Animal, Plant

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Animal, Plant Soil Science

• Lesson C3-2
• Animal Digestion

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Interest Approach

• Show the students a transparency of one of the
  digestive systems. Ask the students, What is
  this? When you have gotten the correct answer,
  ask the students, Why is it important for
  livestock producers to understand this? Lead
  discussion to Objective 1 of the lesson.

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Objectives

• Identify the various types of digestive systems
  found in animals.
• Identify the major parts of the digestive system
  and describe their functions.

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Terms

• abomasum
• absorption
• amino acids
• anus
• avian digestive system
• bile
• cecum

• chyme
• crop
• cud
• digestion
• digestive system
• enzymes
• eructated
• feces
• gizzard

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Terms

• intestinal juice
• monogastric digestive system
• omasum
• organs
• pancreatic amylase
• pancreatic juice

• pepsin
• pseudo-ruminant digestive system
• reticulum
• rumen
• ruminant
• ruminant digestive system

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Terms

• rumination
• salivary amylase
• salivary maltase
• stomach
• trypsin
• villi

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What are the various types of digestive systems
found in animals?

• Knowledge of the different types of
  digestive systems is critical in
  selecting the proper feeds
  for livestock.
• Understanding the chemical and physical changes
  that occur during the digestive process leads to
  more efficient livestock feeding.
• Digestion is the process of breaking down food
  into simple substances that can be absorbed by
  the body.
• Absorption is the process of taking the digested
  parts of food into the bloodstream.

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What are the various types of digestive systems
found in animals?

• The digestive system consists of the parts of the
  body involved in chewing and digesting food.
• This system also moves the digested food through
  the animals body and absorbs the products of
  digestion.
• Different species of animals are able to digest
  certain types of feeds better than others.
• This difference occurs because of the various
  types of digestive systems found in animals.
• There are four basic types of digestive systems
  monogastric (simple), ruminant (polygastric),
  pseudo-ruminant, and avian.

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What are the various types of digestive systems
found in animals?

• A. The monogastric digestive system, or simple
  digestive system, contains a single-chambered
  stomach and is the type found in humans, swine,
  dogs, and cats.
• The stomach is a muscular
  organ that stores ingested
  food and moves it
  into the
  small intestine.

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What are the various types of digestive systems
found in animals?

• The stomach secretes acid that has a low pH of
  1.5 to 2.5.
• The low pH destroys most bacteria and begins to
  break down the food materials.
• Animals with this type of digestive system are
  better adapted to the use of concentrated feeds,
  such as grains, than to the use of large
  quantities of roughages.

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What are the various types of digestive systems
found in animals?
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What are the various types of digestive systems
found in animals?

• B. The ruminant digestive system, or polygastric
  digestive system, contains one large stomach
  divided into four compartments and is the type
  found in cattle, sheep, and goats.
• An animal with this kind of digestive system is
  called a ruminant.
• Due to the complexity of its digestive system, a
  ruminant can make good use of roughages.
• Forty-four percent of the roughages fed are
  digested.
• The compartments of the stomach, in the order of
  digestion, are rumen, reticulum, omasum, and
  abomasum.

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What are the various types of digestive systems
found in animals?

• 1. The rumen is the largest section
  of the stomach and the first
  compartment that the food enters.
• It accounts for approximately 60
  percent of the stomach.
• The rumen contains bacteria and
  other microbes that promote fermentation.
• The rumen is designed so that food can be
  ingested, eructated (belched up), chewed, and
  then swallowed again.

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What are the various types of digestive systems
found in animals?

• 2. The reticulum is the second segment of the
  stomach.
• It is sometimes considered an extension of the
  rumen.
• The reticulum has honeycomb-like ridges.
• It aids in keeping the food in the rumen mixed
  with water and saliva until it is the right
  consistency.
• Once the right consistency is reached, the
  mixture can pass on into the lower digestive
  tract.

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What are the various types of digestive systems
found in animals?

• 3. The omasum is a small compartment that is the
  main sight for water absorption.
• The particles are squeezed and dehydrated, as
  well as sorted.
• The compartment acts as a filter for the abomasum.

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What are the various types of digestive systems
found in animals?

• 4. The abomasum, or true stomach, is the site
  of digestion.
• It secretes gastric juices consisting of
  hydrochloric acid and pepsin.
• These juices kill and then digest the microbes
  that have passed with the food materials from the
  rumen.
• The abomasum is similar to the stomach in a
  monogastric animal.

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What are the various types of digestive systems
found in animals?

• C. The pseudo-ruminant digestive system is the
  type found in animals that eat large amounts of
  roughages but do not
  have stomachs with several compartments.
• This type of digestive system
  performs some of the same
  functions as the type
  found in
  ruminants.

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What are the various types of digestive systems
found in animals?

• A pseudo-ruminant can utilize large amounts of
  roughages because of its greatly enlarged cecum
  and large intestine.
• Such an animal often eats forages as well as
  grains and other concentrated feeds.
• Examples of pseudo-ruminants are
  horses, rabbits, guinea pigs,
  and hamsters.

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What are the various types of digestive systems
found in animals?

• D. The avian digestive system is the type found
  in poultry.
• This system differs greatly
  from any other type.
• Since a bird has no teeth,
  no chewing is involved.
• The esophagus empties
  directly into the crop.

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What are the various types of digestive systems
found in animals?

• The crop is where the food is stored and soaked.
• From the crop, the food makes its way to the
  gizzard.
• The gizzard is a very muscular
  organ, which normally contains
  stones or grit that
  grinds the
  food.
• Digestion in the avian system
  is very rapid.

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What are the major parts of the digestive system
and their functions?

• The digestive system is made up
  of a number of organs, which
  are parts that
  perform specialized
  functions.
• The digestive system begins at the mouth, where
  food enters the body, and continues to the anus,
  where undigested material exits the body.
• The digestive systems of most livestock are very
  similar in terms of the organs they contain.
• Some of the major parts of a digestive system and
  their functions are

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What are the major parts of the digestive system
and their functions?

• A. Mouth and esophagusThe chewing action of the
  mouth and teeth breaks, cuts, and tears up the
  food.
• This increases the surface area of the
  food particles and aids in the
  swallowing process.
• Saliva not only stimulates the taste
  of the food but also contains the
  enzymes salivary amylase and
  salivary maltase.

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What are the major parts of the digestive system
and their functions?

• Enzymes are organic catalysts that speed up the
  digestive process.
• Salivary amylase changes starch to maltose, or
  malt sugar.
• Salivary maltase changes maltose to glucose.
• Chewed food passes from the mouth to the stomach
  through a muscular tube called the esophagus.

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What are the major parts of the digestive system
and their functions?

• B. Monogastric stomachWhen food enters the
  stomach of a monogastric animal, gastric juices
  begin to flow.
• The fluids come from
  glands in the wall of
  the stomach.
• The juices contain
  from 0.2 to 0.5 percent
  hydrochloric acid.
• This acid stops the action of the amylase from
  the mouth.

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What are the major parts of the digestive system
and their functions?

• The gastric juices also contain the enzymes
  pepsin, rennin, and gastric lipase.
• Pepsin breaks the proteins in the food into
  proteoses and peptones.
• The muscular walls of the stomach churn and
  squeeze the food.
• Liquids are pushed on into the small intestine.
• The gastric juices then act on the solids that
  remain in the stomach.

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What are the major parts of the digestive system
and their functions?

• C. Ruminant stomachThe four parts of the
  ruminant stomach are rumen, reticulum, omasum,
  and abomasum.
• A ruminant typically eats
  rapidly.
• It does not chew much of
  its food before swallowing.
• The solid part of food goes
  into the rumen.

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What are the major parts of the digestive system
and their functions?

• The liquid part goes into the reticulum, then
  into the omasum, and on into the abomasum.
• In the rumen, the solid food is mixed and
  partially broken down by bacteria.
• When the rumen is full, the animal lies down.
• The food is then forced back into the mouth, and
  rumination occurs.
• Rumination is the process of chewing the cud.
• The cud is a ball-like mass of food brought up
  from the stomach to be rechewed.

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What are the major parts of the digestive system
and their functions?

• On average, cattle chew their
  cuds about six to eight times
  per day.
• Five to seven hours each day
  are spent in rumination.
• The rumen and the reticulum contain millions of
  bacteria and protozoa.
• It is the bacterial action in the rumen that
  allows a ruminant to use large amounts of
  roughage.
• The bacteria can change low-quality protein into
  the amino acids needed by the animal.

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What are the major parts of the digestive system
and their functions?

• Amino acids are compounds that contain carbon,
  hydrogen, oxygen, and nitrogen.
• They are essential for growth and maintenance of
  cells.
• Bacteria also produce
  many of the vitamins
  needed by the animal.

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What are the major parts of the digestive system
and their functions?

• D. Small intestineThe partly digested food that
  leaves the stomach enters the small intestine as
  an acidic, semifluid, gray, pulpy mass.
• This material is called chyme.
• In the small intestine, the chyme
  is mixed with three digestive
  juices pancreatic juice, bile,
  and intestinal juice.

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What are the major parts of the digestive system
and their functions?

• 1. Pancreatic juice, secreted by the pancreas,
  contains the enzymes trypsin, pancreatic amylase,
  pancreatic lipase, and maltase.
• Trypsin breaks down proteins not broken down by
  pepsin.
• Some of the proteoses and peptones are broken
  down by trypsin into peptides.
• Proteoses, peptones, and peptides are
  combinations of amino acids.

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What are the major parts of the digestive system
and their functions?

• Proteoses are the most complex compounds, and
  peptides are the simplest.
• Pancreatic amylase changes starch in the food
  into maltose.
• Sugar and maltose are broken down even further by
  maltase.
• They are then changed into a simple sugar called
  glucose.
• Lipase works on fats in the food, changing them
  into fatty acids and glycerol.

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What are the major parts of the digestive system
and their functions?

• 2. Bile is a yellowish-green, alkaline, bitter
  liquid produced in the liver.
• Bile is stored in the
  gallbladder in all animals
  except the
  horse.
• Bile aids in the digestion
  of fats and fatty
  acids.
• It also aids in the action
  of the enzyme lipase.

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What are the major parts of the digestive system
and their functions?

• 3. Glands in the walls of the small intestine
  produce intestinal juice.
• Intestinal juice is a fluid that contains
  peptidase, sucrase, maltase, and lactase, all
  enzymes used in digestion.
• Proteoses and peptones are broken down by
  peptidase into amino acids.
• Starches and sugars are broken down by sucrase,
  maltase, and lactase into the simple sugars
  glucose, fructose, and galactose.

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What are the major parts of the digestive system
and their functions?

• E. CecumThe cecum, or blind gut, is found
  where the small intestine joins the large
  intestine.
• It has little function in
  most animals.
• In a pseudo-ruminant,
  the roughages consumed
  are
  digested by the
  bacterial action in the cecum.

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What are the major parts of the digestive system
and their functions?

• F. Large intestineThe main function of this
  organ is to absorb water.
• Material not digested and absorbed in the small
  intestine passes into the large intestine.
• The key to absorption in the large intestine is
  the small fingerlike projections on the walls,
  called villi.

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What are the major parts of the digestive system
and their functions?

• Food materials not digested or absorbed are
  called feces.
• These materials are moved through the large
  intestine by muscles in the intestinal walls.
• The undigested part of food is passed out of the
  body through the anus, the opening at the end of
  the large intestine.

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Review

• What are the various types of digestive systems
  found in animals?
• What are the major parts of the digestive system
  and their functions?