Transcript chemical analysis of feedstuffs

CHEMICAL ANALYSIS OF
FEEDSTUFFS
Pages 87-93
Question
• Why have some foreign feed companies added
the compound below to some feed ingredients?
A)
B)
C)
D)
Increase the energy concentration
Increase the crude protein concentration
Supply an essential amino acid
Supply a required vitamin
FEED NUTRIENTS
FEED ANALYSIS SYSTEMS
• Needed to rationally group feed nutrients and
requirements
– Makes analysis relatively easy and cost-effective
• Feed analysis systems
– 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
PROXIMATE ANALYSIS COMPONENTS
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Dry matter
Ash
Crude protein
Ether extract
Crude fiber
Nitrogen-free extract
• Dry matter (DM)
– Material remaining after a feed is dried in a
100oC 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 100oC destroys sample for further
analysis
– Can be avoided by freeze drying or drying at 65oC for
48 hours in preparation for analysis (Still need to run
a total DM analysis on part of sample)
• Significance of DM
– Considerable variation in the DM, % of feedstuffs
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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
– Modified distillers grains
– Wet distillers grain
93
50
40
27.9
15.0
12.0
– Affects storage properties of feedstuffs
30
30
30
• Ash
– Material remaining after oxidation of a
sample at 600oC 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 (CP)
– % Crude protein = %N x 6.25
– %N determination
• Kjeldahl N
Sample→Boil in conc. H2SO4→(NH4)2SO4→Add conc. NaOH, → Titrate
distill NH3, and trap NH4 borate
in boric acid
• N analyzer
Sample→Pyrrolize sample at high temp.→Measure N2 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
• What form(s) of crude protein can be used to
meet the crude protein requirement of a 120
lb growing gilt?
A.
B.
C.
D.
E.
Chains of amino acids
Ammonia
Biuret
Urea
All of the above
• What form(s) of crude protein can be used to
meet the crude protein requirement of a 800
lb growing steer?
A.
B.
C.
D.
E.
Chains of amino acids
Ammonia
Biuret
Urea
All of the above
– Crude protein 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
% Crude protein % Protein Digestibility
Soybean meal
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
18
90
Heat-damaged alfalfa hay
18
60
• Ether extract (EE)
– 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
• Crude fiber (CF)
– Procedure
Sample→Extract with dilute H2SO4 →Residue→Burn at 600oC→Ash
followed by dilute NaOH
% 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
% recovered
– Cellulose
90
– Hemicellulose 50-60
– Lignin
13-70
• Nitrogen-free extract (NFE)
– 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
WHY IS PROXIMATE ANALYSIS SYSTEM
STILL USED?
DETERGENT ANALYSIS SYSTEM
• 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)
• NEl, 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)
• Traditional adjustment
– If ADF-CP, % of total CP < 10%
» Adjusted CP = CP
– If ADF-CP, % of total CP > 10%
» Adjusted CP = (100 – ADF-CP, % of CP) x CP
• Modern adjustment
– 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 X 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)
OTHER ANALYTICAL PROCEDURES
• 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
Question
• Why have some foreign feed companies added
the compound below to some feed ingredients?
Melamine
A)
B)
C)
D)
Increase the energy concentration
Increase the crude protein concentration
Supply an essential amino acid
Supply a required vitamin