1.
a.
Given his current breeding program and a 50:50 malefemale birth ration, there will
be 100 calves total; 50 male calves and 50 female calves.
b.
Since there are 50 males in the herd and the top 8% are selected for, the selection
intensity would be 1.86 standard deviation units.
2.
a.
The selection intensity in his older females is .35 standard deviation units.
b.
The effective selection intensity in his heifers is 1.40 standard deviation units.
c.
The overall effective selection intensity in his females is 0 standard deviation units.
3.
a.
20 heifers are 3 years old and 80 older cows are 60 years old; the generation interval
is 5.4 years.
b.
The generation would only change by a small amount,
.2 years
(5.45.2=.2 years).
4.
The ration from 2 to 3 years would be 5.2:5.4; this would have a minute impact to
selection based on yearling weight because he selects on YW. (The impact would only be
.2 years.) At 2 years of age, the heifers may not have reached their full potential in
regards reproduction status as well as providing the adequate amount of nourishment for
their young.
5.
a.
Sqrt(.25)=
.5
b.
[2(.25)(1)/(4+(11).25)]=.125
Sqrt(.125)=
.35
6.
a.
The rate of genetic change will be faster; improvement will be faster.
b.
Rate of genetic change in the overall herd population will not be as fast as the
females; however, but genetic change will come sooner than it did before in the
overall herd.
7.
[(.25)(1.86)(80)/3]=
12.4 lbs/yr
8.
a.
Since he is selecting for the top 10%, the standard deviation would be 1.76.
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 Spring '09
 HAY
 Genetics, Standard Deviation, bulls, Selective breeding, Breed, Hybrid vigor

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