Chapter 2 Handout

Chapter 2 Handout - Chapter 2 Evaluating Feedstuffs for...

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Chapter 2 Evaluating Feedstuffs for Farm Livestock
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Good Feed Sample Randomly taken. Represents the feed: Grain: probe Hay: core-sampler Well preserved. Approximately 1 lb. needed.
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Evaluating Feeds Feed microscopy Evaluating feed samples under a microscope. Determine presence or absence of ingredients. Can see unwanted materials. Mainly for regulatory purposes. Feed Analysis Proximate analysis: standard chemical method.
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Proximate Analysis (pg. 96) Dry Matter Crude Protein Ether Extract Ash Crude Fiber Nitrogen-Free Extract
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Dry Matter Drying the feed sample to a constant weight. (Wet weight-dry weight)/ wet weight * 100= %DM 100- %mosture = %DM Important because: Many feeds have high moisture content. Silages, food processing waste, etc. Quality and value depend on how much water. Feed analysis performed on dried samples. However, producer or nutritionist must know as-fed (or as-is) basis for nutrients.
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Converting DM to As-Fed DM to as-fed: Multiply b %DM divided by 100. Example: DM basis, alfalfa sample is 16.5% CP. DM=92% CP as-fed = 16.5 x (92/100) = 16.5 x 0.92 = 15.2% As-fed to DM: Multiply by 100 divided by %DM Example: As-fed basis barley sample is 11.2%CP. DM of the barley sample is 96% CP DM basis = 11.2 x (100/96) = 11.7% Remember: values are always higher on DM basis.
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DM: As-Fed Calculations Examples in book pg. 100-1 Can use equation to set up a proportion. Alfalfa silage: 7% CP, 40% DM. What is CP on a dry matter basis: %nutr. As-fed% / %feed DM = % nutr. DM basis / 100% DM 7/40= x/100 40x= 700 X= 17.5%
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Reporting Feedstuff Composition As-Fed Dry Matter Air-Dry (90% DM)
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Crude Protein: Kjeldahl Analysis N content * 6.25 Why 6.25? Factor derived from generalization that most proteins contain 16% N. 100/16=6.25 N determined by Kjeldahl procedure Named for Danish chemist.
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Kjeldahl Procedure Sample boiled in sulfuric acid. Complete oxidation of organic material
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This note was uploaded on 02/03/2009 for the course DARY 3010 taught by Professor Williams during the Spring '09 term at LSU.

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Chapter 2 Handout - Chapter 2 Evaluating Feedstuffs for...

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