Analysis of Feedstuff Flashcards
(54 cards)
Nutrient
Chemical element in the diet that is required for normal reproduction, growth, lactation, or maintenance of life processes
Analytical standard
A purified, known material or solution made from an analyte that is used in an assay and against which all sample results are compared to
Gravimetric analysis
Technique through which the amount of an analyte can be determined through the measurement of mass
What are the 2 general types of feed assays
Chemical analyses (wet chemistry) Near infrared (NIR) reflectance spectroscopy
What are 3 examples of chemical analyses
Gravimetric, spectrophotometric, chromatographic
What are 2 subdivisions of chemical analysis
Empirical fractions and specific analytes
Empirical fractions are defined by
The “fraction” or “extract” being measured
Often a mixture of compounds
Empirical assays tend to be…
Gravimetric (no analytical standard that represents a pure compound)
Empirical assays must be run using…
Standardized methods
What are the two main organizations responsible for the standardization of feed analysis
Association of Analytic Chemists (AOAC)
National Forage Testing Association
Specific analytes measure…
Specific, identifiable compounds
What are used as standards in specific analytes
Purified analytes
What are 3 types of chemical analysis that specific analytes can be measured by
Colorimetric, chromatographic, or spectroscopic
What is a proximate analysis
A combinator of analytical procedure, outdated, many limitations from a nutritional standpoint, still used by legislations for the declaration of the composition of foods in many countries
The proximate analysis divides the food into what 6 components
Moisture, crude protein, crude fat, crude fiber, ash, nitrogen-free extract
Dry matter (DM)
Material remaining after removal of moisture
Why is accurate DM values important
Allows comparisons of the nutrient composition among different feeds
What is the most common method to measure the moisture content of feed
Drying a known weight of food to constant weight at 105C
How is crude protein content calculated
From the total nitrogen multiplied by a specific factor
How is total nitrogen often determined
By the Kjeldahl or dumas combustion method
What is the factor that N content is multiplied by to get crude protein
5.3-6.38 (originally 6.25 based on the assumption that proteins contain 16 percent N)
Why is crude protein not true protein
The methods for determining it use N from sources other than protein, such as free amino acids, amines and nucleic acids
Explain the Kjeldahl procedure
Organic matter is digested with concentrated sulphuric acid
Catalyst mixture is added
All N is converted to ammonia (except nitrate/nitrite)
Ammonia ionized to ammonium
Ammonium is collected and measured colorimetrically/by titration
Explain the Dumas/combustion method
Sample is combusted
N is converted to N gas
Other volatile compounds are trapped and separated
Measures N gas
