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PHYSIOLOGY III > L28: Forestomach digestion > Flashcards

L28: Forestomach digestion Flashcards

1
Q

animals that mainly eat grass are ?

A

grazers

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2
Q

animals that selectively feed on highly digestible material

A

browsers
can live off grass but aren’t ass efficient as grazers

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3
Q

why might browsers have larger parotid glands than grazers

A

parotid gland produces proline-rich proteins that bind and neutralize tannin

browser diets have much more tannin than grazers

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4
Q

what is the main difference in the rumen between browsers & grazers

A

unlike grazers, browsers have no fiber mat or stratification (not layered)

have homogenous rumen content

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5
Q

is this describing a browser or grazer rumen…

high viscosity fluid, separation due to flotation/sedminetation less possible, gas bubbles evenly distributed

A

browser

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6
Q

is this describing a browser or grazer rumen…

low viscosity fluid, separation due to flotation/sedementation & clear separation of gaseous layer

A

grazer

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7
Q

rumen papilla growth is stimulated by _______, so [ _______ ] is highest where microbial activity is highest

A

VFAs
VFA

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8
Q

rumen _____ reflects stratification & location of greatest microbial activity and absorption of VFA

A

papillation

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9
Q

the time that liquid or a food particle spends in the rumen

A

mean retention time (MRT)

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10
Q

in general, is rumen MRT longer for water or food particles

A

food

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11
Q

what is a benefit and disadvantage of a long MRT of food in the rumen

A

(+) improves utilization of cell wall constituents (fiber)
(-) restricts feed intake b/c intake is limited mostly by the capacity of the forestomach

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12
Q

who has an overall shorter MRT, browsers or grazers

A

browsers

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13
Q

why is food particle throughput smaller in browsers than grazers

A

they rely more on plant cell content which is easily fermentable

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14
Q

what is the benefit of higher fluid throughput in grazers

A
  • helps remove waste & make room for new material
  • removes microbes
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15
Q

how does removing waste and microbes stimulate bacterial growth

A

by maintaining appropriate conditions in the rumen which increases microbial yield

this only works if substrate supply is sufficient & balanced N:C ratio

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16
Q

what is quorum sensing

A

bacteria, through small signal molecules called autoinducers, regulate bacterial population density

involves regulation of gene expression of autoinducers to fluctuations in cell-population density

autoinducers increase in [ ] as a function of cell density

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17
Q

what is the function of the omasum?

A
  • absorb water, electrolytes, VFAs, HCO3
  • transport ingesta to abomasum
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18
Q

the _____ of the omasum create a huge increase in SA

A

laminae

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19
Q

the large volume of water coming from a grazers rumen is reabsorbed by the ?

A

omasum; grazers have larger omasums than browsers since they have a higher fluid throughput

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20
Q

why does more water flow through a grazer’s forestomach?

A

helps remove waste and microbial protein and facilitates better fiber fermentation

21
Q

what are the substrates for microbial production of VFAs

A
  • cellulose (Beta linked glucose polymers, insoluble CHOs)
  • starch, glycogen, sugar (hexoses, alpha linked glucose polymers, soluble CHOs)
22
Q

what are the endproducts of VFA fermentation (VFA –> hexose –> ?)

A
  • acetate
  • proprionate
  • butyrate
23
Q

what is the pka of VFAs

A

4.8

24
Q

at a pH of 6.8, most VFAs exist in what form?

A

dissociated form
uses the VFA/HCO3 exchanger for intracellular transport

25
Q

at pHs closer to the pKa of VFAs, how are VFAs absorbed

A

via diffusion ( [ ] gradient)

26
Q

acetate enters the Krebs cycle as ?

A

Acetyl-CoA

27
Q

propionate enters the Krebs cycle as?

A

Succinyl-CoA –> gluconeogenesis

28
Q

buturate gets converted into _______ and then enters the Krebs cycle as _______

A

Beta hydroxybuturate (ketone body) in the rumen epithelium
enters Krebs as Acetyl-CoA

29
Q

the most important gluconeogenic substrate; major source of glucose

A

propionate

30
Q

if VFAs accumulate in the rumen, they lower ?

A

pH; favors microbes producing lactic acid

31
Q

A high amount of _______ generate large amounts of VFAs quickly

A

easily digestible CHOs (beets/apples/grain)

32
Q

how does pH affect microbial growth rate

A

each bacterial species has a pH range w/in which growth is possible; pH optimums

33
Q

explain Rumenoacidosis

A
  • carbohydrate overload leads to increases VFAs and decreased pH
  • lactate production increases, further decreasing pH
34
Q

what are the symptoms of rumenoacidosis

A

unspecific but… variable appetite, decrease in milk production, D+, bloat, reduced rumen motility, increased HR and breathing rate, laminitis

35
Q

glandular digestion of microbial protein in the cow begins in the ?

A

abomasum via abomasal enzymes such as lysozymes

it then continues in the duodenum w/ pancreatic enzymes

36
Q

what do lysozymes do

A

catalyze the hydrolysis of bacterial cell walls

37
Q

how does lysozyme production in ruminants compare to most mammals

A
  • ruminants secrete large amounts of lysozymes in the lumen of the abomasum
  • most mammals produce moderate-high levels of lysozyme in tears and saliva, WBCs and tissue macros
38
Q

T/F: lysozymes are most active at low pH

A

true

39
Q

a measure for estimating how well a particular protein source is used

A

biological value

40
Q

what is the purpose of urea recycling?

A

ruminants recycle urea via saliva into the rumen for usage by bacteria that turn it into microbial protein

41
Q

aquaporins & urea transporter B are involved in ______ in ruminants

A

urea recycling

42
Q

what is the purpose of urea recycling in hindgut fermenters/nonruminants

A

it is a salvage mechanism that improves Nitrogen retention during times of protein deficit

43
Q

what determines the amount of microbial protein that reaches the small intestine

A

the amount of dietary crude protein & metabolic demand

44
Q

what determines the amount of plasma urea in a ruminant

A

the amount of microbial protein that reaches the SI & the presence of excess ammonia

45
Q

where does ammonia get absorbed, where does it get detoxified

A

rumen
detox in liver via urea cycle

46
Q

what causes an accumulation of ruminal ammonia

A

if the rate of ammonia production or ingestion of ammonia exceeds the microbe’s ability to utilize it to form amino acids

47
Q

what is urea poisoning / ammonia toxicosis

A

liver gets overwhelmed by the amount of ammonia, results in elevated blood ammonia levels

accumulation of ruminal ammonia can cause alkaline indigestion if pH exceeds 7.5 –> ruminal contractions inhibited

48
Q

what anatomical structure diverts the flow of milk into the abomaum of a fetus

A

esophageal groove

49
Q

explain rumen drinkers

A

fast drinking (no-little suckling of milk) can cause spill over into the rumen if the esophageal groove is not fully formed

milk ending up in the rumen gets fermented to lactic acid, decreases the pH, causing inflammation of the lining

lining becomes irritated & thickened; damages ability to contract and absorb nutrients

results in: malnutrition, bloat, acidosis, depression, weakness

PHYSIOLOGY III (31 decks)

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