Feedstuff Evaluation Methodology

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Feedstuff Evaluation Methodology
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The First Step

• Know the nutrient composition of your feed
  ingredients!
• Discuss the way we determine nutrient
  concentration in feedstuffs

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Key to Nutrient Analysis

• The analysis is only as good as the sample you
  take !!!
• 1 quart sample has to represent several tons of
  feed/feedstuff
• representative sample

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Sampling Feedstuffs

• ID label containers with your name, address,
  date, and feed type, etc.
• Sampling
• Grain or mixed feeds
• Sacks 2 handfuls from 5-7 bags
• Bulk 12-15 samples from different areas
• Random samples placed in bucket mixed
• Obtain uniform subsample

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Sampling Feedstuffs

• Hay
• Use a hay probe take 12-15 samples from all
  locations/depths
• Cut samples into 1-2 lengths mix in clean
  bucket
• Haylage or Silage
• Collect samples during the entire loading process
  for new
• For old, take series of samples (not spoiled)

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Sampling Feedstuffs

• Grain send in at least 1 pt
• Hay send in at least ½ lb
• Silage (Wet Feedstuffs) 2 qts in an airtight
  container, preferably freeze or refrigerate, or
  deliver immediately
• Samples must arrive at lab in same condition they
  left your farm!

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Why analyze rations or feedstuffs??
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Nutrient Analysis

• Book values are averages over many locations
• Your region may differ in the nutrient density of
  the feedstuffs it produces
• Example Book value for SBM 48 CP
• Your SBM from SD 46.5 CP
• Overfeeding/underfeeding nutrients
• Contaminants in feedstuffs
• Toxins, chemical residues, or other harmful
  compounds

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Nutrient Analysis

• How often should you analyze your
  feedstuffs/rations?
• Every time you change batches/loads of feedstuffs
• When you change feedstuffs in your rations
• Every time you mix a new batch of feed
• Monthly samples of forages/silages
• In a perfect world
• Generally, take sample after harvest

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Analysis Systems
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Analysis Methods

• 1. Chemical
• e.g. titration, chromatography (chemistry)
• No estimate of utilization, lab errors
• 2. Biological
• Animals Expensive tedious
• Difficult to obtain individual nutrient effects
• 3. Microbiological
• Microorganisms estimations
• Accurate quantification difficult

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Proximate Analysis

• Traditional standard of the industry
• Developed in Germany more than a century ago
• Most generally used chemical scheme for
  describing feedstuffs
• Limitations for todays diet formulation systems
• Information is of uncertain nutritional
  significance
• May result in misleading results

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Proximate Analysis
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Dry Matter

• Weigh a sample
• Heat to 100 105 C
• Re-weigh the sample
• Difference in 2 weights is water loss
• DM 100 - water loss

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Ash

• Weigh a sample
• Burn for 2 hrs at 600 C (1112 F)
• Weight remaining is ash
• Individual minerals not determined
• Use atomic absorption, spectrophotometry to get
  individual minerals

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Ashing Oven
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Crude Protein

• Kjehdahl Method
• Digest a dry sample in concentrated sulfuric acid
• Converts N to ammonium
• During distillation ammonium is converted to
  ammonia
• mL of acid used to bring ammonia solution to
  neutral pH amount of N in sample
• Total N x 6.25 CP

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Digestion Process
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Distillation Process
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Kjehdahl Method

• Important Point
• Analysis does not distinguish between N sources
• Protein
• Synthetic amino acids
• Non-protein N (urea, NH4, biuret)

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Crude Protein

• Combustion Method (LECO)
• N is released at high temperature in presence of
  pure O2
• N determined by thermal conductivity within the
  instrument
• EXPENSIVE equipment!

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LECO analyzer
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Ether Extract

• Fat determination
• Boil sample in ether alcohol to extract lipid
  fraction of sample

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Crude Fiber

• Industry method for fiber determination
• BUT--80 of hemicelluloses, 60 of lignin, and as
  much as 50 of celluloses can be lost
• CF value lower than actual amount of fiber in
  feedstuff
• Lignin can attach to N
• Overestimated lignin

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Van Soest Method of Forage Determination
Replaces CF Analysis
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Van Soest Fiber Determination

• Used to determine the insoluble cell wall matrix
  the major subcomponents
• 1. Hemicellulose
• 2. Cellulose
• 3. Lignin
• Able to determine heat-damaged protein
• Maillard Products
• N content of ADF fraction (ADINindigestible N)
• Tells you the amount of N in a sample that is
  actually AVAILABLE to the animal for use

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Detergent System
Ground forage sample
Digest with neutral detergent (ND)
ND insoluble fiber (NDF) (cell wall components)
ND solubles (cell contents)
Digest in acid detergent (AD)
AD insoluble fiber (ADF) (cellulose, lignin)
AD solubles (hemicellulose, cell wall N)
Digest with 72 H2SO4
Acid insoluble lignin
Solubles (cellulose)
Lignin by loss of ignition
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Detergent Digestion System
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Summary

• NDF hemicellulose cellulose lignin
• ADF cellulose lignin
• ADL lignin

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Near Infrared Reflectance Spectroscopy (NIRS)

• Based on Each major chemical component has a
  near infrared absorption property that
  distinguishes each component
• Absorption is affected by Atom vibration
  velocity
• Works for most common feeds
• Questionable
• Feeds from abnormal conditions (drought)
• Mixed feeds

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Near Infrared Reflectance Spectroscopy (NIRS)

• Advantages
• 1. Speed (lt 30 sec - 3 min)
• 2. Simplicity of sample preparation
• 3. Analyze multiple components in one
• operation
• 4. Does not consume the sample
• 5. Cheap

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Near Infrared Reflectance Spectroscopy (NIRS)

• Disadvantages
• 1. Expensive, high-precision instrumentation
• 2. Dependence on calibration procedures
• 3. Inability to measure minor constituents
• i.e. minerals
• Still a developing technology
• Gaining popularity

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Others

• Vitamins
• Individual assays for each vitamin
• Chemical/biological assays using chromatography
• Minerals
• Assays to obtain concentration of individual
  minerals
• Using Atomic Absorption Spectrophotometry

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Energy Determination

• Total digestible nutrients (TDN) vs. Bomb
  Calorimetry
• Explained in Energy Systems

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Feedstuff Evaluation

• RememberChemical analysis is the starting point
  for determining the nutritive value of feeds
• The actual value of ingested feedstuffs is
  dependant upon the ability of the body to make
  use of the nutrients in the feedstuff

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Feedstuff Evaluation

• Two general classifications of methods
• In vitro methodology Simulate digestion in a
  test tube to estimate nutrient digestibility
• In vivo methodology Feed animal and measure
  response criteria
• Growth
• Retention/Excretion
• Digestibility

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In vitro methodology

• Method to estimate digestibility of feedstuffs
• Uses enzymes and (or) microorganisms in a test
  tube to simulate GIT environment
• Method is cheap, with results in about 24 - 48
  hours
• Rough estimate of digestibility

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In vitro methodology
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In vitro methodology

• Use enzymes to simulate digestion in upper GIT
• Mouth
• Stomach
• Small Intestine
• Use fecal inoculant to simulate fermentation in
  lower GIT
• Large Intestine

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In vivo methodology

• Feeding trials
• Simply give an indication of
• Palatability of feedstuff in a ration (will the
  animals eat it?)
• Growth response compared to another
  feedstuff/ration
• Tells NOTHING of why different results were
  obtained

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Feeding Trials
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Feeding Trials
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In vivo methodology

• Metabolism Trial
• Determines nutrient retention/excretion
• Complete analysis on ration
• Feed known amount to animals
• Collect urine/feces
• Compete analysis on urine/feces

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Metabolism Trial
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In vivo methodology

• Metabolism Trial
• Calculation (In Out)/In 100

Nutrient retention Nutrient intake Nutrient
excretion (Urine Feces) x 100 Nutrient
intake
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In vivo methodology

• Digestibility studies
• Use of cannulated animals
• Can determine small intestinal digestibility
  (hydrolytic digestion) as well as total tract
  digestibility (hydrolytic fermentative
  digestion) of nutrients

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Cannulated Animals
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Cannulated Animals
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Cannulated Animals
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Cannulated Animals
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Cannulated Animals
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In vivo methodology

• Digestibility studies
• Effluent from small intestine or rumen or feces
  is collected and analyzed for nutrient(s) being
  studied

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In vivo methodology

• Digestibility studies
• Collection at terminal SI is referred to as ileal
  digestibility
• Collection of feces determines total tract
  digestibility

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In vivo methodology

• How is TRUE digestibility determined?
• Usually only in monogastrics
• Usually only concerned with true AA digestibility
• Chickencectomized animals
• Surgically remove ceca from birds and measure
  digestibility
• Pigsfeed diet containing no protein

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In vivo methodology

• Determination of endogenous losses
• Endogenous losses
• Sloughed intestinal cells
• Sloughed microbial cells
• Enzymes
• Mucin
• Measure AA output from protein-free diet
  endogenous losses
• Corrects for AA present but not of feed origin

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In vivo methodology

• In-Situ digestibility
• Digestibility within a localized area or position
• rumen, abomasum, small intestine
• Use cannulated animals
• Mesh bag to contain the feedstuff and allow
  microbial action to take place
• Determine
• Rate/extent of digestibility