1. Harvest forages from unproductive land

2. Synthesis of vitamins (B,K) by microbes

3. Convert NPN to proteins by microbes

4. Eat a lot of food in a short time

1. Large GI tract

2. Degrade proteins in rumen

3. Metabolic disorders from high grain diets (DA, ketosis, acidosis)

• Lips, tongue, lower incisor teeth, dental pads
• Determine what an animal eats

• Grazers (cattle): plump & piston-like
• Browsers (sheep): slender & pointed

Only one set in a lifetime

Move bilaterally - side to side

Fully developed in cattle (2-3 yrs) and sheep (4 yrs)

Cattle have 32 teeth

1. Regulates pressure, reverse peristalsis, drives regurgitation

2. Movement in both directions constantly

3. Sphincters @ top and bottom

4. Esophageal Groove: shunts milk to abomasum

• Enzyme: only lipase from nasolabial gland
• Buffers: control pH of rumen for bacterial environment
• Lubrication, bolus formation, and transportation
• Mastication causes release of saliva

Reticulum, Rumen, Omasum: nonglandular epithelium

- Store food, delay passage, absorb water & VFAs

- No secretion

Abomasum: glandular epithelium

Lined with papillae that are dense in ventral sac & lower rumen because that is where absorption takes place.

Larger papillae w/ forage diet, smaller w/ grain diet.

Papillae growth stimulated by butyrate.

Function of:

1. Omasum

2. Abomasum

Omasum: Water Absorption

Abomasum: glandular structure w/ parietal cells that secretes HCl for protein digestion (gastric acid)

- All parts have villi, each villus has a lacteal
Duodenum: scretion of pancreatic enzymes, mixing, little absorption, brings pH up with bicarbonate secretion

Jejunum

Ileum

- No digestion or enzymatic secretions

- Cecum: microbes (microbial protein), B vitamins, & VFA's absorbed

* Microbial protein does not contribute to protein because no gastric acid to break down

 - Water and electrolyte absorption & storage

- Methane (CH4) & CO2 absorbed into bloodstream & expired

Spiral: muscles squeeze in a spiral - sheep - pelleted feces

Flaccid: feces form pies (cows)

- Lobulated, undivided gland

- Function: detoxification & modificatio of blood, synthesis of bile, metabolizes CHO/fat/protein, stores vitamins (fat soluble)

- Blood enters through portal vein, exits through hepatic vein

- Detoxifies by attaching an H20 soluble molecule

- Modifies blood by adding/synthesizing albumin, which metabolizes lipids

Endocrine: insulin (anabolic, Islet cells) & glucagon (catabolic)

Exocrine: enzymes

- Lobulated gland

- Function: digestive enzymes, electrolytes, hormones

What are the three unpaired glands?

And the one lone gland?

Palatine, Pharyngeal, Labial 

Nasolabial Gland

1. Serous

2. Mucous

3. Mixed

• Alkagenic: buffers the acid in the rumen
• Thin & watery, makes rumen "liquid"
• Continuous flow, not stimulated 

• Mucogenic, thick
• Glycoproteins: protein source for microbes
• Function: ease of swallowing, lubrication
• Stimulated by eating

• Some serous, some mucous
• Induced secretions

1. Lubrication/Moistening of Feed (increases density, moves through rumen)
2. Mastication
3. Buffering Capacity (rumen microflora, bicarbonate & phosphates)
4. Recycling of Nitrogen (urea in saliva, important for survival in low quality feed)
5. Maintain rumen fluid
6. Palatability
7. Lipase Activity (Nasolabial gland)
8. Antibodies (IgG's, IgE's, plasma = isotonic with saliva)
9. Nutrients for microbes (urea, glycoproteins, P, Mg
10. Bloat Prevention (saliva = antifrothing, no emulsion - no gas cap)

1 % Dry Matter

Na+, K+, Ca²⁺, Bicarb, HPO₄^2-, Cl-, N, S

pH: 8.1 - 8.4 (Forage Ruminant: 6.8 - 6.2)

Cattle: 150 L/day (50 gal)

Sheep: 6-10 L/day (4.2 gal)

Feed type, palatability, activity (eating, ruminating, resting)

* Longer eating time - more chewing - more saliva

* Feed forage first - more saliva

MIXING

- Aids in attachment of microbes to feedstuffs (by exposure)

- Movement to the omasum

- Rumination

- Regurgitation

- Eructation

Primary: mixing

- Reticulum becomes 1/2 normal size

- Feedstuffs floating on top are pushed down, dense particles sink

Secondary: eructation (30 s)

- Most methane & gases expired via lungs

Reticulorumen contracts, cardia flooded w/ fluid & particles, animal takes a deep breath, increased pressure in thorax, cardia opens, reverse peristalsis occurs.

Rechews bolus w/ molars.

Increases SA of particles, removes air pockets, increases density, causes to sink in rumen

Slow, prolonged contractions

Feedstuffs leave omasum independent of the body.

1. Bacteria (10¹⁰-10¹¹/mL)

Obligate & Facultative Anaerobes

3/4 bound, 1/4 free

2. Protozoa (10⁵-10⁶/mL): obligate anaerobes

3. Fungi (10⁷/mL): strict anaerobes

4. Mycoplasma (10⁵-10⁷/mL)

5. Bacteriophage (10⁷/mL)

• 200 different species, highly conserved, different concentrations
• Ciliated, flagellated
• Wide variety of substrates (starch, bacteria)
• Classify based on substrate used
• Can use multiple substrates

• No protozoal nitrogen
• Decrease in methane production
• Decrease in fiber digestion
• Decrease in ruminal insoluble protein digestion
• Increase in biohydrogenation (dbl bond to single bonds)
• Increase in ruminal starch digestion
• Increased Cu absorption 
• Changes in bacteria & fungi conc.
• Change in rate of passage
  * Bacteria eat dead protozoa!

1. Energy Source: C - ATP, protein & FA synthesis

2. Nitrogen: bacteria, protozoa, fungi use NH3

3. Minerals

4. Vitamins

Microminerals: P, K, Mg, Fe, Ca

- Mg = limiting for microbes

Macrominerals: Mn, Co, Mb

* Cofactors for enzymatic reactions!

• Biotin, PABA - hoof health
• Coenzyme M - methane synthesis
• Hemins, cytochromes - used for transport
• Branch chain VFA's - for synthesis of branch chain amino acids
• Phenylpropionic Acid - byproduct of fiber digestion, one cellulose helps another
• Aromatic Amino Acids - ring structure cannot be synthesized in rumen (Tyrosine, Phenylalanine, Tryptophan)

Competitive: for nitrogen, protozoa eating bacteria, bacteriophages, fungal infections, bacteriocins

Beneficial: use of breakdown products

Ex: cellulose - cellulodextrins - cellobiose - glucose; puts intermediates back into rumen for further breakdown

Attached to protozoa (rumensin)

Inside the protozoa (hydrogenosome)

Free Floating

Electron Sinks

1. Biohydrogenation
2. Propionate: longer chain, more hydrogen. Feed more starch/glucose, decrease methane production.
3. Oxaloacetate, Malate (see glycolysis) - need slow release
4. CH₄ - waste of energy, contributes to greenhouse gases

Factors That Affect Microbial Balance

1-5

1. Diet - microbes adjust to balance chemical & physical nature of feed
2. Plant species & soil fertility (minerals, N, alkaloids)
3. Climate
4. Eating Behavior
5. Physiological Status - pregnant, stressed. Increased salivation, ROP. Higher liquid conc. from saliva increases ROP. Extreme cold - increase ROP - more opportunitiy to eat (energy)

Factors that affect microbial balance

(6-10)

RUMEN DEVELOPMENT. 

go. 

Process: 

Salivary Output

Outcome?

Process: 

Rumination

Output?

Process: 

Rumen Movement

Outcome?

Process: 

Gas Production

Outcome?

Process:

Absorption Through Wall

Outcome?

Pectin, cellulose, hemicellulose, lignin. 

Lignin = indigestible, everything is all mixed up with lignin so accessibility is reduced. 

Rhamnogalacturonic Acid

Found in middle lamella

Cements the cell walls together 

Highly digestible

Xylans, glucans, mannans, arabinozylans, and arabinogalactans

Flexibility of cell wall

Grasses: higher content

Legumes: lower content (Alfalfa = 10%)

Highly digestible

Beta-1,4 linked glucose

H₂ bonds

Synthesized continuously 

Important for rigidity

Crystalline and amorphous types have different digestibilities

Hydroxycinnamic Acids

High in mature plants

Primarily in legumes

Considered indigestible

Silica

Waxes

Silica: cements lignin, usually nonentity but can be a problem

Waxes, chlorophyl: nutrients

Enzyme 1 = Beta 1,4-gluconase(endo); high molecular weight polymers

Enzyme 2 = cellobiohydrase; breaks down cellopentoses, cellotrioses, cellobioses

Enzyme 3 = Beta-glucosidase; breaks down cellobioses

Enzyme 4 = cellobiosidases; converts to glucose

* Glucose production stimulates Beta-1,4-Gluconase

Hemicellulose

- Digestibility?

- Associations?

- Higher in grasses or legumes?

100% digestible, but not in naturally occuring forages

Complex Molecule

Closely associated with lignin - low digestibility

High in grasses, low in legumes

• What are the components of the cell wall? 
• Label on a forage analysis?
• Digestibility?

• Cellulose, hemicellulose, pectin, heat damaged protein
• Neutral Detergent Fiber
• 20-80%

• What are the components of ADF?
• Digestibility?
• Why is the digestibility different from NDF?

• Cellulose, lignin, heat damaged protein
• 50-90%
• Higher digestibility becuase it is more impacted by the amount of heat damaged protein

Starch, fat, soluble protein, NPN, sugars, pectins

95-100%

Starch Digestion:

• Molecular Pathway?
• Steps?

• Starch → Dextrins  → Maltoses  → Glucose

1. Attachment of Bacteria: depends on access (barley vs. corn)
2. Secrete endo and exo enzymes that break α1-4,  α1-6 bonds in amylose & amylopectin

1. Heat: makes grain more soluble. ex: steam roll
2. Use Moisture. Ex: high moisture corn
3. Time in rumen
4. Mechanical Action: grinding, cracking, rolling. 
5. Use a blend of grains (barley, corn, and wheat) to create a continuum of digestion.

↑ SA, ↑ Rate of Passage, ↑ Digestibility

Also! Sheep are good at chewing. Do not need to process grains.

How many hours after feeding does peak VFA production occur? 

What does the pH look like at this point?

4 hours

pH is almost at it's peak (most basic)

• Absorbed across the ruminal papillae (which increase SA)
• Concentration dependent passive diffusion
• Blood flows by & has a lower concentration of VFA's, so they cross from rumen to blood. 
• More absorption in lower pH because the VFA's can pass directly, without having to wait to be converted to an acid. (Have to be in acid form to cross epithelium)