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RUSVM Physiology 2 > Ruminant GI Physiology > Flashcards

Ruminant GI Physiology Flashcards

1
Q

ruminants

A

animals that regurgitate and remasticate their food

2 suborders: ruminantia and tylopoda

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2
Q

fermentative digestion

A

occurs in specialized compartments localized before the stomach or after the stomach and small intestine

microbes responsible for fermentative digestion are bacteria, fungi, and protozoa

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3
Q

ruminal ecosystem

A

protozoa ingest large numbers of bacteria and hold bacterial number in check

protozoa may also play a role in starch and protein digestion, they prolong the digestion of these substances and protect them from bacterial action

the waste products produced by one species serve as a substrate for another

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4
Q

ruminal environment

A

substrate availability: food intake is regulated by volume, structure, energy, palatability

temperature: about 0.5-1 degree above the body temperature
fluids: water and saliva

pH: 5.5-7

osmolarity: 260 bis>400 mOsm/l

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5
Q

plant cell walls

A

important substrates for fermentative digestion and significant nutrient source for many species

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6
Q

carbohydrates

A

cellulose, hemicellulose, pectin, lignin

all but lignin are not available for absorption by the animal, they are further metabolized by the microbes

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7
Q

ruminal layers

A

gas

fiber mat

intermediate zone

liquid zone

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8
Q

products of fermentative digestion

A

volatile fatty acids

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9
Q

major VFAs

A

acetate, propionate, butyrate

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10
Q

what is the only VFA that can be used for gluconeogenesis?

A

propionate

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11
Q

how are proteins broken down?

A

deamination

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12
Q

why are proteins vulnerable to fermentation?

A

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

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13
Q

what do amino acids contribute to?

A

synthesis of microbial protein

metabolized to VFA and ammonia

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14
Q

deamination

A

amino acid—-> NH3 + carbon skeleton

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15
Q

why do ruminants depend on microbial proteins to meet their own needs?

A

because almost all dietary protein is fermented in the rumen

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16
Q

how can protein be produced in the rumen?

A

protein and nonprotein sources such as ammonia, nitrates, and urea

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17
Q

urea recycling

A

urea is nitrogen waste product of protein catabolism

2 sources in the ruminant: urea coming from deamination of endogenous amino acids excreted in the liver and nitrogen absorbed as ammonia from the rumen

a portion of the urea which is excreted into the rumen can be resynthesized into protein that will contribute eventually to the amino acid needs of the host

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18
Q

do microorganisms produce the necessary enzymes for lipid digestion? if so what are they

A

yes, lipases and phospholipases

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19
Q

triglycerides

A

major lipid type found in cereal grains, oilseeds, animal fats, and byproduct feeds. also present in milk

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20
Q

glycolipids

A

major lipid type found in forages

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21
Q

phospholipids

A

minor component of most feeds. form the cell membrane of all animal cells, and the surface of milk fat globules. important in fat digestion in the small intestine of cows

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22
Q

free fatty acids

A

minor component of dairy feeds, but major component of certain fat supplements

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23
Q

how are fats hydrolyzed?

A

by microbial lipases

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24
Q

what does fat hydrolysis result in?

A

glycerol and sugars and free fatty acids

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25
Q

what vitamins do microbes synthesize?

A

Vitamin C, K, B, thymin, cobalamin

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26
Q

absorption in the rumen

A

2 main mechanisms depending on the ionization state of the VFA

ionized need a carrier, non-ionized can diffuse through the apical membrane

27
Q

implication in rumen acidosis

A

fast fermentable carbs lead to an increase in VFA production–> pH in the rumen drops

ionization grade of VFA depends on the pH of the rumen

under normal conditions rumen pH is 5.5-7

pK of VFA is 4.8

non-ionized VFA can just diffuse so they will rapidly enter into the rumen epithelium

intracellularly, the pH is higher and the VFA can dissociate into Ac- and H+ which represents an additional risk for the cell

the acidic pH in the rumen stimulates proliferation of lactate producing bacteria–> exacerbation of the acidosis

28
Q

absorption of sodium, potassium, and chloride in the rumen

A

sodium: electrogenic transport via sodium channels, electroneutral transport via sodium proton exchanger, basolateral sodium potassium ATPase

Chloride: Cl-/HCO3- exchanger, maybe a basolateral exchanger

potassium: apical and basolateral channels, high luminal potassium concentration so transepithelial potential difference

29
Q

absorption of calcium and magnesium in the rumen

A

magnesium: electrogenic transport via magnesium channel, affected in the presence of high potassium concentrations–> pastures grass tetany
calcium: reabsorption not fully understood, but probably electroneutral exchange and basolateral sodium calcium exchanger and Ca ATPase

30
Q

what are the forestomachs lined with?

A

stratified squamous epithelium

31
Q

absorption in the omasum

A

concentration of the ingesta

SCFA absorption

Na+ and Cl- absorption

HCO3- reabsorption

32
Q

the fate of VFAs in the ruminant

A

propionate–> liver–> glucose

acetate and butyrate–> all tissues–> energy

acetate–> adipose tissue–> fatty acids

33
Q

requirements for proper fermentation

A

substrate for fermentation

temperature near 37

osmolality of 300mOsm

negative oxidative reduction potential

indigestible waste must be removed

regeneration of microbes

buffer substances

34
Q

primary contractions

A

the bolus enters the rumen and remains suspended in the area near the cardia

biphasic contraction of the reticulum
first contraction is weak
second is forceful, nearly obliterating the lumen of the reticulum–> bigger particles will be pushed into the dorsal sac

caudal moving contraction of the dorsal sac moves ingesta further back into the dorsal sac

cranial moving contraction of the dorsal sac mized the ingesta. this ingesta is now under bacterial fermentation which produces a gas. this gas accumulates in the dorsal sac

the smaller particles decant into the ventral sac

contraction of the ventral sac separates big and small material; small material goes over the cranial pillar into the cranial sac

contraction of the cranial sac which further separates material into big and small

a new cycle starts, the reticulum contracts, the reticulo-omasal orifice relaxes and small particles are forced through the opening into the omasum

35
Q

function of primary contractions

A

reduce particle size

36
Q

secondary contractions

A

function is to force gas toward the cranial portion of the rumen

37
Q

how many contractions per minute

A

1-3, more frequent during eating and disappear during sleep

rate and strength depend on character of the diet

38
Q

what are the main gases produced during rumination?

A

carbon dioxide and methane

39
Q

eructation frequency

A

1/min

40
Q

eructation center

A

localized in the medulla and receives afferent fibers form mechanoreceptors placed in the dorsal sac of the rumen

41
Q

tympanism

A

bloating

occurs when the eructation mechanism fails

42
Q

legume bloat

A

when cattle feed on lush, rapidly growing alfalfa or clover pastures

gas becomes trapped in tiny bubbles and the normal free gas bubble cannot accumulate on top of the dorsal sac of the rumen to the presence of gas is not detectable by the mechanoreceptors

43
Q

ruminant ketosis

A

occur most frequently in high producing dairy cows, usually within 6 weeks of calving or in late gestation

acetate and butyrate enter the TCA cycle as acetyl CoA

if there is not enough oxaloacetate or if there is an excess of acetyl CoA, it accumulates and gets degraded to ketone bodies

44
Q

control of reticulorumen motility

A

ENS and vagus nerve

control center is in the brain stem as the dorsal vagal nucleus

stretch receptors and chemoreceptors monitor distention, consistency of the ingesta, pH, VFA concentration, ionic strength

45
Q

esophageal groove

A

gutter like invagination traversing the wall of the reticulum from the cardia to the reticulo-omasal orifice

diverts milk away from the developing rumen and passes it directly to the abomasum

closure is a relfex action

46
Q

hindgut fermentation

A

horses rely on fermentation in the colon to cover their energy needs

47
Q

substrates for hindgut fermentation

A

structural and nonstructural carbohydrates as well as proteins

fermentation products are VFA and absorption mechanisms are similar to that observed in ruminants

48
Q

conditions for maintaining fermentation

A

substrate supply

control of pH

osmolality

anaerobiosis

retention of fermenting material

removal of waste product and residue

49
Q

predominant motility patterns in ventral colon

A

haustral segmentations, propulsive peristalsis, retropulsive peristalsis

50
Q

the principal end products of dietary carbohydrates in ruminants are?

A. triglycerides
B. glucose
C. amino acids
D. VFAs

A

D

51
Q

which of the following is a component of rumination?

A. vomiting
B. eructation
C. flatulence
D. regurgitation

A

D

52
Q

the 2 major motility patterns observed in the rumen are

A. peristaltic and antiperistaltic waves
B. segmentation and propulsive contractions
C. mixing and eructation contractions

A

C

53
Q

deglutition, eructation, and regurgitation can be observed on the left side of a cow

A. true
B. false

A

A

54
Q

comparing forestomach versus hindgut fermentation which is true?

A. the microbial populations are different but the products are the same
B. microbial populations are the same but the products are different
C. both microbial populations and products are similar

A

C

55
Q

How do ruminants get glucose needed for energy?

A

all glucose available to ruminants originates from gluconeogenesis, the most important precursor being propionate

56
Q

succinate

A

4 carbon intermediate that can lead to the formation of oxaloacetate which is the entry metabolite from gluconeogenesis

57
Q

special considerations for glucose homeostasis in ruminants

A

ruminants exist in a constant state of potential glucose deficiency

gluconeogenesis covers most of the glucose needs

insulin levels are regulated by the concentration of SCFAs

all the glucose available to ruminants originates from gluconeogenesis. the most important precursor of glucose in ruminants is the VFA propionate

almost all propionate absorbed from the rumen is extracted from the portal blood by the liver and never enters the systemic circulation

ruminants also efficiently conserve glucose. in ruminants, fatty acids are synthesized only in adipose tissues using acetate as a precursor molecule and never glucose

in high producing dairy cows, nearly all the glucose they produce goes to lactose; the remaining tissues function on alternative fuels

58
Q

concerning protein fermentation in the rumen, which of the following is correct?

A. endopeptidases are of host’s origin
B. peptides and amino acids can be used by microbes to synthesize microbial protein
C. both are right

A

B

59
Q

which of the following vitamins is not synthesized by ruminal microbes?

A. vitamin B12
B. vitamin K
C. vitamin D
D. vitamin C

A

C

60
Q

which of the following concerning ruminal motility is true?

A. biphasic contractions of the reticulum occur in the beginning of the cycle
B. the function of primary contractions is to reduce particle size
C. the function of secondary contractions is to force has toward the cranial portion of the rumen
D. all of the above is correct

A

D

61
Q

eructation is activated by mechanoreceptors located in the ventral sac of the rumen

A. true
B. false

A

B

62
Q

bloat in cattle is caused by

A. an increase in the volume of gas produced
B. a failure of the eructation mechanism

A

B

63
Q

regurgitation occurs before the regular biphasic contraction of the reticulum

A. true
B. false

A

A

RUSVM Physiology 2 (3 decks)

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