Week 1

Feedstuffs and Nutritional Value

Laboratory-Based Analyses

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• Objective
• Measure amount of each component (nutrient) in feedstuff
• Accurate quantitative measurement
• Procedures
• Proximate analysis
• Figure 3.6 – Diagram of proximate analysis

 



• Dry matter (DM)
• Estimates quantity of dry matter and moisture content
• Crude protein (CP)
• Estimates quantity of protein and nonprotein nitrogen compounds
• Kjeldahl method to estimate nitrogen
• Nitrogen converted to CP
• Equation: % CP = Nitrogen x 6.25
• Ether extract (EE)
• Estimates quantity of organic solubles; lipids
• Ash
• Estimates quantity of inorganics; minerals
•  Crude fiber (CF)
• Estimates quantity of fiber associated components, i.e. cellulose, hemicellulose, and lignin
• Unsatisfactory; replaced by detergent fiber analysis
• Nitrogen-free extract (NFE)
• Estimates nonfibrous carbohydrates
• Calculation
• %NFE = 100 % DM –
• Detergent fiber system
• Figure 3.7 – Diagram of detergent fiber system



• More accurately estimates CHO fractions
• Estimates of fibrous CHO
• Neutral detergent fiber (NDF)
• Primarily: hemicellulose, cellulose, and lignin
• Acid detergent fiber (ADF)
• Primarily: cellulose and lignin
• Estimates of nonfibrous CHO
• Nonfibrous carbohydrates (NFC)
• Calculated
• %NFC = 100 % DM –
• Gross energy (GE)
• Estimates total chemical energy
• Figure 3.8– Diagram of bomb calorimeter



• Inconsistent measure of energy available
• Used with additional procedures
• Specialized procedures
• High performance liquid chromatography (HPLC)
• Identify amino acids
• Atomic absorption spectrophotometry
• Identify minerals
• Near-infrared reflectance spectroscopy (NIRS)
• Standard analyses
• Gas-liquid chromatography (GLC)
• Identify gaseous compounds and compounds able to be vaporized