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RUSVM Physiology II > Final Exam GI Physiology: Ruminant Digestion > Flashcards

Final Exam GI Physiology: Ruminant Digestion Flashcards

1
Q

What is the principal distinguishing characteristic of ruminant digestion?

A

Fermentation of ingesta by microbes in the ruminoreticulum

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2
Q

What is fermentation?

A

The anaerobic oxidation of substrate followed by reduction of an organic molecule

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3
Q

Lactate formed from pyruvate is an example of what?

A

Fermentation

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4
Q

Methane formed from CO2 is an example of what?

A

Fermentation

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5
Q

Fermentation of amino acids yields what products?

A

Sulfates and Nitrates

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6
Q

What products are produced when sulfates and nitrates are reduced?

A

H2S
NH3
NH4+

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7
Q

In regards to fermentation of carbohydrates, put the following in order from which ferments fastest to which ferments slowest:
Simple sugars
Starches
Cellulose

A

Simple sugars RAPID
Starches MODERATE
Cellulose SLOW

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8
Q

What are the products of fermentation of simple sugars, starches, and cellulose (carbohydrates)?

A 
CO2
CH4
Lactic Acid
VFAs
Acetic Acid
Proprionic Acid
Butyric Acid
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9
Q

T or F: Microbes can perform oxidation in the absence of oxygen.

A

TRUE

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10
Q

What enzyme is utilized by microbes in the rumen to oxidize pyruvate to acetyl CoA?

A

Pyruvate-ferrodoxin oxidoreductase

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11
Q

What enzyme in the rumen acts on the acetyl CoA produced?

A

Phosphotransacetylase

Adds Pi to Acetyl CoA –> Acetyl-Pi and Coenzyme A

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12
Q

What enzyme in the rumen is used by microbes along with ADP to act on Acetyl-Pi produced earlier?

A

Acetate kinase

Acetyl-Pi + ADP —acetate kinase—> acetic acid + ATP

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13
Q

What are the waste products of carbohydrate fermentation?

A

Volatile Fatty Acids!

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14
Q

How do anaerobic microbes generate ATP?

A

By glycolysis and microbe-enzyme reactions in the rumen

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15
Q

In the rumen/reticulum, what are O2 and CO2 ultimately reduced into?

A

H2O and CH4

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16
Q

The ratio of VFA : Lactic acid is a function of ______ .

A

Diet

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17
Q

A low VFA : Lactic Acid (and therefore low rumen pH) ratio is indicative of what kind of diet?

A

High % of easily digestible carbs

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18
Q

What ruminal pH is considered normal?

A

pH of 6

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19
Q

What is a dietary cause of Ruminal Lactic Acidosis?

A

A low VFA : Lactic Acid ratio (caused by too much easily digestible carbs in diet)

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20
Q

What conditions can Ruminal Lactic Acidosis lead to?

A

Ulceration, pain, going off feed, systemic ketoacidosis

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21
Q

How is protein digested in the rumen?

A

Through microbial digestion and hydrolysis via pancreatic and brush border enzymes

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22
Q

What do microbes do to proteins in the rumen?

A

Hydrolysis of protein –> amino acids

Hydrolysis of amino acids —deamination—> VFA

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23
Q

What is generated as a result of amino acid deamination to VFA?

A

AMMONIA (NH3)

24
Q

What is produced Ammonia utilized for?

A

To make microbial protein

To be converted into urea by the liver

25
Q

What % of protein escapes microbial digestion?

A

50%

26
Q

The 50% of protein that escapes microbial digestion is hydrolyzed in the _______ and _________ via pancreatic and brush border enzymes.

A

Abomasum and Small Intestine

27
Q

Protein hydrolyzed by pancreatic and brush border enzymes yield what products?

A

Small peptides and amino acids

28
Q

Where are dead microbes digested?

A

Abomasum and small intestine

29
Q

Where can urea be found after it is produced by the liver?

A

Urea can diffuse into GI tract lumen

Urea can be secreted by salivary glands

30
Q

What enzyme converts urea into NH3 (ammonia) and CO2?

A

Microbial urease

31
Q

How is produced CO2 utilized?

A

CO2 is used in carboxylase reactions

Ex: Pyruvate —oxaloacetate—> Proprionate

32
Q

What are triacylglycerol and phospholipids hydrolyzed (by microbes) into?

A

Glycerol and FFA

33
Q

Ruminants characteristically have a _______ level of saturated fat.

A

HIGH

34
Q

What is produced FFA used for?

A

Incorporation into chylomicrons

35
Q

What is the fermentation product of glycerol?

A

VFAs! Specifically proprionic acid

36
Q

All VFAs are _______ acids

A

All VFAs are carboxylic acids

37
Q

VFAs constitute what percentage of a ruminant animal’s daily energy requirement?

A

70%

38
Q

VFAs constitute 70% of a ruminant animal’s daily energy requirement. What is the relative percentage of ACETIC ACID?

A

60%

39
Q

VFAs constitute 70% of a ruminant animal’s daily energy requirement. What is the relative percentage of PROPIONIC ACID?

A

25%

40
Q

VFAs constitute 70% of a ruminant animal’s daily energy requirement. What is the relative percentage of BUTYRIC ACID?

A

15%

41
Q

VFA’s are largely __________ at normal ruminal pH of 6.

A

NON DISSOCIATED

42
Q

What is the fate of Acetic Acid (a VFA)?

A

Acetic Acid is converted into Acetyl CoA in muscle and fat.

43
Q

What is the fate of Propionic Acid (a VFA)?

A

Propionic Acid is REMOVED from plasma by the LIVER

44
Q

What is the fate of Butyric Acid (a VFA)?

A

Converted to ketone bodies, acetyl CoA, or removed by the liver

45
Q

Is Lactate a volatile fatty acid?

A

NO. Lactate is NOT a VFA

46
Q

If VFAs constitute 70% of a ruminant’s daily energy requirement, what makes up the remaining 30%?

A

LACTATE

47
Q

What happens to Lactate in circulation?

A

Lactate is REMOVED from plasma by the LIVER (just like propionic and butyric acids)

48
Q

What happens to Lactate in the liver?

A

Lactate is converted to PYRUVATE in the liver

49
Q

What happens to Propionate in the liver?

A

Propionate is converted to SUCCINYL COA in the liver

50
Q

What happens to Butyrate in the liver?

A

Butyrate is converted to 2 Acetyl CoAs in liver mitochondrion

51
Q

What does an increased concentration of Acetyl CoA in the liver inhibit?

A

Increased Acetyl CoA in the liver inhibits PDH (pyruvate dehydrogenase) Complex and increases activity of pyruvate carboxylase

52
Q

What is the function of pyruvate carboxylase?

A

Converts pyruvate into oxaloacetate

53
Q

Which 2 VFA’s are converted to TCA intermediates and then Glucose via gluconeogenesis?

A

Lactate and Propionate

54
Q

Where does the energy come from that supplies the process of turning lactate and propionate into glucose?

A

The oxidation of Butyrate

55
Q

Almost ALL carbohydrates ingested by ruminants is ________.

A

FERMENTED

56
Q

Almost NO glucose is ________ by the GI Tract of ruminants.

A

no glucose absorbed

RUSVM Physiology II (17 decks)

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