1. Ruminants....

2. Ruminants: Some Basics
Distinguishing Features
I. Physical: 4 specialized stomach compartments
A. Rumination:
regurgitation, remastication,
re-insalivation, reswallowing
B. Eructation: L per minute;
3-17 times per minute
C. Digestion
D. Fermentation

3. L
Collectively, these organs occupy almost 3/4ths of the abdominal cavity, filling
virtually all of the left side and extending significantly into the right.
3-5 L
5-8 L

4. Rumen Reticulum Omasum The honeycomb of the
reticulum is well suited for
sorting particles by size and
for rumination
The folds and plies of the
omasum allow ingesta to be
trapped and squeezed to
allow dehydration prior to
delivery to the abomasum
The rumen papillae
are key to VFA absorption;
health is critical
Rumen
Reticulum
Omasum

5. Ruminants: Some Basics
Distinguishing Features
I. Physical: 4 specialized stomach compartments
A. Rumination:
regurgitation, remastication,
re-insalivation, reswallowing
B. Eructation: L per minute;
3-17 times per minute
C. Digestion
D. Fermentation

6. Ruminants: Some Basics
Distinguishing Features
II. Chemical: specialized enzymes and processes
A. Cellulase complex
B. Hemicellulases
C. Lysozyme
D. Nitrogen Capture (NPN)
Because of these enzymes and abilities, ruminants can utilize feedstuffs that provide little to no nutritional benefit to nonruminants.

7. Ruminants: Some Basics
Distinguishing Features
III. Microbial: specialized microbial population;
bacteria, protozoa, fungi
A. Fiber digestion
B. Starch digestion
C. Urea utilization

8. The nutrients presented to the cow or steer by the rumen are
Feed In
VFA
Microbial Protein
Vitamins
The nutrients presented to the
cow or steer by the rumen are
very different than those entering
the rumen as feed.

9. Rumen Function and Development
Organization, function, and special relationships
among compartments I.
A. The 4 compartments or four chambers:
1. Rumen: digestion and fermentation vat (VFA production)
2. Reticulum: mixing aid (feed, water, saliva)
3. Omasum: Dehydration by compression/squeezing
removes 60-70% of water from ingesta
4. Abomasum: “true stomach”; acid secretion, lysozyme

10. Rumen Function and Development
1. Rumen: digestion and fermentation vat
a. conditions must be maintained to support microbial growth
1. temperature, moisture, pH buffered
2. constant supply of nutrients
3. continuous removal of products of digestion/fermentation
(gases, VFA, ammonia)

12. Rumen Function and Development
b. products of fermentation provide bulk of energy to animal
1. Starch and cellulose digestion
2. Anaerobic metabolism (fermentation)
3. Volatile fatty acid (VFA) production

13. Rumen Function and Development
c. complex polysaccharides are digested to yield sugars that
are fermented to produce VFA
1. Structural polysaccharides: cellulose, hemicellulose
digested by cellulases and hemicellulases
2. Cellulase is not a single enzyme, but a complex (affinity factor
+ hydrolytic factor)
3. Protozoa engulf starch particles to digest them
4. Microbes attach to (colonize) fiber components and
secrete enzymes

15. Acetate, Butyrate, Propionate
Some Basics
d. it is the VFAs that provide the bulk of the energy to the ruminant
1. Bacterial sugar metabolism differs from that of aerobic organisms.
2. VFA are produced from pyruvate by fermentation
Polysaccharides
Galactose Sucrose Fructose Maltose
Glucose
Acetate, Butyrate, Propionate

16. Digestion Fermentation All CHO must pass through Pyruvate to
become VFA

17. Some Basics Pyruvate Lactate VFA, H+
Nonstructural polysaccharides
Structural polysaccharides
Pyruvate Lactate
VFA, H+
Rumen pH must be defended in the face of
organic acids and H+ production to prevent
acidosis.

18. Some Basics e. rumen pH must be defended
1. VFAs (acids) produced must be removed
2. Passively absorbed across rumen wall
3. Helps maintain pH at 6.7  .5
4. Saliva also provides buffering capacity
cattle: 180 L per day
(70% water entering rumen)
5. Saliva is rich in Na, K, PO4, HCO3

19. Rumen papillae epithelium
performs at least 3 major
functions:
protection
metabolism
absorption
VFA are absorbed passively; thus,
the concentration gradient from lumen
to blood supply must be maintained.
Metabolism of some VFA within the
cells of the papillae help ensure a
gradient.

20. Some Basics II. Rumen Development
A. Newborns are not functional ruminants
1. Lack sucrase
2. Limited amylase
3. Lactase: galactose, glucose
4. Ability to digest non-starch polysaccharides precedes that for starch

21. Some Basics B. Rumen Development Begins Early 1. Depends on:
a. fibrous diet
b. inoculation
c. VFA stimulation

23. Some Basics C. Inoculation occurs by: 1. Feed
2. Inter-animal contact (saliva)
3. Manure, soil
*occurs with isolation, but much slower and less completely