Fermentation

Question 1

In hindgut fermenters, where does the fermentation occur?

Answer 1

Caecum, colon

Question 2

Define fermentation, includes what the microbes provide enzymes for.

Answer 2

The metabolic action of bacteria, fungi and protoza. Microbes provide enzymes for hydrolysis of large molecules.

Question 3

How does fermentation differ to monogastric in terms of speed, alteration of substrates?

Answer 3

Slower than glandular secretion, substrates are altered to a much greater degree

Question 4

Why have vertebrates created a symbiotic relationship with microbies?

Answer 4

Because they do not produce cellulases (to break down cellulose)

Question 5

What % of DM is digested by bacteria?

Answer 5

70-80%

Question 6

What factors does microbiome composition vary with?

Answer 6

Diet, age, species, habitat

Question 7

What ions are contained in saliva, and what is their function?

Answer 7

Bicarbonate (HCO3-) and phosphate ions (PO4)3-, they buffer VFAs acidity

Question 8

what is the pH of the rumen?

Answer 8

6-7

Question 9

What can be the cause of a lower rumen pH

Answer 9

Grain fed animals

Question 10

Why do grain fed animals usually have a lower rumen pH

Answer 10

As the feed has a higher digestibility, more VFAs are produced, decreasing pH

Question 11

List the products of pyruvate (post-glycolysis) in fermentation.

Answer 11

Acetate, propionate, butyrate, H+, gases (CH4, CO2)

Question 12

List the order of acidity of the 3 main VFAs

Answer 12

Most: acetate
Middle: propionate
Least: butyrate

Question 13

Categorise ‘simple sugars’, ‘starch’ and ‘cellulose’ into soluble, storage and structural CHOs (and list their speed of digestion - fast, middle, slow)

Answer 13

Soluble: simple sugars (fast)
Storage: starch (middle)
Structural CHO: cellulose (slow)

Question 14

What % of VFAs are absorbed from rumen-reticulum

Answer 14

70%

Question 15

Of the remainder 30%, what % of is absorbed from the omasum

Answer 15

60-70%

Question 16

Are VFAs more easily absorbed in a dissociated or undissociated state?

Answer 16

Undissociated

Question 17

What does carbonic anhydrase catalyse to produce?

Answer 17

Produces carbonate and H+

Question 18

What products are produced from the deamination of amino acids

Answer 18

Ammonia (NH3) and VFAs

Question 19

List 3 non-protein nitrogen sources that ruminal microbes can synthesise microbial protein

Answer 19

Ammonia, urea, nitrates

Question 20

Where do ruminants recycle nitrogen from?

Answer 20

Ammonia, absorbed from deamination of protein in the rumen

Question 21

Name the 2 basic patterns of reticulorumen motility

Answer 21

Primary (mixing) contractions
Secondary (eructation) contractions

Question 22

Describe the primary contractions of the reticulorumen

Answer 22

Circular movement of ingesta in dorsal/ ventral sacs that moves denser material over cranial pillae

Question 23

How often do secondary ‘eructation’ contractions occur?

Answer 23

Every other primary contraction, immediately after

Question 24

What is the result of the eructation contractions?

Answer 24

Gas entering oesophagus and being eructated

Question 25

List the order of the primary mixing contractions of the reticulorumen

Answer 25

PARALLEL contraction of reticulum
CAUDAL moving contraction of DORSAL sac
CAUDAL moving contraction of VENTRAL sac
CRANIAL moving contraction of DORSAL sac
CRANIAL moving contraction of VENTRAL sac

Question 26

Describe the process of the secondary (eructation) contractions?

Answer 26

The dorsal blind sac has a cranial moving wave, which forces the gas cap cranially. The cranial sac relaxes and cranial pillar elevates so liquid ingesta moves away from cardia. This allows gas to enter the oesophagus.

Question 27

How often to primary/ mixing contractions occur?

Answer 27

every 1-3 minutes

Question 28

With the afferent and efferent fibres in the vagus nerve, what do the receptors monitor in regards to control of rumen?

Answer 28

Monitor distension, pH, concentration of VFAs, osmolality, tension receptors

Question 29

Name the 4 rumen zones.

Answer 29

Gas cap, rumen mat, slurry zone, liquid zone