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Animal Nutrition & Metabolism > Analysis of Feedstuff > Flashcards

Analysis of Feedstuff Flashcards

1
Q

Nutrient

A

Chemical element in the diet that is required for normal reproduction, growth, lactation, or maintenance of life processes

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2
Q

Analytical standard

A

A purified, known material or solution made from an analyte that is used in an assay and against which all sample results are compared to

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3
Q

Gravimetric analysis

A

Technique through which the amount of an analyte can be determined through the measurement of mass

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4
Q

What are the 2 general types of feed assays

A 
Chemical analyses (wet chemistry)
Near infrared (NIR) reflectance spectroscopy
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5
Q

What are 3 examples of chemical analyses

A

Gravimetric, spectrophotometric, chromatographic

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6
Q

What are 2 subdivisions of chemical analysis

A

Empirical fractions and specific analytes

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7
Q

Empirical fractions are defined by

A

The “fraction” or “extract” being measured

Often a mixture of compounds

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8
Q

Empirical assays tend to be…

A

Gravimetric (no analytical standard that represents a pure compound)

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9
Q

Empirical assays must be run using…

A

Standardized methods

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10
Q

What are the two main organizations responsible for the standardization of feed analysis

A

Association of Analytic Chemists (AOAC)

National Forage Testing Association

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11
Q

Specific analytes measure…

A

Specific, identifiable compounds

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12
Q

What are used as standards in specific analytes

A

Purified analytes

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13
Q

What are 3 types of chemical analysis that specific analytes can be measured by

A

Colorimetric, chromatographic, or spectroscopic

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14
Q

What is a proximate analysis

A

A combinator of analytical procedure, outdated, many limitations from a nutritional standpoint, still used by legislations for the declaration of the composition of foods in many countries

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15
Q

The proximate analysis divides the food into what 6 components

A

Moisture, crude protein, crude fat, crude fiber, ash, nitrogen-free extract

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16
Q

Dry matter (DM)

A

Material remaining after removal of moisture

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17
Q

Why is accurate DM values important

A

Allows comparisons of the nutrient composition among different feeds

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18
Q

What is the most common method to measure the moisture content of feed

A

Drying a known weight of food to constant weight at 105C

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19
Q

How is crude protein content calculated

A

From the total nitrogen multiplied by a specific factor

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20
Q

How is total nitrogen often determined

A

By the Kjeldahl or dumas combustion method

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21
Q

What is the factor that N content is multiplied by to get crude protein

A

5.3-6.38 (originally 6.25 based on the assumption that proteins contain 16 percent N)

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22
Q

Why is crude protein not true protein

A

The methods for determining it use N from sources other than protein, such as free amino acids, amines and nucleic acids

23
Q

Explain the Kjeldahl procedure

A

Organic matter is digested with concentrated sulphuric acid
Catalyst mixture is added
All N is converted to ammonia (except nitrate/nitrite)
Ammonia ionized to ammonium
Ammonium is collected and measured colorimetrically/by titration

24
Q

Explain the Dumas/combustion method

A

Sample is combusted
N is converted to N gas
Other volatile compounds are trapped and separated
Measures N gas

25
Q

What are some downsides to the Kjeldahl method

A

Time consuming and involves the use of hazardous chemicals

26
Q

What are some downsides to Dumas method

A

Expensive

27
Q

Ether extraction

A

Ground dry samples are extracted with diethyl ether for more than 4 hours
The residue after evaporation is the ether extract

28
Q

Ether soluble materials include…

A

A large variety of organic compounds, many of which may not have nutritional significance

29
Q

Crude fiber is determined by…

A

Using the ether extracted sample, boiling in dilute acid, dilute base, filtering, drying and burning in a furnace

30
Q

Crude fiber fraction

A

Different in weight before and after burning

31
Q

Crude fiber contains…

A

Cellulose, hemicellulose and lignin.

32
Q

Ash

A

The residue after all combustible material has burned off - inorganic matter in feed

33
Q

Ash in feed samples comes from…

A

Minerals in plant cells, added minerals, soil contamination, or from biogenic silica

34
Q

Organic matter is calculated as…

A

The difference of its dry matter and ash content, expressed as a percent

35
Q

Nitrogen free extract is determined by…

A

The difference between the original sample weight and the sum of the weight of moisture, crude protein, ether extract, crude fiber and ash

36
Q

NFE is made primarily of…

A

Readily available carbs (sugars, starches, fructans, pectins and organic acids), and hemicellulose and lignin

37
Q

What is a major drawback of NFE

A

It is calculated as a difference, so it is prone to large errors

38
Q

Fiber commonly refers to…

A

Hemicellulose, cellulose and lignin

39
Q

Neutral detergent extraction (NDF) contains…

A

Cellulose, hemicellulose, and lignin (major cell wall components)

40
Q

In NDE, the nonsoluble material is…

A

The NDF

41
Q

Why are amylase and sulfite used in NDE

A

Amylase removes starch and sulfite breaks disulfide linkages to remove proteins
This results in less contaminating material

42
Q

When is sodium sulfite not used in NDE

A

To produce residue on which neutral detergent-insoluble nitrogen can be measured

43
Q

Acid detergent fiber is composed of…

A

Cellulose, lignin and acid detergent-insoluble nitrogen (ADIN)

44
Q

Why is ADF useful for forages

A

There is a good correlation between in and forage digestibility

45
Q

ADIN an be used to estimate…

A

undigestible or heat-damaged protein in feeds

46
Q

What are some properties of lignin

A

Reduces the digestibility of the cell wall carbs it is associated with
Linked to plant cell wall components

47
Q

How do you determine acid-detergent lignin

A

The ADF fraction is treated with concentrated sulfuric acid, dissolving cellulose
The residue is ashed and determined crude lignin

48
Q

What are 2 ways to determine amino acid composition in feedstuff

A

HPLC or IEC

49
Q

Maillard reaction

A

Reduces biological value of protein, lysine becomes nutritionally unavailable

50
Q

What 2 groups are used to measure the sugar fraction

A

WSC and 80% ESC (WSC preferred bc of fructans)

51
Q

What is NIR spectroscopy

A

Involves shining NIR light on ground feed samples and detecting the reflected light

52
Q

What is the wave length of NIR

A

730-2500nm

53
Q

NIR should only be performed on feed samples for which…

A

Adequate calibrations (known curves) are available

54
Q

What are some benefits to NIR

A

Useful, less time, less expensive than chemical analyses

Animal Nutrition & Metabolism (4 decks)

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