RuminantsRuminants........

100-150 L

5-8 L

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

The rumen papillae The rumen papillae are key to VFA are key to VFA absorption;absorption;health is criticalhealth is critical

The honeycomb of the The honeycomb of the reticulum is well suited reticulum is well suited for sorting particles by for sorting particles by size and for ruminationsize and for rumination

The folds and plies of the The folds and plies of the omasum allow ingesta to omasum allow ingesta to be trapped and squeezed be trapped and squeezed to allow dehydration to allow dehydration prior to delivery to the prior to delivery to the abomasumabomasum

RumenRumen OmasumOmasumReticulumReticulum

Ruminants: Some BasicsRuminants: Some Basics

A. Rumination: re-gurgitation, re-mastication, re-insalivation, re-swallowingB. Eructation: 12-30 L per minute; 3-17 times per minuteC.DigestionD. Fermentation

I. Physical: I. Physical: 4 specialized stomach compartments

Ruminants: Some BasicsRuminants: Some Basics

A. Cellulase complexB. HemicellulasesC. LysozymeD. Nitrogen Capture (NPN)

II. Chemical:II. Chemical: specialized Enzymes & Processes

Because of these enzymes and abilities, ruminants can utilize feedstuffs that provide little to no nutritional benefit to non-ruminants.

Ruminants: Some BasicsRuminants: Some Basics

A. Fiber Digestion

B. Starch Digestion

C. Urea Utilization

The nutrients presented to thecow or steer by the rumen arevery different than those enteringthe rumen as feed.

Rumen Function and Rumen Function and DevelopmentDevelopment

A. The 4 compartments or four chambers:

1. RumenRumen: digestion and fermentation vat (VFA production)

2. ReticulumReticulum: mixing aid (feed, water, saliva)

3. OmasumOmasum: Dehydration by compression/squeezing

removes 60-70% of water from ingesta

4. AbomasumAbomasum: “true stomach”; acid secretion, lysozyme

I.I. Organization, function, and special relationshipsOrganization, function, and special relationshipsamong compartmentsamong compartments

Rumen Function and Rumen Function and DevelopmentDevelopment

1. 1. Rumen: digestion and fermentation vatRumen: 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)

Rumen Function and Rumen Function and DevelopmentDevelopment

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

Rumen ciliate protozoaRumen ciliate protozoa

Rumen Function and Rumen Function and DevelopmentDevelopment

C. complex polysacharides 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

D. Its The VFA 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

Some BasicsSome Basics

Digestion

Fermentation

All CHO Must PassThrough Pyruvate toBecome VFA

Some BasicsSome BasicsNon-structural polysaccharides Structural polysaccharides

VFA, H+

Pyruvate Lactate

E. Rumen pH Must Be Defended

1. VFAs (acids) produced must be removed

2. Passively absorbed across rumen wall

3. Helps maintain pH at 5 6.7

Some BasicsSome Basics

4. Saliva also provides buffering capacity

cattle: 180 L per day 180 L per day (70% water entering rumen)

5. Saliva is rich in Na, K, PO4, HCO3

Rumen papillae epitheliumRumen papillae epitheliumperforms at least 3 majorperforms at least 3 majorfunctions:functions:

• ProtectionProtection• MetabolismMetabolism• AbsorptionAbsorption

VFA are absorbed passively; VFA are absorbed passively; thus, the concentration gradient thus, the concentration gradient from lumen to blood supply from lumen to blood supply must be maintained. Metabolism must be maintained. Metabolism of some VFA within the cells of of some VFA within the cells of the papillae help ensure a the papillae help ensure a gradient.gradient.

II. Rumen DevelopmentII. 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

Some BasicsSome Basics

Rumen Development Begins EarlyRumen Development Begins Early

1. Depends on:

A. Fibrous Diet

B. Inoculation

C. VFA Stimulation

Some BasicsSome Basics

QuestionsQuestions