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Digestion and Metabolism - Wk 2 > fermentative digestion > Flashcards

fermentative digestion Flashcards

1
Q

what is the most renewable source of energy

A

biomass

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2
Q

what complex in plants is irresistible for breakdown

A

ligno-cellulose complex

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3
Q

how is cellulose linked

A

B1-4 linkage - crystalline structure

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4
Q

what is loosely bound to cellulose

A

hemicellulose

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5
Q

is lignin a carbohydrate

A

no - but it has a phenyl-propane base

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6
Q

what has the ability to unlock covalent linkages (expose) carbs followed by hydrolysis - fermentation

A

microbes

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7
Q

what does colonization by microbes in the digestive tract do

A

essential to exploid the fermentative capacity of mictobes

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8
Q

why do microbes derive energy and nutrients during fermentation

A

to grow

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9
Q

symbiosis

A

mutual benefit between herbiborous host and microbes

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10
Q

what are the 6 suitable conditions for fermentatibe digestion

A
  • reservoir to house microbes in the digestive tract
  • anaerobic environment
  • pH range slighly acid to neutral ((>5.3) 6-7)
  • dietary factors
  • passage rates
  • utilization of by-products and absorption of end products
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11
Q

what is GI modification

A

a region of GI tract enlarged to store food and allow microbiota to colonize and facilitate fermentation

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12
Q

describe hindgut modification in rabbits

A

caecum is modified to carry microbes that help in fiber digestion

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13
Q

what kind of feed is required for rabbits

A

high quality fiber

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14
Q

why do rabbits practice coprophagy

A
  • feces is nutritious and shed at night
  • recycle nutrients - microbial protein
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15
Q

describe hindgut ferementation in horses

A

caecum and colon are modified to carry microbes that help in fiber digestion

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16
Q

where are grains, proteins, and fats digested in horses

A

SI

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17
Q

what are the major fiber sources that are fermented in the caecum-colon in horses

A

pasture/hay

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18
Q

horses at ____ can meet their needs from microbial fermentation

A

maintenance

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19
Q

rumen and hindgut bacteria are strict __

A

anaerobes

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20
Q

why is the redox potential negative

A

electrons are better at exchanging when the system is in a reduced state

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21
Q

what does fermentation produce

A

metabolic hydrogen

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22
Q

what state is the GI in when there is more fiber in the diet

A

more reduced state

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23
Q

what two things happen when oxygen is introduced in feed and water

A
  • diffuse across rumen and hindgut wall
  • used by facultative anaerobes
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24
Q

what is an optimal pH for microbial growth

A

6 to 7

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25
Q

what is pH regulated by

A
  • absorption of VFA
  • buffers (bicarbonate and phosphate in rumen)
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26
Q

what pH of equines and cows cause significant GI and metabolic problems

A

<6; <5.4

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27
Q

what is the role of saliva in fermentation

ruminants

A
  • 100-150 L/day
  • lubrication
  • buffering - NaHCO3
  • fluid for rumen fermentation
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28
Q

what is the role of saliva in fermentation

equine

A
  • 35-40 L/day
  • flow associated with chewing
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29
Q

what are the feed intake patterns of cows

A
  • meal based eaters
  • multiple meals per day total eating time 2-3 hours with 7-12 hrs ruminating
  • process feed slowly
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30
Q

what are the feed intake patterns of equines

A
  • trickle feeders
  • 16-18 hrs a day eating to maintain a full stomach and constant flow through GI tract
  • process feed more rapidly - higher passage rates than foregut fermenters
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31
Q

fiber digestibility is higher in ____ fermenters than ____fermenters

A

foregut; hindgut

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32
Q

where is starch and protein digested in cows and equines

A

rumen; small intestine

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32
Q

what determines how much of feed is digested

A

degradation/passage and site of digestion

33
Q

what is the microbiome comprised of

A

microbes, their genomes, and interactions with host/environment

34
Q

what are the 4 types of microbes

A
  • bacteria
  • fungi
  • archaea
  • protozoa
35
Q

what is the predominant microbe in the rumen

A

bacteria

36
Q

what is bacteria present as

A

a fiber adherent, planktonic and epimural

37
Q

what does bacteria play a key role in

A

fiber, starch , oligo- and monosaccharides fermentation, protein and lipid digestion

38
Q

how is bacteria nomenclature based on

A

substrate

39
Q

protozoa are only ____ and what are the two groups

A

ciliates; holotrichs and oligotrichs

40
Q

what is the role of rumen protozoa

A
  • strong assco. with bacteria and archaea
  • predate on bacteria/methanogens - bateria turnover
  • participate in fiber, starch, oligo- and monosaccharide fermentation, protein and lipid digestion
41
Q

what are rumen anaerobic fungi

A
  • important in ruminants in developing areas
  • free swiming flagellated zoospores attach to plant particles and relate to carb digestion
42
Q

what is the role of rumen archaea

A

not involved in feed digestion but are hydrogen scavengers and naturally form methane

43
Q

what are the three pathways that methane is formed

A
  • hydrogenotrophic methanogens
  • methylotrophic methanogens
  • aceticlastic methanogens
44
Q

what are the nutritional requirements of microbes

A
  • CO2
  • Energy - ATP released during fermentation
  • Nitrogen
  • minerals
45
Q

what do passage rates of feed depend on

A
  • quality of feed
  • feed intake
  • feed characteristics
  • digestion rates
  • host
46
Q

what is carb fermentation composed of

A
  • neutral detergent fiber (NDF)
  • non fiber carbohydrats
47
Q

what are slowly fermented carbs

A

cellulose and hemicellulose

48
Q

what are rapid fermended carbs

A

starch and pectin

49
Q

what do high forage rations have

A

higher NDF and therefore a controlled rate of fermentation

50
Q

what is a prerequisite for digestion of NDF

A

colonization of microbes to feed particles

51
Q

how much of cellulose digestion occurs in the rumen

A

90%

52
Q

what are the two stages of fiber digestion

A
  1. microbial attachment (colonization)
    - slow process
    - specific and non-specific binding
  2. hydrolysis - enzymatic
    - endoenzymes
    - exoenzymes
    - multi-enzyme complexes
53
Q

more fiber in the diet leads to …..

VFA

A

more acetate and butyrate

54
Q

more starch/grain in the diet lead to

VFA

A

propionate

55
Q

runaway fermentation can lead to accumulation of

A

lactate

56
Q

more hydrogen in the diet leads to

A

more methane

57
Q

what are the two ways energy is lost

energy efficiencies

A

CH4 (16%) and heat of fermentation (6%)

58
Q

how are VFA absorbed

A
  • rumen papillae
  • development senensitive to grain in diet (butryate stimulates development)
  • by diffusion
  • removes large am. of acid each day
59
Q

what is acetate important for

A

precursor for milk fat

60
Q

what is propionate important for

A

determinant of milk volume
gluconeogenic

61
Q

what is butryate important for

A

stimulates rumen development and papillae length

62
Q

how are carbs digested in equines

A
  • balance of forage and grain
  • forages fermented in caecum and colon
  • starch and protein in SI
  • if too much grain - colic, diarrhea or laminitis
  • VFA provite immediate energy
63
Q

microbes need protein in what form

A

nitrogen for growth (true protein and NPN, recycled microbia protein, endogenous N)

64
Q

microbes prefer to utilize N from ….

A

ammonia and all N sources are converted to ammonia

65
Q

what is proteolysis

A
  • rapidly convert N sources to ammonia
  • most bacteria are proteolytic
  • beneficial to microbes but not to host
66
Q

what is microbial protein synthesis

A
  • N source from ammonia forms the building block for microbial protein formation
  • need fermentable carbs to supply ATP
  • beneficial to microbes and host
67
Q

where does microbial synthesis occur

types of fermenters

A

foregut and hindgut fermenters

68
Q

is there a need for dierary supplementation of lipids

A

no, microbes synthesize their own fatty acids - present as complex lipids

69
Q

microbes cannot tolerate more than ____ in dietary lipids

A

3%

70
Q

lipolysis

A

complex lipids are hydrolyzed to free fatty acids and glycerol by lipolytic bacteria

71
Q

what is glycerol is converted to

A

VFA

72
Q

what is biohydrogenation

A

conversion of unsaturated FA to saturated FA resulting in the formation of several isomers - bioactive fats

73
Q

cis-9, trans 11 CLA

A

most abundant FA in milk

74
Q

trans-10, cis-12 CLA

A

interferes with milk fat synthesis

75
Q

what do increasing lipid concentrations increase

A

bacteria that participate in normal BH

76
Q

what are the predisposing factors of disruptions in fermentative digestion

A
  • excessive fermentation of starch
  • low pH in rumen or cecum
  • production of amines
  • production of endotoxins
  • laminitis, rumen parakeratosus, liver abscesses, lung abcesses
  • laminitis and colic
77
Q

what is SARA

A
  • well organized digestive disorder in high producing dairy cows resulting in economic losses to dairy herds
  • abrupt chnages in diet, increasing grain, inadequate fiber, fine particle size
78
Q

what happens to the ruminal pH in SARA

A

drops to <5.5 and lactic acid accumulates

79
Q

describe colic in horses

A
  • abdominal pain and is the consequence of all forms of GI disease or problems
  • 10-11% of horses suffer
80
Q

what are the dietary of factors of colic

A

high grain, low fiber, abrupt feed changes, moldy feeds
- factors known to cause disturbances in hindgut microb pop.

Digestion and Metabolism - Wk 2 (5 decks)

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