• Needed to rationally group feed nutrients and requirements
– Makes analysis relatively easy and cost-effective
•
– Proximate analysis system (Weende system)
• Developed in 1864 at Weende Experiment
Station in Germany
– Detergent analysis system (Van Soest system)
• Developed in 1964 at USDA Beltsville Research
Center

• Dry matter
• Ash
• Crude protein
• Ether extract
• Crude fiber
• Nitrogen-free extract

•
– Material remaining after a feed is dried in a
100 o C oven for 24 hours
• DM,% = wt after drying/wt before drying x 100%
• % moisture = 100 – DM,%
– Problems with method
• Errors from losses of volatile components
– Particularly a problem with fermented feeds
– Can be avoided by toluene distillation or freeze drying
• Drying at 100 o C destroys sample for further analysis
– Can be avoided by freeze drying or drying at 65 o C for
48 hours in preparation for analysis (Still need to run a total DM analysis of part of sample)

• Significance of DM
– Considerable variation in the DM, % of feedstuffs
• Corn grain, 88% DM
• Alfalfa hay, 90% DM
• Alfalfa silage, 45% DM
• Alfalfa pasture, 26% DM
• Whey, 7%
– Other nutrients are present within the dry matter
• Affects expression of concentrations of nutrients in feedstuffs
• Example Crude protein, %
DM,% Wet basis DM basis
– Dried distillers grains 93 27.9
30
– Modified distillers grains 50 15.0 30
– Wet distillers grain 40 12.0 30
– Affects storage properties of feedstuffs

•
– Material remaining after oxidation of a sample at 600 o C for 2 hours in a muffle furnace
• % Ash = wt after ashing/sample wt x 100%
• % Organic matter = 100 - % ash
– Problems
• No indication of amounts of individual minerals
• Some minerals (Sulfur, Selenium, Zinc, Iodine are lost)
– Significance
• May indicate soil contamination or adulteration of feedstuff or diet.

•
– % Crude protein = %N x 6.25
– %N determination
• Kjeldahl N
Sample→Boil in conc. H
2
SO
4
→(NH
4
)
2
SO
4
→Add conc. NaOH, → Titrate distill NH
3
, and trap NH
4 borate in boric acid
• N analyzer
Sample→Pyrrolize sample at high temp.→Measure N
2 w/detector
– Factor of 6.25 assumes that most proteins contain
16% N
CP,% = measured mg N/100 mg sample x 100 mg protein/16 mg N
= measured mg N/100 mg/sample x 6.25

• Problems with crude protein procedure
– Sources of N
• True protein
– Chains of amino acids bound by peptide linkages
– Can meet the protein requirements of either nonruminant or ruminant animals
• Nonprotein nitrogen
– Forms
» Free amino acids
» Nucleic acids
» Ammonia
» Urea
» Biuret
– Can meet the protein requirements of ruminant animals
» Urea and biuret commonly added to ruminant diets
– Can not meet the protein requirements of nonruminant animals
– Says nothing about the amino acid composition of the feed source
• Commonly assume that the concentration of individual amino acids is constant within the protein a given feedstuff
• Can analyze for individual amino acids

– Crude protein says nothing about the digestibility of a protein
• Varies with feedstuff
Soybean meal
% Crude protein % Protein Digestibility
45 90
Feather meal 80 75
• Varies with heat damage
– When overheated, protein will bind to the cell wall carbohydrates particularly across lysine
– Causes
» Molding of forages
» Over-heating during processing
» Over-drying of grains or soybeans
– Referred to as the Maillard or Browning Reaction
– Results
% Crude protein % Protein Digestibility
Well-preserved alfalfa hay
Heat-damaged alfalfa hay
18
18
90
60

•
– Also called crude fat
– Material removed by refluxing ether through a feed sample for 4 hours
% Ether extract = (Sample wt-residue after ether extract)/Sample wt x 100%
– Theoretically represents fat content of the feedstuff
• A high ether extract content should indicate a high energy concentration
– Problem with procedure
• Ether extract consists of:
– True lipids
» Fats and oils
– Non-nutritional ether soluble components
» Fat-soluble vitamins
» Chlorophyll
» Pigments
» Volatile oils
» Waxes

•
– Procedure
Sample→Extract with dilute H
2
SO followed by dilute NaOH
4
→Residue→Burn at 600 o C→Ash
% CF = (Residue wt-Ash wt)/sample wt x 100%
– Theoretically represents
• the structural carbohydrates (Cellulose and hemicellulose)
– Limited digestibility in ruminants
– Poor digestibility in nonruminants
• Lignin
– Indigestible by ruminants and nonruminants
– Problems with procedure
• Poor recovery of components
– Lignin
% recovered
– Cellulose 90
– Hemicellulose 50-60
13-70

•
– No actual analysis
– Calculation by difference
• %NFE = %DM – (%ash+%CP+%EE+%CF)
– Theoretically represents:
• Starch
• Sugars
– Problems:
• Contains all of the errors from other analyses
– Largest error is unrecovered lignin will be placed in
NFE

• Neutral detergent fiber (NDF)
– Consists of hemicellulose, cellulose, lignin, cell wall bound protein and insoluble ash
– Significance:
• Highly related to feed intake
• DMI, % BW = 120/% NDF
• Acid detergent fiber (ADF)
– Consists of cellulose, lignin, poorly digested protein, and insoluble ash
– Significance:
•
• Highly related to digestibility and energy concentration
• DDM% = 88.9 – (.779 x %ADF)
NE l
, Mcal/lb (for legumes) = 1.011 – (0.0113 x %ADF)
– Combination of DDM (determined from ADF) and
DMI (determined from NDF) is used to determine
Relative Feed Value (RFV)
• RFV=DDM x DMI / 1.29
• Used for hay marketing

– Nitrogen bound to acid detergent fiber is a measure of heat-damaged protein
• Called ADIN or ADF-CP
– Procedure
Sample→Extract with AD→ADF→Analyze N by
Kjeldahl procedure
ADF-CP, % of total CP= %ADFN x 6.25/%CP x 100%
– Relationship to protein digestibility (called adjusted
CP)
• If ADF-CP, % of total CP <14, ADIN is considered digestible
– Adjusted CP = CP
• If ADF-CP, % of total CP is >14 and <20
– Adjusted CP = ((100 – (ADF-CP, % of CP – 7))/100) x CP
• If ADF-CP, % of total CP is > 20
– Adjusted CP = CP – ADF-CP, % of CP

• N bound to NDF and ADF used to determine rumen degradable, rumen undegradable, and indigestible fractions
Rumen degradable protein = Total CP – (NDFCP, % of CP xTotal CP)
Rumen undegradable protein = (NDFCP, % of CP xTotal CP) –
(ADFCP, % of CP xTotal CP)
Indigestible protein = (ADFCP, % of CP xTotal CP)

• Near infrared reflectance spectroscopy
– Determines the concentrations of protein, amino acids, lipids, and carbohydrates based on absorption of near infrared light
– Advantages
• Rapid
• Used by most commercial labs
– Limitations
• Requires calibration
• Inability to measure heterogeneous molecules like lignin
• Inability to measure minerals

• Atomic absorption spectroscopy
– Used for mineral analysis
– Procedure
• Sample ashed and extracted into a solvent
• Dissolved sample sucked into a flame with a light at a specific wavelength going through it
• Absorption of light directly proportional to absorption of light
– Limitation
• Expense
• High performance liquid chromatography
– Used of amino acids and vitamins
– Procedure
• Sample dissolved in organic solvent injected into column
• Column differentially separates components
• Detector measures components as they through the column
– Limitation
• Expense