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Physiology 2 > 2. GI Part 10 > Flashcards

2. GI Part 10 Flashcards

1
Q

why are proteins vulnerable to fermentation

A

they are made of carbon compounds that cna be further reduced to provide energy for anaerobic microbes

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2
Q

what do microbes produce and what do they form as end products
where are these end products absorbed

A

microbes produce endopeptidases that form short chain peptides as end products

these peptides are absorbed into microbial cell bodies

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3
Q

what are peptides used for in the microbial cell

A

used to form microbial protein or can be further digested for energy production via VFA pathway

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4
Q

describe protein metabolism by rumen microbes

A

proteases on microbe surface generate peptides from proteins

intracellularly, peptides are hydrolyzed to amino acids

amino acids contributes to synthesis of microbial protein and synthesis of VFA and ammonia

amino acids are also synthesized intracellularly from NH3 and VFA

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5
Q

what must happen for an amino acid to enter VFA pathway

A

the amino acid must deaminate

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6
Q

what happens to amino acid when it is deaminated

A

amino acid –> NH3 + carbon skeleton

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7
Q

can carbon structures of all amino acids be directly used for VFA synthesis

A

most can

exception – BCAA

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8
Q

valine + 2 H2O –>

A

isobutyrate + NH3 + CO2

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9
Q

leucine + 2 H2O –>

A

isovalerate + NH3 + CO2

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10
Q

isoleucine + 2 H2O –>

A

2-methylbutyrate + NH3 + CO2

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11
Q

what does the ruminant depend on to meet its needs

A

microbial protein – because almost all dietary protein is fermented in the rumen

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12
Q

what are the 2 options for ruminants to meet their protein needs

A
  1. microbes washed out of the rumen –> microbial protein reaching the abomasum and the small intestine
  2. protein can be produced in the rumen from protein and non protein sources like ammonia, nitrates, urea
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13
Q

what is urea

A

the nitrogen waste product of protein catabolism

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14
Q

what are the 2 sources that urea is synthesized from in the liver

A
  1. urea coming from deamination of endogenous amino acids

2. nitrogen absorbed as ammonia from the rumen by rumen epithelium

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15
Q

where is urea excreted in monogastric animals

where in ruminants

A

monogastric – kidney

ruminants – kidney, rumen

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16
Q

what happens to some of the urea that reaches the rumen

what conditions does this happen under

A

it can be resynthesized into protein that will contribute to amino acid needs of host animal

under conditions of low dietary protein – conserve nitrogen

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17
Q

are fats and lipids common in cow diets

A

no

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18
Q

are fats common plants

what is excerption

A

no <5% dry matter

exception is oilseeds

19
Q

what enzymes do microbes produces for lipid digestion

A

lipases

phospholipases

20
Q

what kind of fat is in cattle diets

A

PUFA

21
Q

where are triglycerides found

A 
cereal grains
oilseeds
animal fats
byproduct feeds
milk (milk fat)
22
Q

where are glycolipids found

A

forages

23
Q

where are phospholipids found

A

minor component of most feeds

form cell membrane of all animal cells and surface of milk fat globules

important in fat digestion in small intestine of cows

24
Q

where are FFA found

A

minor component in dairy feeds

major component of certain fat supplements

25
Q

what results from fat being hydrolyzed by microbial lipases

what do they go on to make

A

glycerol, sugars –> VFA

FFA –> hydrogenation (biohydrogenation)

26
Q

where do FA synthesized in rumen go

A

pass to abomasum and small intestine for absorption

27
Q

what is the ruminant acetic/propionic/butyric acid concentration ratio for

high forage diets
high grain diets

A

high forage diets – 70:20:10

high grain diets – 60:30:10

28
Q

is total acetate higher in high grain or high forage diets

A

percentage of acetate is lower in high starch diet (high grain), the total amount is considerably greater than the high fiber diet – more total VFA produced

29
Q

what vitamins do microbes synthesize

A

C
K
B – B1 (thiamin), B12 (cobalamin)

30
Q

when do you see a thiamin deficiency

A

after a sudden change of feed form roughage to concentrate

31
Q

when do you see a cobalamin deficiency

A

cobalt poor soils

using diets with too much grain

32
Q

young ruminants and microbial vitamin synthesis

A

relatively small fermentative activity in young ruminants – cannot synthesize vitamins and need them in diet

33
Q

what are the 2 main mechanisms of VFA absorption in the rumen epithelium

A
  1. ionized VFA (Ac-) –> cannot diffuse, need a carrier (HCO3-/Ac- antiport)
  2. non ionized (HAc) –> lipophilic and can diffuse through apical membrane
34
Q

how does rumen acidosis occur

A

fast fermentable carbs (starch rich diet) leads to increase in VFA production –> pH in rumen gets more acidic (lower)

35
Q

what does the pKa indicate

what is pKa of VFA

A

the pH at which a substance is 50% ionized and 50% non ionized

pKa of VFA – 4.8

36
Q

what does the acidic pH of the rumen stimulate

A

proliferation of lactate producing bacteria –> exacerbation of the acidosis

37
Q

describe absorption of chloride in the rumen

A
  1. Cl-/HCO3- exchanger

2. basolateral channel (not fully identified)

38
Q

describe potassium absorption in the rumen

A
  1. apical and basolateral channels

2. high luminal K+ concentration (transepithelial potential difference)

39
Q

describe absorption of magnesium in the rumen

A
  1. electrogenic transport – Mg2+ channel (dependent on potential difference between apical/basolateral side)
40
Q

what is magnesium absorption in the rumen affected by

A

affected in the presence of high K+ concentrations (young pastures or potassium fertilized pastures) – leads to pasture grass tetany

41
Q

clinical signs of pasture grass tetany

A 
irritability
msucle twitching
staring
incoordination
staggering
collapse
thrashing
head thrown back
coma
death
42
Q

describe the absorption of calcium in the rumen

A

reabsorption not fully understood

  1. probably electroneutral (Ca/H exchanger, not fully understood)
  2. basolateral Na/Ca exchanger and Ca ATPase
43
Q

describe the omasum

A

comprised of muscular folds (leaves) that project form the greater curvature into the lumen

canal connects the reticulum with the abomasum

44
Q

functions of the omasum (4)

A
  1. concentration of ingesta (absorption of water)
  2. SCFA (VFA) absorption (diffusion more relevant here)
  3. Na+ and Cl- absorption
  4. HCO3- reabsorption

Physiology 2 (11 decks)

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