Digestive System of Animals Animal Science Frameworks Presentation Unit 3.1

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Digestive System of Animals Animal Science
Frameworks Presentation Unit 3.1

• Mr. Sullivan

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Digestion

• Purpose reduce feed particles to molecules that
  can be absorbed into the blood
• Mechanical breakdown of food
• chewing
• Chemical breakdown of food
• HCl in the stomach
• enzymes
• Contractions of digestive tract

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Animals are classified by the types of food they
ingest

• Carnivore - animal products
• Dogs, Cats
• Herbivore - plant products
• Cattle, Sheep, Goats, Horses
• Omnivore - combination of plant and animal
  products
• humans, pigs

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Animals are also classified by the type of
stomach they have

• Monogastrics or non-ruminants
• Ruminants

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Monogastric Animals

• Monogastric one or simple stomach structure
• mostly carnivores and omnivores
• Very simple mink and dog
• Cecal digestion horse, rabbit or rat
• Sacculated stomach kangaroo

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Ruminant Animals

• Ruminant - 4 compartment stomach with the
  compartments before the true stomach
• herbivores
• cattle, sheep, goats and pseudoruminants (llamas)

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Digestion

• Prehension
• Bringing the food to the mouth
• Upper limbs, head, beak, claws, mouth, teeth and
  lips
• Mastication or chewing
• To crush the food, increase surface area and
  allow enzymes to act on molecules
• Carnivores need only to reduce the size of the
  particle
• Herbivores must chew continuously (40-50,000
  times a day)

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Monogastric Animal Digestive Tract

• Basic anatomy
• mouth
• stomach
• small intestine
• large intestine or colon

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Monogastric Animal Digestive Tract

• Feed passes from the mouth to the stomach through
  the esophagus
• To reduce the size of the feed particles
• From the stomach it passes through the
• duodenum (first part of the small intestine)
• Bile and pancreatic secretions enter here
• jejunum (second part of the small intestine)
• Absorption of nutrients
• ileum (third part of the small intestine)
• To split food molecules and absorb nutrients

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Monogastric Animal Digestive Tract

• Large Intestine
• water absorption
• feces formation
• Rectum

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Human and Pig Similarities

• Both are omnivores
• Cannot synthesize B complex vitamins
• Cannot synthesize amino acids
• Can become obese with increased food intake

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Monogastric Animal Digestive Tract

• Exceptions
• herbivores
• horses have a cecum (blind anterior end of the
  colon) where feed is fermented
• Cecum is posterior to optimum feed absorption
  area, thus advantages of the ruminant animal is
  lost

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Enzymes of the Digestive Tract

• Enzyme names often end in -ase
• and
• begin with a description of the substrate they
  act upon

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Enzymes of the Digestive Tract

• Enzyme Substrate Product
• Amylase Starch Dextrin, Disaccharides
• Chymotrypsin Peptides Amino Acid
• Peptides
• Lactase Lactose Glucose
• galactose

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Enzymes of the Digestive Tract

• Enzyme Substrate Product
• Lipase Lipids Fatty acids glycerides
• Pepsin Protein polypeptide
• Peptidase Peptides amino acid
• Sucrase Sucrose glucose
• Trypsin Protein polypeptide

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Monogastric Digestion

• Enzymes help breakdown large molecules
• Mouth
• amylase in saliva of humans and pigs breaks down
  starch to disaccharides and dextrin
• Stomach
• HCl - creates acidic environment
• pepsin - breaks proteins down polypeptides

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Monogastric Digestion

• Enzymes help breakdown large molecules
• duodenum
• Cells release hormones that act on pancreas and
  gall bladder
• secretin
• pancreozymin
• cholecystokinin

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Monogastric Digestion

• pancreas
• lipase
• lipids to fatty acids and glycerides
• trypsin
• proteins to polypeptides
• chymotrypsin
• peptides to amino acids and peptides
• amylase
• starch to disaccharides and dextrin

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Monogastric Digestion

• gall bladder
• bile
• produced in the liver
• emulsifies fats
• alkaline to neutralize stomach contents that are
  acidic
• small intestine
• amino acids, fatty acids and monosaccharides are
  available for absorption

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Ruminant Digestion

• mouth
• esophagus
• rumen
• reticulum
• omasum
• abomasum
• small intestine
• large intestine

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Ruminant Digestion

• rumen - 40 gallons in a cow
• large fermentation vat
• covered with papillae to increase the surface
  area
• microorganisms digest cellulose
• microorganisms synthesize amino acids from
  nonprotein nitrogen
• microorganisms synthesize B-complex vitamins

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Ruminant Digestion

• reticulum - 2 gallons in a cow
• lining looks like a honeycomb
• interacts with rumen to mix contents

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Ruminant Digestion

• omasum - 4 gallons in a cow
• many folds, perhaps to grind feed

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Ruminant Digestion

• abomasum - 4 gallons in a cow
• true stomach

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Ruminant Digestion

• Ruminants eat forage rapidly
• they regurgitate food (cud)
• and chew it again and swallowed
• Rumination - continuous reguritation, chewing and
  swallowing
• Eructation - elimination of gases (methane and
  carbon dioxide) in the rumen from fermentation

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Rumen Microorganisms

• Bacteria and Protozoa
• rumen environment is moist, warm, and provides a
  constant supply of nutrients
• entire population of organisms depending on the
  kind and quality of the feed
• when they are washed out of the omasum into the
  abomasum the acidic environment kills the
  microorganisms
• provide amino acids and some energy

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Ruminant Digestion

• Ruminants to not secrete amylase in their saliva
• bacteria and protozoa in the rumen and reticulum
  utilize starches and sugars- no glucose available
  for the ruminant
• microorganisms do produce volatile fatty acids
  (VFA) that are absorbed and converted to energy
• acetic, propionic and butyric acids
• major source of energy

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Energy Pathways in the Ruminant

• From Rumen to Abomasum
• Injestion materials
• Cellulose Starch Fat
• Complex Sugars
• Glucose
• VFAs

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Energy Pathways in the Ruminant

• Liver
• VFAs
• Glucose

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Ruminant and Monogastric Absorption in the small
intestine

• passive transport
• diffusion by concentration
• active transport
• villi engulf molecules
• to bloodstream or lymph system

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Rumen Microorganisms

• Bacteria and Protozoa
• rumen environment is moist, warm, and provides a
  constant supply of nutrients
• entire population of organisms depending on the
  kind and quality of the feed
• when they are washed out of the omasum into the
  abomasum the acidic environment kills the
  microorganisms
• provide amino acids and some energy