next moves to the gizzard.
• Epithelium breaks the feed into smaller
particles, further mixing of proventricular
digestive juices with the feed in the
gizzard.The end of the digestive system is
the vent.
Absorption of Nutrients
• Absorption is the process of taking
nutrients from the digested feed into the
blood and lymph systems.
• In nonruminants most absorption takes
place from the small intestine with a lesser
amount being absorbed from the large
intestine.
• In ruminants there is some absorption of
nutrients through the wall of the rumen.
Absorption of Nutrients
• The two methods of absorption are
diffusion and active transport.
• Diffusion is the movement of molecules
from an area of high concentration to one
of low concentration.
• Active transport is the movement of
molecules from one area to another
requiring the expenditure of energy.
• Amino acids and glucose move by active
transport.
Summary
• Digestion is breaking feed down into simple
substances that can be absorbed by the body.
• Digestion occurs when feeds are broken up
mechanically and acted upon by enzymes and
other digestive juices.
• Most absorption of nutrients after digestion takes
place in the small intestine, although some
absorption occurs in the rumen.