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ANSC 315 > Module 6- Nutrients & chemical analysis > Flashcards

Module 6- Nutrients & chemical analysis Flashcards

1
Q

what kg of composite sample so feed should you take

A

1-2kg

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2
Q

nutrient content expressed on a DM basis is always ( ) when expressed on as-fed basis

A

greater

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3
Q

proximate analysis

A

series of analytical procedures that partitions the feed into 6 fractions

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4
Q

6 fractions of proximate analysis

A

1) moisture or DM
2) Ash (minerals)
3) CP
4) EE
5) crude fiber
6) nitrogen free extract

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5
Q

crude protein

A

represents nitrogenous compounds contained in the feed

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6
Q

crude fiber

A

represents cell wall & less digestible components
- cellulose
- hemicelullose
- lignin

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7
Q

T or F: crude fiber is measured

A

F

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8
Q

purpose of moisture in a diet

A

provides texture

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9
Q

2 things that will occur with too much moisture in the feed

A

1) reduction in DMI
2) reduce storage life

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10
Q

moisture/DM determination procedure

A

drying feed to a constant weight by putting in oven at 55 C

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11
Q

DM content of a feed =

A

weight of dry feed / weight of wet feed x 100

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12
Q

4 methods of DM analysis

A

1) forced air oven
2) moisture meter
3) freeze drying
4) near-infrared reflectance spectroscopy

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13
Q

what is the most accurate DM analysis method? why?

A

freeze drying, do not lose any volatile materials

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14
Q

2 volatile materials in feed

A

ammonia + VFAs

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15
Q

1 disadvantage to oven drying of DM analysis

A

underestimate how much DM bc of ammonia & VFA loss from heat

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16
Q

koster moisture tester

A

small portable electric drying unit, used on farms

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17
Q

moisture tracker device

A

hand held NIR scanning device for silage

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18
Q

ash determination principle

A

completely combust sample in muffle furnace at 500-600C = residue left is the mineral content of feed

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19
Q

% ash =

A

weight of residue / weight of feed sample x 100

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20
Q

disadvantage to ash determination

A

lose iodine & selenium at high temps = underestimate ash content

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21
Q

wet ashing procedure

A

use concentrated percholric acid, do not any lose minerals

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22
Q

how is crude protein determined

A

Kjeldahl distillation

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23
Q

Kjeldahl distillation procedure

A

measures total N content of test feed & uses it to estimate CP content

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24
Q

during crude protein determination, all N is converted to

A

ammonium sulfate

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25
Q

Kjeldahl factor

A

6.25

26
Q

CP % =

A

N x 6.25

27
Q

macro-kjeldahl apparatus disadvantage

A

time consuming, only 1-2 batches / day

28
Q

titration

A

titrating boric acid with HCI

29
Q

leco method for N analysis

A

combust sample in O2 rich environment

30
Q

why is the conversion factor for CP 6.25?

A

assuming proteins contain 16% N
molecular weight of N / total molecular weight x 100 + 16%
100/16 = 6.25

31
Q

why is it called crude protein

A

it is a crude estimate of how much protein there is
- contains other N compounds not in form of AA

32
Q

Kjeldahl factor is actually

A

7.74

33
Q

kjeldahl factor use for mixed feeds vs individual feeds

A

mixed- 6.25
individual- use specific kjeldahl factors for specific feeds

34
Q

2 limitations to kjeldahl CP determination

A

1) assumes all protein contains 16% N
2) assumes all n comes from protein

35
Q

why is CP a bigger deal in monogastrics vs ruminants

A

monogastrics need AA from true protein in the diet, while ruminants can use any source of N

36
Q

principle of CP analysis

A

converting all N contained in the feed to ammonia and then use total content of N to calculate CP by N x 6.25%

37
Q

urea as a NPN source contains ( ) %

A

45

38
Q

2 limitations to using urea in the diet

A

1) urea is not very palatable
2) toxicity

39
Q

principle of ether extract/crude fat determination

A

extract feed sample with diethyl ether to remove anything soluble
- anything soluble is lipid

40
Q

diethyl extract is a

A

organic solvent

41
Q

%EE =

A

weight of residue / weight of original sample X 100

42
Q

soxhlet extractor

A

heat sample to 35 C, vapor released is the ether, use organic solvent to extract

43
Q

2 main energy sources in ether extract

A

triglycerides & free FA

44
Q

why is it called crude fat

A

inclusions of resins & waxes

45
Q

2 problems with ether extract determination

A

1) EE fraction is assumed to have high E content
2) if EE fraction contains high % of waxes & resins = overestimate E content

46
Q

% CF =

A

weight of residue / weight of feed sample x 100

47
Q

2 issues with crude fiber determination

A

1) some cellulose, hemicellulose & lignin ends up in NFE = underestimate CF
2) not highly repeatable

48
Q

NFE

A

nitrogen free extract, contains digestible carb fraction (starch & sugars)

49
Q

T or F: there is a chemical analysis for NFE

A

F

50
Q

NFE =

A

100- (%CP + % EE + % CF + % ash + %H2O)

51
Q

T or F: NFE is used today for diet formulations

A

F

52
Q

T or F: TDN will not work without proximate analysis

A

T

53
Q

3 disadvantages of proximate analysis

A

1) does not define individual nutrients -> ash components
2) time-consuming
3) no indication of digestibility

54
Q

what replaced crude fiber analysis?

A

detergent extraction system

55
Q

detergent extraction system

A

partitions fiber components into soluble & insoluble carbs
- NDF & ADF

56
Q

benefit of detergent extraction system

A

better indication of fiber content of feed

57
Q

cell wall components (ADF vs NDF)

A

cell wall: cellulose, hemicellulose, lignin
ADF= cellulose & lignin
NDF = hemicellulose + cellulose + lignin

58
Q

how does the detergent extraction system work?

A

1) digest forage with neutral detergent solution
2) extract cell contents from NDF
3) digest NDF with acid detergent
4) digest ADF with 72% sulfuric acid to get cellulose & lignin

59
Q

what does sulphuric acid do in detergent extraction

A

dissolves cellulose, lignin is left

60
Q

example of a neutral detergent solution vs acid detergent solution

A

neutral- EDTA
acid- H2SO4

61
Q

near infrared reflectance spectroscopy (NIRS)

A

uses 5g sample
absorption of light by feed ingredient

62
Q

NIR uses ( ) range of visible light

A

outside
700-2500nm

ANSC 315 (9 decks)

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