CHEMICAL ANALYSIS OF FEEDSTUFFSPages 87-93

Question• Why have some foreign feed companies added the

compound below to some feed ingredients?

A) Increase the energy concentration B) Increase the crude protein concentration C) Supply an essential amino acidD) Supply a required vitamin

NH2

C

N N

C C

NH2 N NH2

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

• 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

• 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 feedstuffsDM,%

<30 30-60 60-75 68-75 >82

Putrefaction Ensiled forages

Mold & heating

High moisture grains

Dry grains and baled forages

• 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 NSample→Boil in conc. H2SO4→(NH4)2SO4→Add conc. NaOH, → Titrate distill NH3, and trap NH4 borate in boric acid

• N analyzerSample→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. Chains of amino acidsB. AmmoniaC. BiuretD. UreaE. 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. Chains of amino acidsB. AmmoniaC. BiuretD. UreaE. 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 90Feather 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 DigestibilityWell-preserved alfalfa hay 18 90Heat-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– ProcedureSample→Extract with AD→ADF→Analyze N by Kjeldahl procedureADF-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?

A) Increase the energy concentration B) Increase the crude protein concentration C) Supply an essential amino acidD) Supply a required vitamin

NH2

C

N N

C C

NH2 N NH2

Melamine