PREVIOUS ADS 520 EXAMS
ADS 520
Exam 3
May 25, 1995 Name____________________________
1. (4 pts) Why is lysine usually the first-limiting amino
acid in food and feed even though lysine is not the amino
acid found in the body in the greatest concentration? (You
will be graded on the clarity of your wording.)
2. (6 pts) When establishing the amino acid requirements for
growing pigs, the NRC committee found that there were many
discrepancies among estimates of requirements, and for some
amino acids there were few or no data for some stages of
the pig's life cycle. What did the NRC committee do to
circumvent this problem and estimate the amino acid
requirements? At least one (preferably two) amino acid(s)
must be mentioned in answering this question.
3. (8 pts) Given below is the requirement of selected amino
acids for feeder pigs weighing 10-20 kg and the amino acid
composition of milo. All values are given as a percentage
of the diet (requirement) or feed (milo). Give the order
of limiting amino acids for milo (#1 = most limiting; #2 =
2nd most limiting, etc.)
Lys Met + Cys Thre Tryp Ileu Leu Phe + Tyr
Required 0.95 0.48 0.56 0.14 0.53 0.60 0.78
Met Cys Phe Tyr
Milo 0.23 .16 .13 0.27 0.10 0.44 1.32 .49 .37
Leave the answer space blank if there is no limiting AA.
#1________ #2________ #3________
#4________ #5________ #6________
4. (3 pts) Define biological value in words. (Don't write
the equation.)
5, (2 pts) Corn protein has an apparent digestibility of 77
percent for pigs. The true digestibility of corn protein
would be (greater, the same, less). (Circle one.)
6, (2 pts) The biological value of casein fed to a growing
pig in a 10% casein diet was determined to be 90%. If the
BV had been determined using a 20% casein diet, it would
have been (higher, lower, the same). Circle the correct
answer. (Casein is 100% protein and was the sole source of
protein in the diet.)
7. (6 pts) Age and species are two factors affecting the
dietary essentiality of amino acids required by animals.
Name two amino acids whose essentiality are affected by
age: and .
What is different about the following species with respect
to essential amino acids:
Ruminants_______________________________________________
Chickens________________________________________________
Cats____________________________________________________
8. (4 pts) The swine NRC does not distinguish between gilts
and barrows when it lists the amino acid requirements for
growing and finishing pigs in Table 5-1. However, it is
stated in the text that amino acid requirements are
actually greater for one of these two sex classes. Which
has the greater amino acid requirement and why?
9. (4 pts) In the swine "Mixit" exercises in which feed-grade
lysine was available as an option, several students noted
that even though the requirements for all amino acids were
satisfied, the final diet "was still deficient in protein."
As the instructor, how should you respond to that comment?
10. (2 pts) In general, the amount of microbial protein
formed in the rumen is about (quantity with units)
____________________(Don't use Burrough's TDN conversion.)
11. (3 pts) Technically, dietary protein escapes fermentation
in the rumen; it does not by-pass the rumen. Give an
example of how dietary protein might "by-pass" the rumen.
12. (3 pts) To maximize feed utilization by ruminants we need
to match the degradability of proteins with the
availability of energy for rumen microbes. Match the
protein sources on the left with their appropriate energy
sources on the right. (Draw a line.)
Soybean meal Cellulose
Urea Cracked corn
Fishmeal Starch
13. (4 pts) If you want to purchase a protein supplement that
has a "relatively" high escape value (for ruminants) but
you do not have access to a publication listing the
degradability of protein sources, in general, what kind or
category of protein source would you look for? List 3 or 4
protein sources in this category that probably would fit
your needs. (Don't include fishmeal)
14. (6 pts) Soybean meal has an MP value of 171.6 g/kg and a
UFP value of -108.
a. What does the UFP value tell you? (Be factual and
specific)
_______________________________________________________
_______________________________________________________
We know that heating normal SBM reduces its degradability
in the rumen.
b. Would the UFP value of heated soybean be more negative
or less negative than normal SBM? Why?
_______________________________________________________
c. Comparing a corn-normal SBM diet to a corn-heated SBM
diet, which would most likely have the most microbial
protein produced in the rumen?
_______________________________________________________
Explain your rationale.________________________________
_______________________________________________________
15. (5 pts) When SBM is heated, the availability which amino
acid likely will be affected most? _______________________
Give the name of the reaction and explain what happens that
causes the decreased availability of this amino acid.
__________________________________________________________
What test is used to determined if heating might be
detrimental?
__________________________________________________________
16. (2 pts) When the UFP of a diet equals zero (neither
negative nor positive) using Burrough's system, what
terminology would we use (or what would we say) if using
Satter's system?
__________________________________________________________
17. (28 points) True or False. Circle the letter of the true
statements. If the statement is FALSE, correct the
incorrect word or phrase to make the statement true. (Your
correction needs only to indicate that you know why the
statement is false and does not have to make a correctly
worded sentence.)
Statements a r generally refer to nonruminants.
a. The NRC requirements for amino acids are for the l-isomer
only and are not adjusted for any d-isomers.
b. The NRC amino acid requirements are true minimal values
and are not adjusted for any differences in availability
(digestibility).
c. Pigs can use the D-isomer of added methionine in their
diet as effectively as the L-isomer.
d. Ruminant tissues require the same essential amino acids
as non-ruminants.
e. Phenylalanine can meet up to 50% of the tyrosine
requirements for pigs.
f. The amino acid requirements of growing-finishing swine,
expressed as percent of the diet, decrease as the
caloric density of the diet increases.
g. Of the essential amino acids, the one with the highest
dietary requirement is lysine.
h. The most toxic amino acid is arginine.
I. Sometimes the addition of a small quantity of an amino
acid to a diet can cause a growth depression; this is
called an imbalance.
j. Imbalances can be corrected by adding a certain amino
acid to the diet; this amino acid must be an essential
amino acid.
k. Antagonisms can be corrected by adding a certain amino
acid to the diet; this amino acid must be an essential
amino acid.
l. The measured PER of a protein will be greater if it is
fed at 10% of the diet than if it is 8% of the diet.
m. A protein having a low digestibility could have a higher
BV than one that has a high digestibility.
n. The biological value of a mixture of two proteins cannot
be greater than the BV of either of the component
proteins.
o. If energy in the diet is below the requirement, the
measured BV of the dietary protein will be greater than
its actual value.
p. Animals fed isonitrogenous diets will excrete more urea
if fed a protein having a low BV than if fed a protein
having a high BV.
q. Protein in the feces that is of body origin is referred
to as endogenous nitrogen loss.
r. One way to estimate endogenous nitrogen loss is to feed
the animal a protein-free diet.
The following statements refer primarily to ruminants.
s. When ruminants are fed low protein diets (near or
slightly less than their requirement) it is not unusual
to have more protein leaving the rumen than was in the
diet. (If false, explain why.)
t. We can alter the BV of microbial protein reaching the
intestines of cattle by feeding different types of grain
or changing the type of hay fed. (If false, explain
why.)
u. Because of the rumen microorganisms, the BV of high
quality proteins such as casein is decreased relative to
the animal's needs. (If false, explain why.)
v. When good feeding practices are used, enough microbial
protein is produced in the rumen to meet the protein
(amino acid) needs of the animal for maximum growth.
(If false, give the proportion of the requirement that
is produced.)
w. When ammonia-N concentration in the rumen is less than
about 5 mg/100ml rumen fluid, urea is equal to SBM as a
protein supplement. (Don't include lightweight feedlot
calves in evaluating this statement.)
x. When ammonia-N concentration in the rumen exceeds 5
mg/100 ml rumen fluid, 1 kg of crude protein equivalent
from urea equals only about 0.3 kg metabolizable
protein.
18. (6 pts) Cool-season annuals often contain 25-28% protein,
roughly double the requirement of stocker steers and
heifers, yet research has shown that cattle grazing these
forages may actually be protein deficient. Explain how
this statement can be true, and describe the supplement
program you would use of overcome this problem and maximize
the rate of gain.
A COUPLE OF PROBLEMS THAT WERE ON OTHER EXAMS:
01. (15 pts) Growing pigs in a nitrogen balance trial were
housed in metabolism cages to allow total collection of
feces and urine. They were fed 1800 g/day of a diet
containing 12.0% crude protein and gained 568 g/day. An
average of 234.2 g of feces were collected daily having
3.1% N and 2 liters of urine collected daily contained 5.46
g N per liter. When a protein-free diet was fed, the feces
contained 2.77 g N/day and the urine contained 5.5 g N/day.
Give the UNITS with all answers.
a. What is the PER of the protein as measured in this
trial? (2.63)
b. Calculate the true digestibility of the protein. (87.0%)
c. Calculate the biological value of the protein. (82.0%)
d. What is the NPU of the protein? (71.34%)
e. What is the best estimate of metabolic nitrogen losses?
(2.77 gm)
02. (15 pts) Calculate the metabolizable protein concentration
(gm MP/kg diet) for the diet given below. The MP, UFP, NEm
and NEg values given are the contributions of each
ingredient to the total diet. One kilogram of urea can
give rise to 2225 g MP.
Amount MP UFP NEm NEg
Ingredient % (g/kg) (g/kg) --(Mcal/kg)--
Corn grain........ 63..... 45.23.... +7.43... 1.44... .93
Crimson clover.... 18..... 9.59.... -5.76... .23... .12
cottonseed hulls.. 10..... 2.35.... + .38... .10... .02
Molasses.......... 6..... 1.37.... +1.21... .11... .07
Urea.............. 1 -- --
Additives......... 2 -- -- -- --
____ _____ _____ ____ ____
100 1.88 1.14
(As given, the diet contains 78.61 g MP/kg diet)
a. What percent, if any, of the urea in this diet would be
utilized? (32.6%)
b. How much more urea could be added to this diet? Express
your answer as percent of the diet. (None)
An alternative approach to the questions asked would be to
give information about a steer or heifer eating this diet,
have the student calculate the expected ADG based on NEm
and NEg, determine the MP required by that animal to
achieve that rate of gain, and have the student determine
if the diet provided enough metabolizable protein for the
animal.
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