NUT 115-Midterm 2 Exam Questions With
Correct Answers
The use of laboratory techniques to determine the concentration of nutrients(and energy) in a
feedstuff or diet - answer✔Chemical evaluation
The use of animals, in some way, to measureutilization of nutrients from a given feedstuffvor
diet - answer✔Biological evaluation
What is the first step of chemical evaluation? - answer✔getting a representative sample
What are the 3 selections of analytical methods in chemical evaluation? - answer✔1-Proximate
Analysis
2-Van Soest Detergent Fiber Analysis
3-Near-Infrared Spectroscopy (NIRS)
How many categories for particle compounds are there in proximate analysis?
-list them - answer✔1-Water
2-Crude Protein
3-Ether Extract (crude fat)
4-Crude Fiber
5-Ash
6-Nitrogen Free Extract (NFE)
Proximate analysis pitter - answer✔
How long are samples heated at what temperature in proximate Analysis-Moisture (water)? -
answer✔105 °C for 24 hours
What is the formula for % moisture for Proximate analysis-Moisture (water)? - answer✔(Weight
of water loss/Weight of original sample) x 100
What is the formula for % dry matter for Proximate analysis-Moisture (water)? - answer✔DM=
100 - moisture
What is a source error for Proximate analysis-Moisture (water) - answer✔may overestimate
moisture (underestimate DM ) from loss of volatile compounds in
What are alternative methods for Proximate analysis-Moisture (water)? (2) - answer✔1-drying
under vacuum
2-freeze-drying
What basis assumes no water is present. This expression of nutrient composition allows to
accurately compare the nutrient composition of the various feedstuffs. - answer✔Dry Matter
Basis
What basis represents feed as it would be fed to the animal, including water? - answer✔As-fed
basis
What basis describes when feeds are allowed to air dry, most feeds eventually equilibrate to ~
90% dry matter (~ 10%moisture)? - answer✔Air-dry basis
What are the 2 rules for Dry-matter and As-fed Conversions? - answer✔1-The percentage of a
nutrient on a dry matter basis will always be higher than it will be on an as fed basis
2-The amount of feed on a dry matter basis will always be lower than the amount of feed on an
as-fed basis
SEE pg 11 for equations
What is the importance of water or dry matter in Proximate analysis - Moisture(water)? (4) -
answer✔1-Proper moisture concentration for storage
2-Dry matter gives a basis to describe the quantity of feed consumed
3-Water is diluent of the other feed components
4-Moisture level affects the economic value of feedstuff
What 5 things does grinding an air dry sample produce for chemical/proximate analysis? -
answer✔1-Crude Fiber
2-Ether Extract
3- Crude Protein
4- Ash
How do you prepare a sample for proximate analysis? (2) - answer✔1- Dry 55-60 °C)- only
needed for wet/high moisture sample
2-Grind (1mm particle size) in Wiley mill
What does Proximate analysis-Ash represent? - answer✔the total mineral content (inorganic
portion) of the feed
What is the method of Proximate analysis-Ash? - answer✔Combust sample at 500-600°C for 4
hours in muffle furnace
What is the source of error for Proximate analysis-Ash? - answer✔The hightemperature may
volatilize someminerals such as chlorine, zinc,selenium and iodine.
What are the implications of ash content? (3) - answer✔1-Ash tells you nothing about the
concentration of individual minerals
2-Ash may indicate soil contamination
3-Ash acts as diluent of other nutrients (and energy)
What are the 4 steps in Proximate analysis - Crude Protein (Kjeldahl method)? - answer✔1-
Digest small dried sample in concentrated sulfuric acid until allorganic matter is destroyed
2-Nitrogen from feed is now in the form of ammonium sulfate((NH 4) 2SO 4)
3-Ammonia (NH 3) is liberated by adding sodium hydroxide to thedigest, distill off and collected
in standard acid
4-The quantitative content of nitrogen is determined by titrationwith sulfuric acid or
hydrochloric acid.
T/F In Proximate analysis - Crude Protein(Kjeldahl), Amino acids are the only nitrogen-
containing components of the feed - answer✔False
-nucleic acids and nucleotides (20%
-Vitamins, amines, amides, urea, and other substances(10%)
What is the alternative to the Kjeldahl method? - answer✔Dumas combustion method
What are the 3 steps of Dumas combustion method? - answer✔1-The sample undergoes
oxidation by "flash combustion"
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