L26: Forestomach fermentation digestion Flashcards

1
Q

T/F: Fermentation is slower than glandular digestion

A

T

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2
Q

give an example of a rapidly ferementable carbohydrate and a slowly fermentable one

A

sugar is fast
starch is medium
fiber is slow

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3
Q

what is needed for optimal fermentation

A
  1. pH, moisture, ion composition, redox-potential
  2. slow movement/long transit times facilitate reaction time
  3. specific motility patterns
  4. continuous removal of waste products; release of gases
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4
Q

what are the fermentation chambers

A
  • forestomach
  • sub-region in stomach (ex: non-glandular region in horses)
  • hindgut (colon & caecum)
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5
Q

end products of fermentation

A
  • VFA
  • microbial protein
  • gases
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6
Q

rumen microbes are _____, they coexist with the mammalian host for mutual benefit

A

mutualists

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7
Q

microbes initiate the degradation of ______ and detoxify ________

A

cellulose
allelochemicals

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8
Q

what happens if VFAs accumulate in the rumen

A

they lower the pH but the buffer (saliva) & removal from fermantation chamber helps maintain pH and avoid rumen acidification

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9
Q

T/F: microbes are substrate specific

A

T

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10
Q

what are the ways in which animals acqurie B12

A

diet (dogs,cats,pigs) and or by microbial production (ruminants)

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11
Q

dietary Cbl (Cobalamin) is bound to what 2 proteins

A

R-protein and intrinsic factor (IF) forming complexes

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12
Q

what cells secrete intrinsic factor (IF)

A

parietal

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13
Q

where is R protein digested

A

duodenum

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14
Q

where can Cbl be stored

A

liver and muscle

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15
Q

what can cause insufficient Cbl levels / B12

A
  • insufficient dietary Cbl
  • insufficient transport proteins caused by inflammation in stomach / SI which reduces R protein and/or IF production
  • reduced microbial production due to cobalt deficiency in the diet of ruminant
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16
Q

although ruminant microbes can produce B12, it has to be supplemented with ?

A

Cobalt

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17
Q

what is microbial yield

A

mass of microbial dry matter / mass of substrate

18
Q

what things affect microbial yield

A
  • temperature
  • pH
  • dilution rate of rumen fluid
  • C:N ratio in diet
19
Q

increased C:N ratio

A
  • enough energy but insufficient N
  • available E gets used by microbes for maintenance rather than growth
20
Q

decreased C:N ratio

A
  • ample N to support growth, but insufficient E for maintenance
  • available E is used for maintenance rather than growth
21
Q

increased or decreased glucose/protein ratios will ____ the microbial yield

A

lower

22
Q

a matched glucose / protein ratio will ______ the microbial yield

A

maximize

23
Q

urea is formed in the ______ & is an an important source for _____

A

liver
NPN

24
Q

where does hepatic urea come from

A
  • deamination of endogenous amino acids
  • nitrogen absorbed as ammonium in rumen
25
Q

urea is mostly excreted via ?

A

urine
but in ruminants, it can be recycled and partially returned to rumen via saliva

26
Q

what does N flow to and from the rumen depend on

A

rumen ammonia concentration

27
Q

effect of high nutritional protein concentration on blood urea

A

causes high blood urea; most of which is secreted in urine

28
Q

how does low nutritional protein (w/ high CHO availability) affect the rumen

A

low rumen ammonia levels; stimulates nitrogen flow to rumen

29
Q

the ______ portion of urea is used as the building block for the production of protein by rumen microbes

A

nitrogen

30
Q

ammonia released from urea can go either of what 2 pathways

A
  1. production of microbial protein
  2. to the liver where it is detoxified and excreted in urine
31
Q

in a ______ system, microbial growth is characterized by 4 phases: lag, log, stationary and decline

A

closed

32
Q

why does microbial growth decline in a closed system

A

nutrients get exhausted and conditions (pH, Oxygen) become unfavorable

33
Q

the rumen is mostly an _______ system, so microbial growth is continuous

A

open
maintains cell population in exponential growth for long periods of time

34
Q

what makes the rumen an open system

A
  • feed input
  • gas release; VFAs absorbed
  • movement of rumen contents into omasum
35
Q

what makes the rumen not an entirely open system

A

no - little oxygen

36
Q

where in the GI tract is the IF-Cbl complex absorbed by endocytosis

A

ileum

37
Q

what is dilution rate

A

large saliva volumes stabilize pH & provide fluid for dilution

38
Q

what are the sources of nitrogen

A
  • protein
  • urea
  • ammonia
  • nitrate
39
Q

what is a major protein source for the host

A

microbial protein

40
Q

does urea contain any E, minerals or vitamins

A

no

41
Q

why might excess urea be bad

A

can overwhelm liver and cause toxicity