Selection Response

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Lecture 22
Selection Response
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Distribution of EBVs
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Distribution of EBVs
females
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Distribution of EBVs
males
females
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Selection Response

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Selection Response
?Gm response to selection of males per
generation (?Gf for females)
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Selection Response
?Gm response to selection of males per
generation (?Gf for females) response
change in the average genetic merit
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Selection Response
?Gm response to selection of males per
generation (?Gf for females) response
change in the average genetic merit ?Gm
intensity of selection (im) X accuracy of
evaluation (rmBV,EBV) X standard deviation
of BVs (?BV)
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Selection Response
?Gm im rmBV,EBV ?BV
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Selection Response
?Gm im rmBV,EBV ?BV ?Gf if rfBV,EBV
?BV
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Selection Response
?Gm im rmBV,EBV ?BV ?Gf if rfBV,EBV
?BV ?G ?Gm ?Gf 2 total response
per generation
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Selection Response
?g response to selection per year
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Selection Response
?g response to selection per year ?Gm
?Gf Lm Lf
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Selection Response
?g response to selection per year ?Gm
?Gf Lm Lf L generation interval
average age of the parents for progeny born
in a year
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3 of 4 Components can be Manipulated
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3 of 4 Components can be Manipulated --
intensity -- accuracy -- generation interval
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3 of 4 Components can be Manipulated --
intensity -- accuracy -- generation interval
sometimes conflicting
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Male Selection

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Male Selection
Example litter size progeny test Need two
males
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Male Selection
Housing for 50 females 10 males with 5
daughters 50 5 males with 10 daughters 50
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Male Selection
Housing for 50 females 10 males with 5
daughters 50 5 males with 10 daughters
50 2/10 versus 2/5 males-- different intensity 5
versus 10 progeny -- different accuracies
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Male Selection
--to achieve greater intensity sacrifice accuracy
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Female Selection

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Female Selection
Example 1st record -- 3 years of age 2nd
record -- 4 years of age
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Female Selection
Example 1st record -- 3 years of age 2nd
record -- 4 years of age Second record provides
more information hence increases accuracy, but
need a year more to get it. -- accuracy versus
generation interval--
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Intensity

P
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Intensity

P
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Intensity
a) selection differential (Ps - P)
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Intensity
a) selection differential (Ps - P) --average
phenotypic superiority
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Intensity
a) selection differential (Ps - P) --average
phenotypic superiority b) selection intensity
(i)
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Intensity
a) selection differential (Ps - P) --average
phenotypic superiority b) selection intensity
(i) i Ps - P ?P
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Intensity
a) selection differential (Ps - P) --average
phenotypic superiority b) selection intensity
(i) i Ps - P ?P -- standardize
superiority expressed in standard deviations
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Intensity
If the population is large , i is directly
related to the fraction saved.
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Intensity
If the population is large , i is directly
related to the fraction saved. saved i
(S.D.s) 90 .195
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Intensity
If the population is large , i is directly
related to the fraction saved. saved i
(S.D.s) 90 .195 50 .795
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Intensity
If the population is large , i is directly
related to the fraction saved. saved i
(S.D.s) 90 .195 50 .795 10 1.755
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Intensity
If the population is large , i is directly
related to the fraction saved. saved i
(S.D.s) 90 .195 50 .795 10 1.755 1
2.660
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Comparing Selection Programs

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Comparing Selection Programs
Program 1
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Comparing Selection Programs
Program 1 A) Select males on their
performance. (h2 .36 for yearling weight)
?Gm (1.755)(.6) ?BV 1.053 ?BV
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Comparing Selection Programs
Program 1 B) Select females on their
performance rBV,EBV .6 Keep 80 gt if
.35
?Gf (.35)(.6) ?BV .210 ?BV
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Comparing Selection Programs
Program 1 C) Assume Lm Lf 4 ?Gm
(1.755)(.6) ?BV 1.053 ?BV ?Gf (.35)(.6)
?BV .210 ?BV and ?g 1.053?BV
.210?BV .158?BV 4 4
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Comparing Selection Programs ?BV 40
Program 1 C) Assume Lm Lf 4 If ?BV 40
lbs (.158)(40) 6.32 lbs per year
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Comparing Selection Programs
Program 2
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Comparing Selection Programs
Program 2 A) Select females the same. if
.35 rBV,EBV .6 Lf 4
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Comparing Selection Programs
Program 2 B) Progeny test males Still keep
10 gt im 1.755 Lm 6 instead of 4
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Comparing Selection Programs ?BV 40
To compare, first solve for the rBV,EBV for males
necessary to be equal. ?g 6.32 lbs
(1.755)rBV,EBV(40) .21(40) 6 4
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Comparing Selection Programs ?BV 40
To compare, first solve for the rBV,EBV for males
necessary to be equal. ?g 6.32 lbs
(1.755)rBV,EBV(40) .21(40) 6
4 Must solve for rBV,EBV
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Comparing Selection Programs
(6.32)(10) (1.755)rBV,EBV(40) .21(40)
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Comparing Selection Programs
(6.32)(10) (1.755)rBV,EBV(40)
.21(40) (1.755)rBV,EBV 1.37
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Comparing Selection Programs
(6.32)(10) (1.755)rBV,EBV(40)
.21(40) (1.755)rBV,EBV 1.37 rBV,EBV .78
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Comparing Selection Programs
(6.32)(10) (1.755)rBV,EBV(40)
.21(40) (1.755)rBV,EBV 1.37 rBV,EBV .78 How
many progeny to reach .78?
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Comparing Selection Programs
rBV,EBV aij bBVi on Pj ? (4 - .36)/ .36
11.1
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Comparing Selection Programs
rBV,EBV aij bBVi on Pj ? (4 - .36)/ .36
11.1 For PHS bBVi on Pj 2q and aij 1/2 q
?
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Comparing Selection Programs
rBV,EBV aij bBVi on Pj ? (4 - .36)/ .36
11.1 For PHS bBVi on Pj 2q and aij 1/2 q
? .78 1/2 2q q q ? q
? q 17.2 gt 18 progeny
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Comparing Selection Programs
-- Program 2 is better if we can get gt 18
progeny / bull. --