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ANSC 315 > Module 7- Nutrient digestibility > Flashcards

Module 7- Nutrient digestibility Flashcards

1
Q

digestibility

A

proportion of a feed that is not excreted in feces and therefore assumed to be absorbed

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2
Q

what is the major determinant of nutritional value of feeds

A

digestibility

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3
Q

high digestibility = ( ) nutrient retention = ( ) performance

A

high, high

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4
Q

3 ways to measure feed digestibility + example for each

A

1) in vivo
- total fecal collections
- indicator method
2) in situ
- nylon bag
3) in vitro
- tilley & terry method

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5
Q

nylon bag technique

A

feed is contained in nylon bag & placed in rumen

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6
Q

in situ means

A

between in vivo + in vitro

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7
Q

why is an adaptation period required for in vivo digestibility measurement? (3)

A

1) need time for residual feed from previous diet to be totally excreted
- takes several days for ruminants
2) GI tract needs to adapt
3) adapt to new environment

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8
Q

why is a balloon inflated with distilled water in bladder catheter for total urine collection?

A

so catheter stays in place

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9
Q

metabolism crates only use what sex of animal? why?

A

male, urine is diverted into funnel below crate

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10
Q

adaptation period for metabolism stalls vs crates

A

stalls: 4-14
crates: 2-3 days

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11
Q

issues with digestibility harness

A

bags fill up fast & become heavy
- more labour to empty bags frequently

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12
Q

true digestibility is always going to be ( ) than apparent digestibility. why?

A

higher, bc of sloughed off epithelial cells/enzymes
- overestimating proteins in feces

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13
Q

what is the protein in feces? (2)

A

undigested protein from feed & endogenous protein

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14
Q

NDF will always use ( ) digestibility bc no NDF secreted in GI tract

A

true

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15
Q

indirect measurement of digestibility

A

use basal diet digestibility & compare with test ingredient digestibility

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16
Q

associative effects of indirect measurement of digestibility (problem)

A

assumes digestibility of test ingredient stays at that % when mixed with other ingredients

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17
Q

2 problems with total collections

A

1) accurate estimate of feed intake
2) must collect ALL fecal output

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18
Q

measuring digestibility with the indicator method

A

add indicator to feed at low level & measure the concentration in the feces

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19
Q

indicator is often added at (%)

A

0.5

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20
Q

steady state

A

consistent feed intake & fecal output

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21
Q

DM digestibility using indicator/marker =

A

100 - (% indicator in feed) x 100) / (% indicator in feces)

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22
Q

specific nutrient digestibility =

A

100 - (% indicator in feed) x (% nutrient in feces ) x 100 / (% indicator in feces) x (% nutrient in feed)

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23
Q

concentration of indicator in the feces is always going to be ( ) than it is in the feed. why?

A

greater, as feed gets digested = concentrates indicator

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24
Q

7 properties of an ideal indicator or marker

A

1) cannot be digested/absorbed
2) no negative impacts
3) associated with material that it is to mark
4) uniformly excreted in feces each time
5) inexpensive
6) readily available
7) easily detected / easy to measure

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25
Q

2 types of digestibility markers + examples

A

1) internal markers -> already contained in test feed
- lignin
2) external markers -> chemical added to test feed
- chromic oxide

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26
Q

most common external marker used

A

chromic oxide

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27
Q

what 2 methods stimulate rumen fermentation & gastric digestion under controlled environments?

A

in vitro & in situ

28
Q

tilley & terry method

A

done in test tube
1) incubation of rumen fluid
2) 2nd incubation with pepsin

29
Q

why is a buffer needed in the tilley & terry method

A

microorganims in rumen have optimal environment that they can survive in

30
Q

what environment is the tilley & terry method done in? why?

A

anaerobic bc microorganisms are anaerobic

31
Q

purpose of incubating with pepsin in the tilley & terry method

A

mimics what goes on after the rumen

32
Q

IVDMD

A

in vitro dry matter digestibility

33
Q

IVDMD =

A

100% x [(initial dry sample weight - (residue - blank))/ initial dry sample weight

34
Q

tilley & terry method uses what kind of flask

A

blank

35
Q

what does the blank flask contain in the tilley & terry method

A

rumen fluid + buffer

36
Q

why does the tilley & terry method not add test feed to the flask?

A

cannot get rid of residual feed from donor cow rumen fluid

37
Q

advantage & disadvantage of the tilley & terry method

A

advantage: process very large numbers quickly
disadvantage: rumen fluid exposure to atmospheric air can kill microorganisms

38
Q

typical length of incubation in tilley & terry method

A

48 hours, but can be 24 for highly digestible feeds

39
Q

purpose of shaking apparatus in tilley & terry method

A

need rumen fluid & test feed to be continuously mixed

40
Q

nylon bag pore size

A

50 microns -> do not want any feed to escape that is not through digestion

41
Q

how are DM or residues determined in the nylon bag method

A

rinse bags under water & put in oven

42
Q

graph for rate of digestion of feed ingredients for nylon bag method: X vs Y axis

A

X axis: time for DM to disappear from bags
Y axis: % disappeared

43
Q

mobile nylon bag technique

A
  • used to determine mostly forage digestibility
  • mimics digestion in stomach by incubating bags with pepsin & HCI and then incubating into duodenum
44
Q

where is the mobile nylon bag placed inside pigs?

A

proximal duodenum

45
Q

what is it called when you do the nylon bag method in pigs?

A

mobile nylon bag technique

46
Q

effect of fiber on energy digestibility

A

increase in fiber content = decrease digestibility
- mature plants
- reduces ability for enzymes to penetrate cell wall = less digestibility

47
Q

why does lignin decrease digestibility?

A

it binds everything together

48
Q

as plants mature, fiber content will

A

increase

49
Q

effects of feed processing on digestibility

A

improves digestibility bc increases surface area for enzymes to do their work

50
Q

there is a bigger response when you grind ( ) quality feeds compared to ( ) quality feeds

A

lower, higher

51
Q

lower feed conversion =

A

better efficiency bc less feed required for animal to gain weight

52
Q

oat vs wheat : quality

A

oat is lower quality than wheat

53
Q

too small of particle size ( ) digestibility. why?

A

reduces, increased passage rate

54
Q

what feeds can contain trypsin inhibitor, tannins, and glucosinolates

A

trypsin inhibitors: raw soybeans
tannins: faba beans
glucosinolates: rapeseed (canola)

55
Q

phytases in monogastrics vs ruminants on feed digestibility

A

reduces feed digestibility

56
Q

why is phytase added to monogastric diets?

A

to break down phytate to release P

57
Q

phytase improves P digestibility in

A

cereal grains

58
Q

enviropig

A

could digest phytate P

59
Q

what is the major advantage ruminants have with fibre digestibility?

A

presence of microorganisms that can digest cellulose & hemicellulose

60
Q

why do pigs not get a lot out of fiber?

A

bc they do not have a large enough fermentation chamber

61
Q

as animals get older, their ability to digest feed ( ). why?

A

improves, higher expression of enzymes

62
Q

what is the exception to increasing enzyme expression with age?

A

lactase -> it diminishes as animals are weaned

63
Q

high levels of fiber intake will ( ) passage rate and ( ) digestibility

A

increase, decreases

64
Q

why does digestibility decrease in 4x maintenance?

A

bc animal is eating more feed so passage rate increases & reduces digestibility

65
Q

animals exposed to cold weather will have ( ) digestibility. why?

A

decreased, bc higher level of DMI=higher passage rate

66
Q

fiber digestibility ( ) in summer. why?

A

decreases, consuming more water = increases passage rate

ANSC 315 (9 decks)

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