Digestion

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Digestion

• the process of breaking feed down into simple
  substances that can be absorbed by the body.

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3 metabolic processes that contribute to this
break down

• anabolism
• catabolism
• oxidation

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Anabolism

• is the set of metabolic pathways that construct
  molecules from smaller units.
• These reactions require energy
• Anabolism is powered by catabolism
• Examples "building up" organs and tissues.
• anabolic processes include the growth and
  mineralization of bone and increases in muscle
  mass.

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Catabolism

• the breakdown of body tissue into simpler
  substances and waste production

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Oxidation

• what happens to nutrients that provide energy for
  the animal

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Absorption

• refers to taking the digested parts of the feed
  into the bloodstream
• movement of nutrients across the lining of the
  intestinal tract into blood and lymph system.

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Metabolism

• the chemical reactions in cells
• The appetite of the animal is controlled by the
  hypothalamus gland

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Functions of the digestive system of animals

• 1. Ingestion (eating)
• 2.grinding
• 3.digestion
• 4.absorption of nutrients
• 5. elimination of waste

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Mechanical Activities of the Stomach

• mastication (chewing)
• deglution (swallowing
• regurgitation (throwing up)
• gastric and intestinal motility (peristalsis)
• defecation (eliminate waste)

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Chemical Activities of the Stomach

• Actions of enzymes and other substances produced
  and secreted by digestive glands

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Microbial Activities of the Stomach

• 1. activites of bacteria and protozoa (especially
  in the use of roughages)
• 2. substances produced and secreted by digestive
  glands

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Ruminants stomach is divided into four parts

• 1 rumen
• 2 reticulum
• 3 omasum
• 4 abomasum
• Examples cows, deer
• Ruminants are cud-chewing animals. They can
  digest large quantities of roughages (such as
  hay and pasture)

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Non-ruminants have simple, one-compartment
stomachs.

• Examples pig, horses, poultry, humans
• They need high-energy, low-fiber rations such as
  grain

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• Grains and protein supplements are called
  concentrates.
• most expensive part of a ration

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Roughages

• high fiber feeds such as hay, silage, and pasture
• 44 percent of the roughages cattle and sheep eat,
  they actually digest.
• 39 percent are digested by horses.
• 22percent are digested by swine
• Ruminants can digest large quantities of roughage
  because of the bacteria present in their
  digestive system.

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Mouth start of digestive tract

• saliva contains enzymes, salivary amylase,
  salivary maltase
• Horses saliva doesnt contain enzymes.
• Saliva moistens the feed for chewing and
  swallowing
• mucin lubricates the feed for swallowing
• prostaglandin secretions and bicarbonate buffer
  the pH in the stomach

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Enzymes

• organic catalysts that cause and or speed up
  digestive action

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Teeth

• Incisors Cutting or shearing food
• Premolars and molars Grinding food

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• Ruminants no upper teeth and a hard upper dental
  pad
• Hard palate roof of the mouth
• -Turns to soft palate toward the rear of the
  mouth
• Salivary glands
• -Common in mucous membrane lining of the mouth,
  except on the tongue, hard palate, and gums

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• Tongue Mass of muscle covered by a mucous
  membrane
• Covered with finger-like projects called papillae
• Contain taste buds
• Cheeks Are made mostly of muscle lined with a
  mucous membrane and line food up with teeth

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Pharynx

• Common passage for food and air
• Several structures open to the pharynx
• mouth
• nasal cavity
• Eustachian tubes from the ears
• larynx
• esophagus

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• Non ruminants have two striated muscles that
  control the passage of food in and out of the
  stomach

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Esophageal Groove

• Extends from the initial opening of the stomach
  to the omasum
• Causes food to bypass to the rumen and reticulum

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• Cardia Sphincter muscle located at the junction
  of esophagus and stomach
• Pylorus is another sphincter muscle located at
  the bottom of the stomach
• These control the passage of food in and out of
  the stomach

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Rumen

• 80 of the stomach
• food goes from the esophagus to this part of the
  stomach first
• -AKA - fermentation vat

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Digestion in the Ruminant

• Rumen provides favorable environment for
  microbial growth due to
• Buffered pH
• Temperature maintained at 101 to 103 degrees
• Primarily a liquid media
• Food supply replenished daily
• End products of digestion removed
• Anaerobic

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Rumen Feed Storage
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• Microbes use ammonia and amino acids, energy, and
  minerals for growth
• cheap type of ammonia urea

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Papillae (tripas)

• finger like lining of the rumen.
• honeycomb lining of the reticulum

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Reticulum

• food goes back and forth from the Rumen to
  Reticulum to break down to particle size
• Considered the honeycomb
• Site of Hardware Disease
• Helps move and regurgitate digesta
• Collects objects that shouldnt be in the
  digestive system.
• Nails
• Screws
• Baling wire

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Reticulum (Hardware Stomach or Tripe)
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• Function Site of microbial action absorption
  of Volatile Fatty Acids
• Pacemaker for rumen contractions
• Contractions start in reticulum spread to rumen
• Mixes rumen contents
• Heavy particles move to bottom, lighter ones
  float
• Lighter particles subject to rumination
• (Rumination regurgitation, remastication,
  resalivation, reglutition)

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Omasum

• Increases size but may squeeze some water out of
  the feed (H2O absorbed here)
• Acts like a filter, holds back feed stuff that
  hasnt been broken into smaller particles
• Regulates particle size flowing to abomasum/S.I.
• many piles, lamina propia
• -has a lot of leaves and folds called papillae
• -Function is unclear
• -Some mechanical digestion from lamina

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Omasum (manyplies)
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Abomasum

• (true stomach)
• everything done like a non-ruminants stomach
• Secretes digestive juices.
• Breaks down food stuff further for absorption.
• Absorbs some nutrients.

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Abomasum
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Eructation

• Belching of gas
• Improper eructation
• leads to bloat

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Gallbladder

• Horses dont have one
• It empties waste as bile through the common bile
  duct into the duodenum

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Pancreas

• produces the hormone insulin which deposited into
  the bloodstream
• located in the first loop of the duodenum

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Liver

• worn out red blood cells are destroyed here
• has a duct that merges with the pancreas and
  empties into the small intestines

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Bile

• yellowish-green, alkaline, bitter liquid
• aids in the digestion of glycerol and fatty acids

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Hydrochloric Acid

• Aids in the dissolving of minerals in diet

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Small Intestines

• work to break down solids
• The end product of digestion of protein are amino
  acids
• Go through the blood stream to cells.

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Villi

• Finger-like projections line small intestine
• Primary site of absorption of nutrients

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Duodenum

• first part of the small intestines
• secretions from the pancreas, liver, and
  intestinal walls occur here
• is secreted here.

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Jejunum

• middle part of the small intestines
• nutrient absorption occurs here

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Ileum

• last part of the small intestines
• nutrient absorption occurs here

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Layers in the intestine
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Large intestines

• Vitamins E and K are synthesized in the large
  intestine. These are fat soluble vitamins.
• Bacteria in the LI produce some amino acids, but
  mostly fatty acids
• Fatty acids energy
• Amino acids protein synthesis

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Large Intestine

• Divided into
• 1 cecum
• 2 blind pouch
• 3 colon
• 4 ends in the rectum and anus

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Cecum

• first part of the large intestine
• ruminants have bacteria here which allows it to
  use large amounts of roughages
• primary water absorption site.
• Fermentation occurs in the cecum, similar to the
  action that takes place in the fore-stomach of
  the ruminant

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colon

• middle and largest part of the large intestine

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Rectum

• Connects the small colon with the anus.
• Receives feces from the small colon, which formed
  the characteristic balls of horse manure.
• Reabsorbs water that was not absorbed in the
  cecum.

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