Rumen physiology

Question 1

what does ruminare mean

Answer 1

to chew over again (latin)

Question 2

why is the cud not acidic

Answer 2

comes from the first and second compartments that have a more neutral pH

Question 3

true v. pseudoruminants

Answer 3

• true: 4 compartment stomach

- pseudo: 3 compartments (no omasum)

Question 4

2 theories of ruminant evolution

Answer 4

• “eat and run”

- detoxification of plant substances

Question 5

what % of digestion do ruminant microbes account for

Answer 5

70%

Question 6

does rumen wall secrete enzymes or not?

Answer 6

no

Question 7

functions of rumen (4)

Answer 7

• storage
• soaking
• physical mixing and breakdown
• fermentation

Question 8

what does pregastric fermentation consist of (3)

Answer 8

• bacterial synthesis of water soluble vitamins and vitamin k
• bacterial synthesis of amino acids and protein
• breakdown of fibrous feeds

Question 9

what is wall of reticulum lined with? does it secrete enzymes?

Answer 9

• lined with mucous membrane

- no enzymes

Question 10

function of reticulum

Answer 10

moving ingested feed into rumen or omasum

Question 11

what is omasum filled with

Answer 11

muscular laminae

Question 12

function of omasum

Answer 12

reduce particle size of ingesta

Question 13

is abomasum glandular or nonglandular

Answer 13

glandular

Question 14

where does reticular (esophageal) groove extend from

Answer 14

cardia to omasum

Question 15

steps in rumination (4)

Answer 15

• regurgitation
• remastication
• resalivation
• reswallowing

Question 16

eructation

Answer 16

elimination of CO2 and CH4 (endproducts of fermentation)

Question 17

advantages of pregastric fermentation (6)

Answer 17

• utilization of cellulose as energy source
• conversion of NPN to microbial protein
• N recycling
• microbial detox of plant compounds
• reduction of B-vitamin req
• absorption of microbial end products

Question 18

disadvantages of pregastric fermentation (3)

Answer 18

• can lose energy from fermentation as heat, methane
• amino acid balance may not be improved
• many drugs can’t be fed orally

Question 19

is the rumen oxidating or reducing

Answer 19

reducing

Question 20

what is rumen rich in and deficient in

Answer 20

• rich in organic matter

- deficient in readily metabolizable compounds

Question 21

range of DM % of rumen contents

Answer 21

7-15%

Question 22

what % of body weight does rumen comprise of

Answer 22

7-15%

Question 23

what % of total stomach volume is rumen

Answer 23

80-85%

Question 24

does rumen secrete digestive juices

Answer 24

no

Question 25

how are end products/wastes from fermentation removed

Answer 25

diffusion across rumen wall

Question 26

2 mechanisms for keeping rumen pH near neutrality

Answer 26

- continuous influx of saliva (phosphate-bicarb buffer, some urea/mucous, no enzymes) - diffusion across rumen wall (more VFA diffuse into blood than omasum)

Question 27

rumen temperature

Answer 27

34-40 C, may be as high as 41 in active fermentation

Question 28

rumen gases

Answer 28

- CO2 (65%) - CH4 (27%) - H2 (0,2% --> used to reduce CO2 to CH4) - N (7%) - trace H2S, O2

Question 29

rumen facultative anaerobic bacteria

Answer 29

O2 scavenging activity to maintain anaerobic conditions

Question 30

how does urea enter rumen

Answer 30

feed supplement, saliva, diffusion across rumen wall --> source of NH3

Question 31

what bacteria have higher urease activity

Answer 31

adherent bacteria (also scavenge O2)

Question 32

ecological niches

Answer 32

- liquid phase: free-living microbial groups in fluid (25%) - solid phase: microbial groups w/ food particles (70%) - rumen epithelium: microbial groups attach to animal cells (5%)

Question 33

growth of microbes adhered to feed particles

Answer 33

- net growth rate less than liquid dilution rate | - growth rate related to solids turnover

Question 34

growth of microbes adhered to rumen wall

Answer 34

relatively slow net growth rate

Question 35

rumen microbial population (5)

Answer 35

- bacteria - archae - ciliated protozoa - flagellated protozoa - fungi - bacteriophage

Question 36

functions of bacteria (9)

Answer 36

- cellulolytic - amylolytic - hemicellulolytic - pectinolytic - ureolytic - proteolytic - methanogenic - glucolytic - lipid utilizers

Question 37

what does rumen hydrolyze fatty acids (triglycerides) into

Answer 37

free fatty acids, glycerol

Question 38

biohydrogenation

Answer 38

- follows hydrolysis or lipolysis - caused by rumen microbes - addition of H to fatty acids with double bonds - converts all double bonds --> saturated FA

Question 39

synthesis of lipids

Answer 39

odd-carbon chain and branched-chain FA

Question 40

how does most fat enter SI

Answer 40

as non-esterified FA that are highly saturated

Question 41

effects of defaunation (removing protozoa) - VFA concentration: - acetate/butyrate concentration: - propionate concentration: - ammonia concentration: - lactic acid concentration: - bacterial numbers: - protein degradation: - cellulose digestion:

Answer 41

- VFA concentration: dec - acetate/butyrate concentration: dec - propionate concentration: inc - ammonia concentration: dec - lactic acid concentration: inc - bacterial numbers: inc - protein degradation: dec - cellulose digestion: dec

Question 42

role of fungi

Answer 42

- synthesize enzymes - more effective in cellulose digestion - enterases (not in bacteria) for hemicellulose/ligin - penetrate plant cuticle - pectin degradation - grain digestion - choline synthesis

Question 43

relationship between ruminal bacteria and fungi

Answer 43

inverse relationship (bacteria produce bacteriocin-like substance to inhibit fungi)