Digestive System

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Digestive System

• Ruminants

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• The only way of finding the limits of the
  possible is by going beyond them into the
  impossible.Arthur C. Clarke

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Dentition - Cattle

• Incisors
• Pre-molars
• Molars
• Deciduous 20 (there are no deciduous molar and
  deciduous PM1)
• 0 0 3 (I C PM)
• 3 1 3
• Permanent 32 (No PM1)
• 0 0 3 3
• 3 1 3 3

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Eruption Deciduous Teeth
Teeth Age at eruption
1st Incisor (Di 1) Birth 2 weeks
2nd Incisor (Di 2) Birth 2 weeks
3rd Incisor (Di 3) Birth 2 weeks
4th Incisor (Di 4 or C) Birth 2 weeks
1st Cheek Tooth (Dp 2) Birth to few days of age
2nd Cheek Tooth (Dp 3) Birth to few days of age
3rd Cheek Tooth (Dp 4) Birth to few days of age
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Deciduous
Permanent
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Eruption Permanent teeth
Teeth Age at eruption
I 1 18 24 months
I 2 24 30 months
I 3 36 months
I4 or C 42 48 months
1st cheek tooth P2 24 30 months
P3 second cheek tooth 18 30 months
P4 third cheek tooth 30 36 months
M2 fifth cheek tooth 24 30 months
M3 sixth cheek tooth 24 30 months
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Cattle - Dentition

• 14 months
• complete deciduous
• short and broad
• bright ivory color
• space between Di 1 incisors

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How old?
Rostral
Rostral - lateral

• Teeth are longer and narrower
• Not touching at upper corner

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How old?
Eruption of one or more central incisors
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How old?
At least one of 2nd pair of incisors
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How old?
I3 36 months, I4 42 months
Peg teeth
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Dentition Sheep and Goats

• 2 (0/4 incisors, 3/3 pre-molars, 3/3 molars)
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• Animal under one year old no permanent teeth
• One year old (2 permanent teeth)
• Two years old (4 permanent teeth)
• Three years old (6 permanent teeth)
• Four years old (8 permanent teeth)
• Old animal, more than four years old

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Permanent Tooth Eruption

• Incisor (I1)1-1.5 years
• Incisor (I2)1.5-2 years
• Incisor (I3)2.5-3 years
• Incisor (I4)3.5-4 years
• Premolars1.5-2 years
• Molar (M1)3 months
• Molar (M2)9-12 months
• Molar (M3)1.5-2 years

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How old- Sheep?
Broken mouth
Wide spacing
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How old - Goats
Deciduous 10 months
Deciduous 2 weeks
10 yrs
1.5 2 yrs
3 yrs
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Digestive System

• Cranial fermentors
• Forestomach
• E.g. cattle, sheep and deer
• digest and extract energy from
• cellulose
• utilize the protein from fermentative
• microbes
• Caudal fermentors
• Cecal digestors
• E.g. horses and rabbits
• digest and extract energy from cellulose
• utilize dietary hexose sources directly

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Digestive system calf

• Esophageal groove
• first few weeks of life, the rumen, reticulum,
  and omasum are undeveloped
• By pass reticulum and rumen and goes directly
  into abomasum
• Grain and forage for rumen development 3 weeks
  age

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Fermentation Ecology

• Rumen inoculation
• 1 ml of rumen content 10 to 50 billion
  bacteria,1 million protozoa, variable numbers of
  yeasts and fungi
• Cellulolytic (digest cellulose)
• Hemicellulolytic (digest hemicellulose)
• Amylolytic (digest starch)
• Proteolytic (digest proteins)
• Sugar utilizing (utilize monosaccharides and
  disaccharides)
• Acid utilizing (utilize such substrates as
  lactic, succinic and malic acids)
• Ammonia producers
• Vitamin synthesizers vitamin B and K
• Methane producers

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Entodinium (Rumen Protozoa)
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Symbiotic Relationship

• Microbes provide to the ruminant
• Digestion of cellulose and hemicellulose
• Provision of high quality protein
• Production of VFA
• Provision of B vitamins
• Detoxification of toxic compounds
• Ruminants provide to microbes
• Housing
• Garbage removal
• Nutrients
• Optimal environment for growth

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Fermentation Ecology

• Rumen pH between 6 and 7
• Grain engorgement pH lt5.5
• protozoal populations decrease
• Products Sugars -gt VFAs
• acetic, propionic and butyric acids

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Volatile Fatty Acids

• Acetic acid
• is utilized minimally in the liver
• oxidized throughout most of the body to generate
  ATP
• Major source of acetyl CoA for synthesis of
  lipids.
• Proprionic acid
• is almost completely removed from portal blood by
  the liver
• In the liver, proprionate serves as a major
  substrate for gluconeogenesis, which is
  absolutely critical to the ruminant because
  almost no glucose reaches the small intestine for
  absorption.
• Butyric acid,
• most of which comes out of the rumen as the
  ketone beta-hydroxybutyric acid
• is oxidized in many tissues for energy production.

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Ruminant Anatomy

• the rumen or paunch
• reticulum or "honeycomb,"
• the omasum or book,"
• the abomasum or "true stomach."
• Esophagus gt reticulum gt rumen gt omasum gt abomasum
• CD

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Reticulum honeycomb

• Lies against the diaphragm
• rumino-reticulum connected by tissue
• Heavy objects fall
• Hardware disease (traumatic reticuloperitonitis)
• No enzyme secretion
• Formation of food bolus

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Rumen Paunch

• largest of the forestomaches
• sacculated by muscular pillars dorsal, ventral,
  caudodorsal and caudoventral sacs
• stratified squamous epithelium (Papillae lining)
• fermentation vat (25 gallons, anaerobic bacteria)
• Absorbs most VFA
• Healthy cows 1-2 minutes/contractions

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Omasum - book

• broad longitudinal folds or leaves
• Absorption of water
• Reduce particle size, ingesta between the leaves
  will be drier than in other compartments

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Abomasum true stomach

• This is the only compartment (also called the
  true stomach) with a glandular lining
• HCL and digestive enzymes (proteolytic enzymens
  mucin, pepsinogen, renin, lipase), needed for the
  breakdown of feeds, are secreted into the
  abomasum
• PH decreases from 6 gt 2.5
• Denatures proteins
• Kills bacteria and pathogens
• Dissolves minerals

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Digestive system - Ruminants

• The small intestine
• measures about 20 times the length of the animal
• duodenum, jejunum, and ileum.
• secretions of the pancreas and the gallbladder,
  which aid digestion
• Most of the digestive process is completed here,
  and many nutrients are absorbed through the villi
  (small finger-like projections) into the blood
  and lymphatic systems.
• Cecum
• junction of the SI and LI, where some previously
  undigested fiber may be broken down
• Function of cecum?
• Large intestine
• last segment of the tract through which
  undigested feedstuffs pass
• absorption of water is the primary digestive
  activity occurring in the large intestine
• Some bacterial digestion of undigested feed occurs

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Function of digestive tract

• Eructation (belching)
• Large quantities of gas, mostly carbon dioxide
  and methane, are produced in the rumen
• Rumination (4 phases)
• 35 to 40 percent of each day ruminating (cud
  chewing)
• During rest periods, feed boluses (cud) are
  regurgitated for rechewing to reduce particle
  size and for resalivation.
• Feed is more readily digested by rumen microbes
  as particle size is reduced
• Redeglutition swallowing

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Four Steps of Rumination

• Regurgitation
• Reverse peristalsis carries food to mouth
• Remastication
• Liquid squeezed from bolus and swallowed
• Bolus chewed
• Reinsalivation
• Adding more saliva
• Redeglutition
• Swallowing bolus and liquids

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Remastication and Redeglutition
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Digestive system - Ruminants

• Motility of the rumen and reticulum
• contractions mix the rumen contents, bring
  microbes in contact with new feedstuffs, reduce
  flotation of solids, and move materials out of
  the rumen
• Saliva production
• 50 to 80 quarts of saliva
• provides liquid for the microbial population,
  recirculates nitrogen and minerals, and buffers
  the rumen
• buffer for helping to maintain a rumen pH between
  6.2 and 6.8 for optimum digestion of forages and
  feedstuffs
• Vomiting
• Rare suspect toxins

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References

• Large Animal Clinical Procedures, Elizabeth
  Hanie. 2006
• http//www.fsis.usda.gov/ofo/tsc/bse_information.h
  tm
• http//www.fao.org/docrep/t0690e/t0690e05.htm
• http//www.infovets.com/books/smrm/C/C015.htm
• http//www.vivo.colostate.edu/hbooks/pathphys/dige
  stion/herbivores/index.html
• http//www.extension.umn.edu/distribution/livestoc
  ksystems/components/di0469-02.html
• faculty.fortlewis.edu/LASHELL_B/Nutr2-Rumdigestion
  .pdf
• http//www.das.psu.edu/research-extension/dairy/nu
  trition/calves/rumen
• http//www.pitt.edu/super1/lecture/lec30761/006.h
  tm