DIGESTIVE PHYSIOLOGY OF HERBIVORES

Question 1

bacteria are abundantly present in 3 locations

Answer 1

1. rumen- foregut fermenting species
2. cecum- hindgut fermenting species
3. colon- hindgut fermenting species

Question 2

bacteria anaerobically digest carbohydrates:

Answer 2

• including cellulose and hemicellulose
• results in synthesis of short chain fatty acids (SCFA)
• SCFA also referred to as volatile fatty acids
• acetate, butyrate, propionate
• VFAs- energy source

Question 3

bacteria degrade protein

Answer 3

• products of degradation used to synthesize microbial protein
• microbial protein provides the host with essential AA

Question 4

bacteria hydrolyze lipids

Answer 4

• liberate fatty acids from the glycerol backbone

- hydrogenate fatty acids

Question 5

bacteria can also

Answer 5

synthesize all B vitamins
synthesize vitamin K
detoxify many plant toxins

Question 6

Foregut Fermenters- Ruminants

RUMEN

Answer 6

four chambered stomach:

• rumen
  - largest chamber (can hold up to 25L)
  - storage vat or food
  - fermentation vat
  - surface of papillae
  - carbohydrates: fermented to SCFA and gases
  - protein: degraded and reformed into microbial protein
  - fat: hydrolysed

Question 7

Foregut Fermenters- Ruminants

RETICULUM

Answer 7

rumination filter (honeycomb like tissue)
rumen /reticulum mixing (2-step process)
1st step: ingesta filtering
2nd step: eructation: gas release

Question 8

Foregut Fermenters- Ruminants

OMASUM

Answer 8

digesta pump (reticulum --> abomasum )
absorbs water and minerals

Question 9

Foregut Fermenters- Ruminants

ABOMASUM

Answer 9

true stomach 
secretory stomach (pepsinogen and HCl) 
protien digestion

Question 10

4 Rs of Rumination

Answer 10

1. regurgitation
2. re-mastication
3. re-insalivation
4. re-swallowing

Question 11

Foregut Fermenters - Pseudo ruminants

Answer 11

• foregut fermenting species
• expanded/sacculated stomach
• foregut microbial population very similar to ruminants
• can ferment/digest cellulose and hemicellulose

Question 12

hind-gut fermenters- cecum dedicated

Answer 12

post-gastic fermentation

• simple/single stomach
• enlarged/haustrated cecum
• distinct colon
• smaller herbivores

Question 13

hindgut fermenters- colon dedicated

Answer 13

post gastric fermentation 
simple/single stomach
distinct cecum 
enlarged/haustrated colon 
larger herbivores