Lecture 43 11/28/23

Question 1

What is fermentation?

Answer 1

chemical breakdown of a substance by microorganisms

Question 2

Where does fermentation occur in foregut fermenters?

Answer 2

distinct compartments of the non-glandular stomach

Question 3

Where does fermentation occur in hindgut fermenters?

Answer 3

cecum and colon

Question 4

What environmental characteristics are needed for fermentation?

Answer 4

-neutral pH
-slow motility
-ability for microbes to survive and grow

Question 5

What types of microorganisms are found in the rumen?

Answer 5

anaerobic bacteria, fungi, and protozoa

Question 6

What are the interactions observed between the rumen microbes?

Answer 6

-waste of one organism is food for another
-synergistic digestion/microbes digest different things
-one microbe produces vitamins needed to promote the growth of others

Question 7

Which substrates from plant cell walls can be broken down by microbes?

Answer 7

-cellulose
-hemicellulose
-pectin

Question 8

Which substrate from plant cell walls cannot be broken down by microbes?

Answer 8

lignin

Question 9

How does plant age impact lignin amounts?

Answer 9

plants accumulate more lignin with age

Question 10

What happens to proteins and carbohydrates in ruminants?

Answer 10

rumen microbes use the same substrates that the host would use, potentially reducing digestion/absorption effeciency

Question 11

What are the characteristics of volatile fatty acids?

Answer 11

-major fermentative end products
-main energy source for ruminants
-absorbed in reticulum and omasum

Question 12

What are the main VFAs?

Answer 12

-acetate
-propionate
-butyrate

Question 13

What are the characteristics of a high-fiber diet?

Answer 13

-higher acetate and lower propionate
-less total VFAs
-higher rumen pH

Question 14

What are the characteristics of a high-starch diet?

Answer 14

-lower acetate and higher propionate
-more total VFAs
-lower rumen pH

Question 15

What are the characteristics of protein fermentation?

Answer 15

-amino acids are deaminated by gut microbes
-produce ammonia and VFAs
-act as energy source for the synthesis of microbial proteins

Question 16

Why is microbial protein synthesis important?

Answer 16

ruminants rely on it to meet their protein requirements

Question 17

When is microbial protein production most efficient?

Answer 17

when growth rate of the microbial mass is maximized

Question 18

Why is it important to have a balance of proteins and glucose?

Answer 18

to ensure proper energy for both protein synthesis & cell growth and cell maintenance

Question 19

Which substrates can be used by rumen microbes to produce proteins besides other proteins?

Answer 19

-ammonia
-urea
-nitrates

Question 20

What are the characteristics of urea recycling?

Answer 20

-hepatic urea originates from ammonia produced during protein metabolism by bacteria and the body
-urea can be secreted into urine or the rumen

Question 21

What happens to urea in the rumen?

Answer 21

-converted into ammonia
-enters nitrogen pool for microbial synthesis
-allows ruminants to efficiently conserve protein and nitrogen

Question 22

What are bypass proteins?

Answer 22

-proteins that pass through the forestomachs and into the intestine
-digested and absorbed in a similar fashion to monogastric proteins

Question 23

What conditions are needed for optimal fermentation?

Answer 23

-adequate substrate provided
-appropriate temp., molality, and oxygen conc.
-removal of indigestible waste
-absorption of VFAs
-buffering of acidic pH

Question 24

What is the path through the rumen?

Answer 24

-esophagus
-reticulorumen
-omasum
-abomasum
-duodenum

Question 25

What are the layers of ingesta in the rumen?

Answer 25

-gas cap -raft -rumen liquors

Question 26

What are the three main types of rumen contractions?

Answer 26

-mixing -eructation -regurgitation

Question 27

What are the characteristics of mixing contractions?

Answer 27

-keep rumen contents well-mixed -last 30-50 seconds

Question 28

What are the characteristics of eructation contractions?

Answer 28

-allow for CO2 and methane build up in rumen to escape -stretch receptors signal vagal afferents

Question 29

What are the characteristics of bloat?

Answer 29

-obstruction in esophagus prevents gas eruption -caused by diets high in saponins and/or grains that lead to dextrin slime production

Question 30

What are the characteristics of regurgitation contractions?

Answer 30

-bring large particles into mouth for additional chewing -initiated by presence of rumen raft -stimulates saliva secretion -occur every 2-3 minutes

Question 31

How does diet type affect regurgitation?

Answer 31

-high grain diets have smaller particles and require less regurgitation -high forage diets require more regurgitation

Question 32

What are the characteristics of dilution rate?

Answer 32

-rate of liquid flow through the rumen -% of total liquid leaving the rumen per hour -must be replaced by more liquid

Question 33

Why is a high fluid flow beneficial?

Answer 33

it washes away existing microbes and stimulates growth of new microbes

Question 34

Which signals provide control over rumen motility?

Answer 34

-stretch/distension -ingesta consistency -pH -VFA conc. -ionic strength

Question 35

How does raft size relate to rumen contractions?

Answer 35

-smaller rafts lead to less resistance to contraction and reduced muscle tension/motility -larger rafts lead to more resistance to contraction and increased muscle tension/motility

Question 36

What are the characteristics of pH?

Answer 36

-slightly acidic due to VFA production -hyperacidity suppresses rumen motility

Question 37

What are the main characteristics of hindgut fermentation?

Answer 37

-smaller particle size to start -digestible carbohydrates and protein are already mostly absorbed

Question 38

What are the functional segments of the hindgut fermenter's colon?

Answer 38

-cecum -ventral colon -dorsal colon -small colon

Question 39

What is the goal of haustral segmentation motility?

Answer 39

promotes mixing and brings VFAs in contact with mucosa for absorption

Question 40

What is the goal of propulsive peristalsis?

Answer 40

moving ingesta aborally

Question 41

What are the functions of retropulsive peristalsis?

Answer 41

-retaining ingesta for more mixing -allowing microbes to remain in colon instead of being flushed out -allowing small particles to pass while retaining large particles

Question 42

Where does retropulsive peristalsis occur?

Answer 42

distal left and distal right ventral colon

Question 43

What is the pelvic flexure?

Answer 43

an area of narrowing in the distal left ventral colon that is prone to impactions

Question 44

What are the characteristics of buffering?

Answer 44

-ileum secretes large amounts of bicarb. and phosphate buffers -high VFA conc. stimulates water secretion by large intestine crypt cells

Question 45

What is cecotrophy?

Answer 45

act in which hindgut fermenters consume fecal pellets for a "second chance" at the nutrients