2. GI Part 9

Question 1

where doe fermentative idgestion occur

Answer 1

specialized compartments localized before the stomach (forestomach in ruminants) or after the stomach and small intestine (cecum and colon in horses)

Question 2

what kind of microbes are responsible for fermentative digestion

Answer 2

bacteria
fungi
protozoa

Question 3

what origin are enzymes of

Answer 3

microbe origin

Question 4

what is associated with fermentative digestion

Answer 4

regurgitation and remastication of food in order to provide more finely divided material and thereby a greater surface area for microbial digestion

Question 5

what side of the animal is the rumen on

what is the reticulum close to

Answer 5

rumen is on left side of animal

reticulum is close to the heart

Question 6

what do the pillars of the rumen do

Answer 6

separate the sacs of the rumen

can move, play an important role in mixing of digesta

Question 7

what are the forestomachs lined with

Answer 7

stratified squamous epithelium

Question 8

what is considered the true stomach and what side is it mostly on

Answer 8

abomasum

mostly on right side of animal

Question 9

what is the largest compartment in the newborn ruminants stomach

Answer 9

abomasum

Question 10

describe forestomach development after birth

Answer 10

enlargement of the forestomach occurs rapidly after birth, but rate depends on diet type and contact with adult ruminants

solid feeds accelerate development
inoculation of microorganisms from adult ruminants

nonruminant period – birth to 3 weeks
transitional period – 3-8 weeks

Question 11

describe rumen protozoa

Answer 11

most are ciliated and belong to genus Isotricha or Entodinium

grouped by size – big, medium, small

grouped by morphology – flagellates, ciliates

Question 12

ruminal environment:
substrate availability
temperature
fluids
pH
osmolality

Answer 12

substrate availability – food intake regulated by volume, structure, energy, palatability

temperature – about 0.5-1 degree C above body temperature

fluids – drink water and saliva

pH - 5.5-7 (acid synthesis and acid reabsorption, buffer substances coming from saliva and rumen epithelium)

osmolality – 260-400 mOsm/L

Question 13

describe the ruminal ecosystem

Answer 13

protozoa ingest large numbers of bacteria and hold bacterial number in check

protozoa may also play a role in starch and protein digestion

Question 14

how do protozoa play a role in starch and protein digestion in the rumen

Answer 14

prolong digestion of these substances – ingest them and protect them from bacterial action

Question 15

describe the syntropy (symbiosis) of the rumen

Answer 15

the waste products produced by one species serve as a substrate for another

for example cellulose digestion by species A produces a waste that species B uses to digest protein
protein digestion by species B produces a waste that species A uses to digest cellulose

Question 16

ruminal layers

Answer 16

top — gas
fiber mat (intense fermentation)
intermediate zone (intense fermentation)
bottom – liquid zone (moderate fermentation)

Question 17

what are VFAs form carb, protein, and fat digestion by rumen microbes used for

Answer 17

propionate – goes to liver and is used for glucose synthesis by gluconeogenesis

acetate and butyrate g– o to all tissues and are used for energy

acetate – goes to adipose tissues to create fatty acids

Question 18

what do cell walls of plants have and why is it important

Answer 18

has a large portion of carbohydrates which are important for stability and rigidity of the growing plant (structure carbs)

Question 19

what are some plant carbs

Answer 19

cellulose
hemicellulose
pectin

Question 20

what enzyme hydrolyses cellulose, hemicellulose, and pectin

Answer 20

cellulase

Question 21

what happens to cellulose, hemicellulose, and pectin after hydrolysis

Answer 21

after hydrolysis, monosaccharides are released from the polysaccharide

Question 22

are the monosaccharides released from cellulose, hemicellulose, and pectin after hydrolysis available for absorption by the animal

Answer 22

no they are not

they are further metabolized by the microbes

Question 23

what are the products of protein and carb fermentative digestion in the forestomachs

what happens to these products

Answer 23

glucose
other monosaccharides
short chain polysaccharides

these products are no available to host animals, they are absorbed into the cell bodies of the microbes

Question 24

what happens to glucose within the microbial cell and what does it produce

Answer 24

glucose enters the glycolytic pathway to produce 2 pyruvate from one glucose molecule (plus 2 NADH and 2 ATP which is used by the microbes)

Question 25

what type of digestion is fermentative digestion and what are the products

Answer 25

anerobic

products are VFA (SCFA)

Question 26

what are the primary VFA

Answer 26

acetic acid (acetate)

propionic acid (propionate)

butyric acid (butyrate)

Question 27

pathway of VFA production by the rumen and products – acetate

Answer 27

glucose –> pyruvate –> acetyl CoA –> acetate

products
4 ATP; 4 NADH/FADH2; 0 O2

Question 28

pathway of VFA production by the rumen and products – butyrate

Answer 28

glucose –> pyruvate –> acetyl CoA –> butyrate

products
3 ATP; 2 NADH/FADH2; 0 O2

Question 29

pathway of VFA production by the rumen and products – propionate

Answer 29

glucose –> pyruvate –> propionate

products
4 ATP; 0 NADH/FADH2; 1 O2

Question 30

pathway of VFA production by the rumen and products – propionate + acetate

Answer 30

glucose –> pyruvate –> lactate –> propionate + acetate

products
3 ATP; 0 NADH/FADH2; 0 O2